PERICARP 
 INJURIES IN SEED CORN 
 
 Prevalence in Dent Corn and Relation to Seedling Blights 
 
 By Benjamin Koehler 
 
 BULLETIN 617 
 UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION 
 
Urbana, Illinois September, 1957 
 
 Publications in the I'ulletin series report the results of investigations made 
 or sponsored by the Experiment Station 
 
CONTENTS 
 
 PAGE 
 
 HISTORICAL REVIEW 6 
 
 GENERAL MATERIALS AND METHODS 7 
 
 Seed samples 7 
 
 Greenhouse and cold tests 11 
 
 Field tests 12 
 
 Statistical interpretation 12 
 
 OCCURRENCE OF PERICARP INJURIES 12 
 
 Prevalence in commercial seed 12 
 
 Effect of maturity and hybrid 15 
 
 Effect of mechanical shelling 18 
 
 EFFECT OF INJURIES ON SEEDLING GROWTH, STAND, 
 
 AND YIELD IN NATURALLY INFESTED SOIL 23 
 
 Seed with unsorted pericarp injuries 23 
 
 Importance of type of injury 24 
 
 Yield comparisons for similar stands 30 
 
 Effect of temperature 33 
 
 Effect of soil moisture 35 
 
 EFFECT OF INJURIES ON SPECIFIC SEEDLING BLIGHTS 36 
 
 Fungus isolations 36 
 
 Seed inoculation experiments 37 
 
 EFFECTIVENESS OF SEED TREATMENT 48 
 
 Effects on stand and yield 48 
 
 Importance of type of injury 49 
 
 Effect of temperature 51 
 
 Effect of injury after treatment 53 
 
 EFFECT OF PERICARP CONDITION ON RESISTANCE 
 
 TO SEEDLING BLIGHT 54 
 
 Resistance in inbreds 54 
 
 Resistance in single crosses 57 
 
 CONTROL OF SEEDLING BLIGHT IN DENT CORN 59 
 
 Avoidance of pericarp injuries 60 
 
 Seed treatment 61 
 
 Resistance in inbreds and crosses 61 
 
 DISCUSSION 62 
 
 SUMMARY 67 
 
 LITERATURE CITED 70 
 
ACKNOWLEDGMENTS 
 
 The author is indebted to the Illinois Crop Im- 
 provement Association, the Illinois Seed Pro- 
 ducers Association, the Plant Breeding Division 
 of the Agronomy Department, and numerous 
 seedsmen who furnished seed used in the 
 experiments reported here during the years in 
 which this research was carried on. 
 
PERICARP INJURIES IN SEED CORN: 
 
 Prevalence in Dent Corn and Relation to Seedling Blights 
 
 By Benjamin Koehler, Professor of Plant Pathology 
 
 MOST SEED PROCESSORS AND PRODUCERS seem to be 
 unaware of the large amount of pericarp damage in their seed 
 samples, and of the potential hazard to corn production. Corn is one of 
 the crops that are particularly susceptible to seedling blight when the 
 pericarp or seed coat is broken and not protected by a fungicide. In 
 order to protect seed corn from infection by soil organisms causing 
 seedling blight, practically all seed processors have adopted the practice 
 of treating their seed with a protective fungicide. However, the control 
 resulting from seed treatment has not been completely effective, and a 
 high prevalence of pericarp injury in the seed could still mean an 
 appreciable loss from seedling blight. 
 
 The occurrence of pericarp injuries in seed corn and their impor- 
 tance in respect to stand, yield, and resistance to seedling blight in 
 dent corn were studied over a period of years. Considerable atten- 
 tion was given in these studies to seed treatment and the degree to 
 which protective fungicides can limit the harmful effects of pericarp 
 , injury. Many samples of commercial seed from different sources were 
 examined for the extent and types of pericarp damage. Seed differing 
 in maturity, moisture content, and genetic constitution w r ere tested to 
 determine the degree to which these and other factors influence the 
 ! susceptibility of the seed to pericarp injury from mechanical hazards, 
 !■ and experiments in the field and cold tests were conducted to dis- 
 i tinguish between the various types of injury, according to their loca- 
 | tions on the kernel, in their effects on stand and yield in infested soil. 
 Resistance in inbreds was studied in relation to the pericarp condi- 
 tion of the seed, and experiments were conducted to determine if there 
 is any correlation between resistance to seedling blight caused by differ- 
 ent soil fungi. Several of these inbreds were then tested for their con- 
 I tribution to resistance or susceptibility in single crosses. 
 
6 Bulletin No. 617 {September, 
 
 Seed-corn processing plants were not investigated to determine 
 where and how injuries occur. To a large extent, each plant has de- 
 veloped its own system of handling the seed, and as a result the 
 problems of preventing pericarp injury differ. A limited study on the 
 occurrence of injuries in processing has been reported by Wortman 
 and Rinke ( 46). 
 
 HISTORICAL REVIEW 
 
 Meyers (35) as early as 1922 observed the importance of the peri- 
 carp in protecting seed corn against seedling blight infection. He inocu- 
 lated sound and pericarp-injured seed with an unidentified species of 
 Penicillium, planted them in field plots, and obtained striking reduc- 
 tions in stand and yield when the seed was injured. There have been 
 earlier reports (2) on the detrimental effects of pericarp injuries on 
 yield, but these did not mention any relationship between the injuries 
 and seedling diseases. 
 
 When open-pollinated corn was in general use, various experiments 
 were reported in which yield comparisons were made between seed 
 from smooth ears and seed from ears with rough indentations. Mont- 
 gomery (36), Cunningham (4), Manns and Adams (34), Holbert et al. 
 (11), Edgerton and Kidder (6), and others found that seed from 
 smooth ears yielded better than seed from rough ones. None of these 
 investigators reported differences in pericarp injuries between the two 
 ear types, but the excellent pictures published by Holbert ct al. in 1924 
 (11, Figs. 65-70) clearly show numerous kernels in rough ears with 
 the pericarp severely damaged at the crown. 
 
 In 1930, Koehler and Holbert (29) pointed out that rough ears are 
 particularly subject to pericarp breakage, and that pericarp injuries 
 and broken tip caps facilitate seed infection by soil organisms. Subse- j 
 quent experiments by the writer in 1933-1936 revealed that differences ; 
 in field performance between rough and smooth ears were probably 
 due mainly, but not entirely, to differences in the condition of the 
 pericarp. 
 
 A project on the pathological significance of pericarp injuries in 
 seed corn was begun by the writer in 1933. Research on this problem 
 and the types of soil organism involved had been very limited up to 
 that time. Brief reports were published in 1935 (26, 27), 1936 (22), 
 1938 (30), 1948 (23), and 1954 (28). Published results by other 
 investigators are mentioned throughout this bulletin where they apply 
 to the experiments reported. 
 
1957} 
 
 Pericarp Injuries in Seed Corn 
 
 GENERAL MATERIALS AND METHODS 
 
 Seed samples 
 
 Most commercial samples of seed used in determining the fre- 
 quency and types of pericarp injuries were obtained from the Illinois 
 Crop Improvement Association. Some were also taken from remnants 
 of seed used in the Illinois Station's annual tests of commercial hybrids. 
 Seed of inbreds and single crosses for studying resistance in relation to 
 pericarp injury were supplied by the Plant Breeding Division of the 
 Agronomy Department and by the Illinois Seed Producers Association. 
 
 For some experiments it was desired to have seed from open- 
 pedigree hybrids, free of pericarp damage. Arrangements with various 
 producers permitted the writer to pick the ears by hand directly from 
 a seed-production field. These ears were rack-dried and handled care- 
 fully at all times to prevent pericarp damage. 
 
 Injury classes. Eight classes of pericarp injury were usually 
 recognized: 
 
 1. Severe crown injury — one-fourth or more of the crown peri- 
 carp missing. 
 
 2. Slight crown injury — crown pericarp cracked or less than one- 
 fourth missing. 
 
 3. Injury over the plumule — any break on the face of the germ 
 area above the central node and not limited to the edge of the germ 
 
 Pericarp injury over the plumule caused by mechanical operations. (Fig. 1) 
 
Bulletin No. h\7 
 
 [September, 
 
 Pericarp injury over the radicle. Note that on two kernels the injury ex- 
 tends to the lower margin of the germ area. Such injuries were classified 
 as injuries over the radicle, rather than injury at the margin of the germ. 
 
 (Fig. 2) 
 
 area (Fig. 1). (The central node often appears slightly elevated in the 
 center of the germ area as shown in Fig. 2.) 
 
 4. Injury over the radicle — injuries below the central node, in- 
 cluding the lowest margin of the germ area (Fig. 2). 
 
 Pericarp injury at the margin of the germ area. These, as other injury 
 classes, varied in size, sometimes consisting of a small crack, as is shown 
 on the right. (Fig. 3) 
 
1957 
 
 Pericarp Injuries in Seed Corn 
 
 5. Injury around the edge of the germ — injury anywhere on the 
 entire periphery of the germ area except the lowest part directly over 
 the radicle (Fig. 3). 
 
 6. Other pericarp injuries — injuries on the side or back of the 
 kernels, including cracks which often occur when the kernels are 
 wrinkled near the tip. Some kernels showed deep fractures extending 
 through the horny endosperm. 
 
 Other pericarp injuries. This category included all pericarp injuries not 
 specifically named in other classes. They occurred primarily on the edges 
 and backs of the kernels and frequently involved the exposure of only 
 horny endosperm. (Fig. 4) 
 
 Tip cap broken off is not, strictly speaking, a pericarp injury, but 
 it is included because it is related and predisposes the seed to invasion 
 by soil fungi. Cracked kernels were recorded only in the data presented 
 in Table 5. Such kernels were rare in commercial seed samples, and 
 therefore this classification was not ordinarily used in examining them. 
 
 Examination and sorting. A group of specimens for each injury 
 class was prepared for the guidance of assistants who did the sorting. 
 Until 1951 seeds were examined with a 9x binocular microscope or a 
 7x tripod magnifying glass. In that year, however, a staining technique 
 was adapted, similar to one used by Huelsen and Brown (21), which 
 made it possible to detect more than twice as many injuries of most 
 
M Bulletin No. 617 [September, 
 
 classes. Subsequently all seeds were stained by the following procedure 
 before examination, and a magnifier was used only for questionable 
 cases. 
 
 A sample of 200 kernels in a wide-mouthed bottle was covered with 
 a 0.1 -percent solution of Fast Green FCF in water and stirred inter- 
 mittently for 30 seconds. The seed was then washed in several changes 
 of water and spread on absorbent paper to air dry. 
 
 The stain adhered only to the broken places in the pericarp and to 
 the tip where the kernel had been attached to the pedicel. It was de- 
 termined that this stain had no biological effect, so the seed could be 
 planted for seedling-blight comparison tests. 
 
 Each injury was recorded, and as kernels frequently had more than 
 one type, the total injuries in a sample sometimes exceeded 100 percent. 
 For this reason the percent of sound kernels is also given in the tables. 
 
 For some experiments certain types of injury were made by cutting 
 off or into the pericarp with a sharp knife. When removing a part of 
 the pericarp, an effort was made to remove as little as possible of the 
 underlying tissue. 
 
 Pretesting for fungicide or infection. Untreated seed was de- 
 sired for some tests. Until 1951 commercial samples of seed for those 
 tests were tested for the presence of a seed-treating fungicide. But 
 after the staining technique was adopted, this testing was discontinued 
 because originally treated and untreated seed showed no appreciable 
 difference in results in the cold tests. Evidently so little fungicidal 
 residue remained on the seed after staining and washing, that it was 
 ineffective. 
 
 When sound seed that had not been exposed to mechanical damage 
 was needed, hand-picked ears were tested for germination in a disin- 
 fested sand bench at 70°-75° F. Ears having 100-percent strong ger- 
 mination in a test of 10 representative kernels were then retested by 
 surface-sterilizing representative kernels and plating them on potato 
 dextrose agar medium to eliminate seed of ears with internal fungus 
 infections. Selected ears were then shelled (by hand, unless otherwise 
 noted). The seed was soaked with agitation for 10 minutes in a 0.28- 
 percent solution of sodium hypochlorite to eliminate the possibility of 
 infection from surface-borne organisms after planting. 
 
 Seed treatment. A protective fungicide was applied to the seed 
 for some tests. Unless otherwise mentioned, the chemical used was 
 thiram under the trade name, Arasan SF-X. The various rates of appli- 
 cation are given in the appropriate tables. 
 
1957] Pericarp Injuries in Seed Corn 1 1 
 
 Greenhouse and cold tests 
 
 Seedling-blight comparison tests at controlled temperatures were 
 made in a walk-in refrigerator and a greenhouse usually kept at 70°- 
 75° F. In the "cold tests," the trays were kept at 50° F. for a period of 
 5 to 20 days before placing them in the greenhouse. Seeds were planted 
 in wooden trays 3J/2 inches high that had been filled with 134 inches of 
 soil, then covered with an additional 1 1/4 inches of soil. Four or more 
 replications of thirty seeds each were used in each experiment. The 
 trays were stacked to avoid water loss during the cold period. Except 
 for experiments where specific soil moistures were desired, the moisture 
 content of the soil was adjusted to the damp margin of its favorable 
 working range and no additional moisture was added until the trays 
 were removed to the greenhouse. 
 
 For experiments with naturally infested soil, dark silt loam prairie 
 soil was taken from a field that had just previously been cropped to 
 corn. Hooker (12) found seedling-blight damage most pronounced in 
 soil that had previously been planted to oats or corn, least when it had 
 been meadow. However he found considerable variation between sam- 
 ples from two farms with similar rotations. Soils used in the cold tests 
 varied in their ability to infect the seed, but some control could be 
 exercised over the severity of the disease by varying the length of time 
 in the refrigerated chamber. Some soils required a day or two longer 
 than others. 
 
 For inoculation with pure cultures, plantings were made in Torpedo 
 sand (coarse builder's sand) that had been steam-sterilized or treated 
 with formaldehyde. Results were similar to those obtained with soil, 
 but sand was preferable for these plantings as steam-sterilized soil was 
 usually toxic to seedlings. 
 
 Results in the cold tests were recorded by several methods. Data 
 were taken after the third leaf was well-developed in the check rows 
 -the rows most nearly free from disease — and before the fourth 
 leaf emerged. Stand was recorded and vigor estimated by one of the 
 following measures: (a) height of seedlings above ground to the tallest 
 leaf, (b) green weight of seedlings per replicate, and (c) growth index, 
 derived by giving a value of 4 for a plant with 3 leaves, 3 for 2 leaves, 
 2 for 1 leaf, and 1 for a coleoptile that had emerged but not opened to 
 expose the first leaf (Fig. 14). Totals were then adjusted to give a 
 value of 100 for a perfect stand of plants with 3 leaves. Comparative 
 values for these three methods are given in Fig. 11. 
 
12 Bulletin No. 617 [September, 
 
 Field tests 
 
 All field tests were made on the Agronomy South Farm at Urbana. 
 Soil was a dark silt loam prairie soil of good, but not exceptional, fer- 
 tility in a rotation that included a legume one year in four. Plots were 
 usually 2 X 10 hills in size, spaced 39.6 inches (4,000 hills per acre) 
 with 3 kernels per hill. Replications varied from 8 to 12, depending on 
 the experiment. The time of planting was consistent with the usual 
 agricultural practice in the area. Yield as well as stand data were 
 obtained. 
 
 Statistical interpretation 
 
 The significance of results was measured by the analysis of vari- 
 ance. Unless otherwise indicated, the least significant difference 
 (L.S.D.) given in the tables is based on the 5-percent level. Where a 
 more precise interpretation seemed advisable, percentage figures were 
 converted to angles (arc sin times square root of the percentage), a 
 figure of 90 being equivalent to 100 percent. However, the figures for 
 angles and percents are not related by a linear function, as can be seen 
 in Tables 14, 17, and 20. Correlation coefficients were calculated for 
 some data. 
 
 OCCURRENCE OF PERICARP INJURIES 
 
 Prevalence of injuries in commercial seed 
 
 Commercial samples of seed corn were examined and separated 
 into seven injury classes, beginning with the 1942 crop. Seeds were 
 examined with magnifiers until after 1951 when the staining technique 
 described on page 10 was used for examinations. In 1951 samples were 
 examined before and after staining and a considerable number of in- 
 juries were detected that had not been noticeable before staining (Table 
 1). Samples were reduced to size with a Boerner divider and 200 
 kernels were used for each analysis. The number of samples varied 
 from year to year, as is shown in Table 1. 
 
 Yearly variations. Two classes of pericarp injuries — severe 
 crown injury and tip cap broken off — -offered a good index of com- 
 parison for the entire period since they are easy to detect and had been 
 revealed in the same percentages both stained and unstained (1951, 
 Table 1). Severe crown injury varied from 1.5 percent in 1945 to 8.3 
 percent in 1952. Tip cap broken off varied from 2.8 percent in 1947 to 
 12.6 percent in 1943. Part of this variation may be accounted for by the 
 
Pericarp Injuries in Seed Corn 
 
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1957] Pericarp Injuries in Seed Corn 15 
 
 small number of samples analyzed, but the range of difference indicates 
 that the occurrence of pericarp injuries may vary widely from year to 
 year. 
 
 Variations between samples were found in each year that seed 
 was examined for injuries. This agrees with the results of Tatum (43) 
 who noted that ". . . the type and degree of injury vary with the differ- 
 ent producers. Some consistently produce seed that is relatively free 
 from injury while others rather consistently injure a high percent of 
 the kernels." Average percentages of sound and damaged kernels for 
 the 10 best and 10 poorest samples are given for the last four years of 
 data in Table 1. In 1952, the 10 best samples had 2.9 percent of the 
 kernels injured at the crown; the 10 poorest had 17.6 percent. That 
 there are such wide differences suggests that much improvement over 
 present methods of processing seed is possible. 
 
 Variations between grades. Samples of six selected grade sizes 
 of the same hybrid were obtained from each of a number of seed 
 processors for three years. There was a strong trend for the percentage 
 of crown injury (severe and slight) to increase as the size of kernel 
 increased. This type of injury also occurred more frequently in flats 
 than in rounds. Injury over the plumule in 1953 also increased signifi- 
 cantly as size of kernel increased, but rounds had more injuries of this 
 type than flats. The same relationship held for tip cap broken off, with 
 significant differences in two years (Table 2). Sound kernels, as might 
 be expected, increased as size of kernels decreased, significantly so in 
 one year. In two years there were more sound kernels among the flats 
 than among the rounds, and this was significant in one year. The re- 
 sults of this three-year test, representing 14 growers in 1953, agree 
 with more limited data reported by Wortman and Rinke (46) ; that is, 
 the most crown injury occurred in flats; the most injury on the face of 
 the germ in rounds; and the most total injury in rounds. 
 
 Effect of maturity and hybrid 
 
 Spontaneous pericarp injuries. Three double crosses were tested 
 
 in 1955 for spontaneous cracking of the pericarp in relation to maturity 
 
 and hybrid. These were made up by using seed of inbreds Ind. WF9 
 
 male sterile crossed with C.I. 187-2, Ind. 38-11, and Conn. C103, 
 
 [ respectively, as the ear parents and J a. L317 x 111. Hy2 as the pollen 
 
 j parent. As the pericarp consists entirely of maternal tissue, the pollin- 
 
 i ator probably had no effect on the results. Each replication represented 
 
 five or more ears and a 200-kernel sample was taken from each of six 
 
 replications. 
 
10 
 
 Bulletin No. 617 
 
 [September, 
 
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18 Bulletin No. 617 [September, 
 
 Ears were harvested at four stages of maturity and dried in racks 
 at room temperature or by forced air at 105° F., but the method of 
 drying apparently made no difference in the amount of spontaneous 
 cracking. Ears were carefully shelled by hand to avoid mechanical 
 pericarp injuries. 
 
 All hybrids showed highly significant differences in the percent of 
 sound kernels at different stages of maturity (Table 3). On immature 
 seed, the pericarp became wrinkled and cracks developed in the part of 
 the kernel near the tip end; this usually occurred on the back of the 
 kernel where it was classified as "other pericarp injuries." Differences 
 in spontaneous cracking in this class, due to differences in maturity, 
 also were highly significant for all hybrids. Greater differences had 
 been observed in a previous experiment (28). Some spontaneous cracks 
 also appeared over the radicle. Most of the cracks could not be seen 
 without staining. Differences in the occurrence of spontaneous pericarp 
 injury were greater at different stages of maturity than between hy- 
 brids. In the predent stage at an average grain moisture of 61 percent, 
 spontaneous cracking was especially noticeable; it became negligible by 
 the time 99 percent of the kernels were dented (Table 3). 
 
 Mechanical injuries. The same hybrids were used in another; 
 experiment to determine the effect of maturity and hybrid on mechan- 
 ical damage. Four replications, consisting of a group of ears from each: 
 hybrid at each stage of maturity, were air dried to about 10-percent \ 
 moisture and shelled by hand. The seed was then dropped 15 feet onto 
 a smooth stone floor. 
 
 In this experiment differences between hybrids were as striking as; 
 differences due to stage of maturity (Table 4). For each hybrid, ma-( 
 ture seed had the highest percent of sound kernels and the lowest 
 percent of injuries around the edge of the germ and "other pericarp; 
 injuries." Differences between mature and immature seed for these two 
 pericarp injury classes were usually highly significant (Table 4). The 
 hybrid that had the lowest percentage of sound kernels also had the 
 highest incidence of injured kernels within most of the injury classes 
 (Table 4, summary for hybrids). 
 
 Effect of mechanical shelling 
 
 Type of sheller. Hybrid U.S. 13 was used in 1953 and duplicate 
 lots were shelled with a 2-hole sheller and with a cylinder sheller. 
 When ears were shelled with the 2-hole sheller, sound kernels averaged 
 62.9 percent, while with the cylinder sheller. the percentage — 50.7 — 
 was significantly less (Table 5). More pericarp damage was caused by 
 
1957 
 
 Pericarp Injuries in Seed Corn 
 
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1957] Pericarp Injuries in Seed Corn 21 
 
 the cylinder shelter than by the 2-hole machine, especially crown in- 
 juries, injuries around the margin of the germ, and "other pericarp 
 injuries." These differences also were significant (Table 5). The cylin- 
 der sheller w r as operated in the manner and at the speed determined at 
 the factory. Changes could probably have been made to markedly re- 
 duce the pericarp damage. 
 
 Grain moisture at shelling. Hybrid 111. 972-A1 was shelled with 
 a power 2-hole sheller in 1948. Ears shelled at high moisture were 
 harvested at the desired moisture condition. Those shelled at low mois- 
 ture were dried at about 105° F. with forced air to the desired moisture. 
 After shelling, seed with over 12-percent moisture was dried to 12 
 percent. All samples were passed through a small motor-driven grader 
 and a Boerner divider was used to obtain several 200-kernel samples 
 from the medium and large flats. 
 
 The highest percentage of sound kernels of 111. 972-A1 occurred 
 when the seed was shelled at 5 to 16.7 percent moisture. Differences 
 were not significant through that range. But from 16.7 percent, sound 
 kernels began to decrease sharply with increases in moisture (Table 6, 
 Fig. 5). Correlation coefficients show a highly significant positive cor- 
 relation between grain moisture and number of pericarp injuries for all 
 injury classes except slight crown injury (Table 6). 
 
 Similar results were obtained w r ith U.S. 13. In this experiment, 
 two types of shellers were used. The highest percentage of sound 
 kernels occurred at about 12-percent moisture with both kinds of 
 shellers (Table 5, Fig. 5). There was a significant decrease in the 
 number of sound kernels at lower or higher moistures. With few ex- 
 ceptions, the various kinds of injury were most numerous at the highest 
 moisture and least near 12 percent. Severe crown injury, injury over 
 the plumule, other pericarp injuries, and tip cap broken off had the 
 closest correlations with moisture at shelling time. 
 
 Tatum and Zuber (44) reported data for shelling at only two grain 
 moistures. They reported about twice as much kernel injury at 7.6 
 percent as at 12.0 percent. Considering data from the tests reported 
 here, it appears that the least total pericarp damage occurs when corn 
 is shelled at about 12 percent moisture and the least of the two most 
 damaging types of injury occurs at about 10 percent moisture (Fig. 5). 
 
 Huelsen and Brown (21) found a much higher moisture to be 
 favorable for shelling sweet corn; the best grain quality was assured 
 when the corn was shelled at 20 to 25 percent. 
 
22 
 
 Bulletin Xo. 617 
 
 [September 
 
 100 
 
 SEED WITH SOUND PERICARPS 
 
 2-HOLE SHELLER, ILL 972-A 
 2-HOLE SHELLER, U.S- 13 
 CYLINDER SHELLER, U.S. 13 
 
 2 
 
 INJURIES OVER THE PLUMULE 
 + SEVERE CROWN INJURIES 
 
 10 15 20 25 
 
 GRAIN MOISTURE WHEN SHELLED (PERCENT) 
 
 Effect of grain moisture at shelling. The percent of sound kernels decreased 
 while the percent of kernels with severe crown injury and injury over or 
 near the plumule — the most severe in their effects on seedling susceptibility 
 to blight — increased at high grain moistures. Two hybrids and two differ- 
 ent types of sheller were used. (Fig. 5) 
 
1957] Pericarp Injuries in Seed Corn 23 
 
 EFFECT OF PERICARP INJURIES ON SEEDLING GROWTH, 
 
 YIELD, AND RESISTANCE TO BLIGHT IN 
 
 NATURALLY INFESTED SOIL 
 
 The effects of various types of pericarp injury on seedling growth 
 were compared by the "cold test" method and in field tests on the 
 Agronomy South Farm. None of the seed used in these experiments 
 had been treated with a fungicide, unless specifically mentioned. A 
 literature review on cold testing has been published by Wernham (45). 
 
 Seed with unsorted pericarp injuries 
 
 Cold tests. Seed of hybrid U.S. 13 that had been shelled at vari- 
 ous grain moistures was tested for germination. All seed, whether hand- 
 shelled or machine-shelled, germinated well on Kimpack in a warm 
 germinator, but the results were quite different when the seed w r as 
 planted in naturally infested soil and kept at 50° F. for 10 days. Hand- 
 shelled seed, with 97.3 percent sound kernels, produced a stand of 90 
 percent, but the best stand from machine-shelled seed was 73.3 percent 
 (Table 7). Best stands and green weights from machine-shelled seed 
 were obtained when the seed was shelled at 6.8 to 12 percent moisture; 
 both stand and green weight decreased rapidly as the moisture at shell- 
 ing increased. 
 
 Field tests. Such differences as are mentioned above are, of 
 
 course, especially prone to show under adverse growing conditions as 
 
 occurred in the cold tests. Under average field conditions, there would 
 
 not usually be such marked differences between the performances of 
 
 sound and injured seed. However, in a three-year field test on the 
 
 ! Agronomy South Farm, when seed was not treated with a fungicide, 
 
 ! commercial seed produced stands of 84.1 percent, while the stand from 
 
 j. hand-handled seed was 93.6 percent (Table 8). Here again, the obvious 
 
 difference between the two seed lots was in pericarp condition. Com- 
 
 I mercial seed had an average of only 18.6 percent sound kernels, while 
 
 i hand-picked seed averaged 94 percent sound (Table 8). 
 
 Considerable differences in yield also occurred in the field tests. 
 ' Acre yields for commercial seed averaged 87.1 bushels, while hand- 
 shelled seed averaged 96.9 bushels. Such differences as were noted in 
 stand would not result in such differences in yield if stand were the 
 only factor affecting yield. But while there is a greater loss in stand 
 from pericarp-injured seed due to seedling blight from soil-borne infec- 
 I tion, there is also a reduction in the average vigor of plants when the 
 seed has been injured (28). 
 
24 Bulletin No. 617 [September, 
 
 Importance of type of injury 
 
 Cold tests. Commercial samples of seed were examined for peri- 
 carp injury and samples from each injury class (Table 1) were saved 
 for determining their relative susceptibilities to damage by seedling 
 blight. ( )nly kernels with one type of injury were used in these tests; 
 those with multiple injuries were discarded. Except for crown injury. 
 
 Table 7. — Effect of Shelling Method and Grain Moisture at Shelling 
 
 on Stand and Green Weight in Cold Tests 
 
 (Hybrid U.S. 13, 1953 crop, shelled at various grain moistures by hand and 
 
 and by two tvpes of mechanical sheller, and planted in naturally infested 
 
 soil, kept at 50° F. for 10 days and at 70° -75° F. for 11 days. Part of 
 
 the seed was treated with Arasan SF-X, ->4 ounce per bushel.) 
 
 Grain 
 
 Kernels 
 with sound 
 
 Stand 
 
 
 Green 
 
 weight b 
 
 moisture at 
 
 
 
 
 
 shelling 
 
 pericarps a 
 
 Untreated Treated 
 
 Untreated 
 
 Treated 
 
 perct. 
 
 perct. 
 
 perct. 
 
 
 grams 
 
 
 
 Hand-shelled 
 
 
 
 
 12.4 
 
 97.3 
 
 90.0 
 2-hole sheller 
 
 97.5 
 
 55.9 
 
 60.4 
 
 29.4 
 
 39.8 
 
 22.8 
 
 43.3 
 
 10.3 
 
 19.9 
 
 24.6 
 
 45.7 
 
 27.8 
 
 49.4 
 
 14.2 
 
 23.6 
 
 21.0 
 
 54.5 
 
 32.8 
 
 54.4 
 
 17.0 
 
 25.8 
 
 17.4 
 
 61.6 
 
 41.7 
 
 61.1 
 
 22.1 
 
 31.2 
 
 14.3 
 
 72.4 
 
 63.3 
 
 78.9 
 
 36.6 
 
 45.4 
 
 11.9 
 
 82.3 
 
 73.3 
 
 86.7 
 
 43.7 
 
 49.4 
 
 9.9 
 
 75.9 
 
 72.2 
 
 86.1 
 
 43.7 
 
 49.0 
 
 6.8 
 
 71.1 
 
 71.7 
 
 88.9 
 
 42.4 
 
 51.7 
 
 Average 62.9 50.7 68.6 28.8 37.0 
 
 Cylinder sheller 
 
 29.4 
 
 33.0 
 
 16.1 
 
 36.7 
 
 7.7 
 
 15.6 
 
 24.6 
 
 39.1 
 
 24.4 
 
 37.8 
 
 11.7 
 
 17.1 
 
 21.0 
 
 49.8 
 
 25.6 
 
 50.0 
 
 13.7 
 
 23.1 
 
 17.4 
 
 55.5 
 
 30.6 
 
 52.8 
 
 15.9 
 
 26.0 
 
 14.3 
 
 57.8 
 
 47.7 
 
 61.1 
 
 27.0 
 
 33.0 
 
 11.9 
 
 63.0 
 
 60.0 
 
 75.0 
 
 35.1 
 
 44.9 
 
 9.9 
 
 55.4 
 
 65.0 
 
 78.3 
 
 38.1 
 
 44.7 
 
 6.8 
 
 52.5 
 
 53.9 
 
 79.4 
 
 36.9 
 
 46.3 
 
 Average 
 
 50.7 
 
 40.4 
 
 58.9 
 
 23.3 
 
 31.3 
 
 L.S.D. (5-perceni 
 
 
 
 
 
 
 level) for 
 
 
 
 
 
 
 moisture 
 
 3.5 
 
 9.3 
 
 7.2 
 
 5.S 
 
 5.9 
 
 L.S.D. (5-percent 
 
 
 
 
 
 level) for 
 
 
 
 
 
 
 sheller 
 
 1.3 
 
 2.6 
 
 3. 1 
 
 1. 7 
 
 1 .9 
 
 : ' The distribution of the various types of pericarp injury is given in Table 5. 
 b Green weight of plants from 100 seeds planted. 
 
195'/ 
 
 Pericarp Injuries in Seed Corn 
 
 25 
 
 which was divided into "severe" and "slight," each injury class repre- 
 sented, as nearly as possible, a random sample regardless of the extent 
 of injury. One replication of one test is shown in Fig. 6. In the cold 
 tests, the most severe seedling blight occurred when the seed had se- 
 vere crown injuries. Slight crown injury was important in this respect, 
 but not to as great an extent. The green weight per plant was reduced 
 more with both types of crown injury than with any other type of 
 pericarp damage (Table 9). Stands were greatly reduced when the 
 injury was over the plumule, but the plants that survived had fairly 
 good vigor. This effect was consistent for the various years. The results 
 
 Table 8. — Effect of Pericarp Injuries on Stand and Yield in Field Tests 
 With and Without Seed Treatment 
 
 (Three-year average of Hybrids U.S. 13 and 111. 972-A1, seed treated 
 with several protective fungicides at various rates* -1 ) 
 
 Seed treatment 
 
 Commercial seed b 
 
 Hand-in- 
 
 ured seed b 
 
 Hand-handled seed 1 ' 
 
 
 Rate 
 
 Stand 
 
 Increase 
 
 Stand 
 
 Increase 
 
 Stand 
 
 Increase 
 
 Fungicide 
 
 oz. per 
 
 and 
 
 over 
 
 and 
 
 over 
 
 and 
 
 over 
 
 
 bu.) 
 
 yield 
 
 check 
 
 yield 
 
 check 
 
 yield 
 
 check 
 
 
 
 
 Stand (p 
 
 ercent) 
 
 
 
 
 None (check) 
 
 
 84.1 
 
 
 80.9 
 
 
 93.6 
 
 
 Arasan SF a 
 
 Y A 
 
 91.6 
 
 7 '.5** 
 
 92.2 
 
 11.3** 
 
 94.9 
 
 V.3 
 
 
 1 
 
 92.0 
 
 7.9** 
 
 93.8 
 
 12.9** 
 
 95.1 
 
 1.5 
 
 Spergon 
 
 
 
 
 
 
 
 
 DDT-SL a 
 
 Vi 
 
 89.0 
 
 4.9* 
 
 87.7 
 
 6.8** 
 
 93.9 
 
 0.3 
 
 
 1 
 
 89.6 
 
 5.5** 
 
 89.7 
 
 8.8** 
 
 94.3 
 
 0.7 
 
 Phygon a 
 
 V* 
 
 89.8 
 
 5.7** 
 
 92.0 
 
 11.1** 
 
 94.0 
 
 0.4 
 
 Average for 
 
 
 
 
 
 
 
 
 treatments 
 
 
 90.4 
 
 6.3** 
 
 91.1 
 
 10.2** 
 
 94.4 
 
 0.8 
 
 
 
 
 Yield (bushels) 
 
 
 
 
 None (check) 
 
 
 87.1 
 
 
 84.7 
 
 
 96.9 
 
 
 Arasan SF 
 
 l A 
 
 94.3 
 
 y 2** 
 
 94.8 
 
 io!i** 
 
 97.7 
 
 0.8 
 
 
 l 
 
 95.9 
 
 8^8** 
 
 96.3 
 
 11.6** 
 
 97.6 
 
 0.7 
 
 Spergon 
 
 
 
 
 
 
 
 
 DDT-SL 
 
 V2 
 
 93.1 
 
 6.0** 
 
 92.3 
 
 7.6** 
 
 96.6 
 
 -0.3 
 
 
 1 
 
 93.7 
 
 6.6** 
 
 94.1 
 
 9.4** 
 
 98.2 
 
 1.3 
 
 Phygon 
 
 V* 
 
 94.0 
 
 6.9** 
 
 93.2 
 
 8.5** 
 
 96.2 
 
 -0.7 
 
 Average for 
 
 
 
 
 
 
 
 
 treatments 
 
 
 94.2 
 
 7.1** 
 
 94.1 
 
 9.4** 
 
 97.3 
 
 0.4 
 
 :l Arasan SF, active ingredient 75 percent thiram; Spergon DDT-SL, active ingredient 
 92 percent chloranil plus 3 percent DDT; and Phygon XL-DDT, active ingredient 50 percent 
 2,3-dichloro-l,4-napthoquinone plus 3 percent DDT. 
 
 b Commercially processed seed contained kernels with various types of pericarp injuries, 
 18.6 percent sound kernels. Hand-injured seed had been handpicked; all were cut with a 
 knife to injure the crown pericarp. Hand-handled seed had been carefully picked and handled 
 to avoid any injuries, and had 94 percent sound kernels. 
 
 * Significant at the 5-percent level. 
 ** Significant at the 1-percent level. 
 
26 
 
 Bulletin No. 017 
 
 September, 
 
 Sound 
 
 Severe 
 
 Slight 
 
 Injury 
 
 1 n j u ry 
 
 Tip cap 
 
 Injury 
 
 Other 
 
 check 
 
 crown 
 
 crown 
 
 of edge 
 
 over 
 
 broken 
 
 over 
 
 pericarp 
 
 
 injury 
 
 injury 
 
 of germ 
 
 radicle 
 
 off 
 
 plumule 
 
 injuries 
 
 Differences in stand and vigor caused by seedling blight in a cold test with 
 sound and pericarp-injured seed. All kernels were sorted from commercial 
 seed samples. (Fig. 6) 
 
 of six crop years of cold tests are shown in Table 9, with the injury 
 classes arranged in the order of their average importance. Both stand 
 and green weight were significantly reduced for seed with all types of 
 injury, including broken tip caps, as compared with sound seed. 
 
 One surprising result in this series of tests was the superior per- 
 formance of hand-handled seed over healthy-appearing seed with 
 sound pericarps sorted from commercial samples. The average stand 
 for commercial sound seed was 88.5 percent; the hand-handled seed of 
 U.S. 13 in 1953 produced a stand of 94.6 percent (Table 9). It is 
 unlikely that the commercial seed sorted as "sound" had undetected 
 injuries, as the samples were stained before sorting. This may lend 
 support to Livingston's conclusion (33) that artificial drying in itself 
 has a damaging effect on the vitality of seedlings and their resistance to 
 blight. 
 
 Field tests. Yield comparisons w r ere made from data ©btained in 
 the Agricultural Experiment Station's hybrid corn test in 1954 (38). 
 This test was selected for study because differences in stands between 
 
 
1957] Pericarp Injuries in Seed Corn 27 
 
 Table 9. — Effect of Type of Pericarp Injury on Stand 
 and Green Weight in Cold Tests 
 
 (Seed of commercial hybrids, 6 crop years, and of U.S. 13, 1952 crop planted 
 
 in naturally infested soil at 50° F. for 10 days, then placed 
 
 in a greenhouse at 70°-75° F.) 
 
 Average, Hybrid U.S. 13, 1952 
 
 many 
 
 Pericarp hybrids, Green Preen 
 
 condition 1944-1953 <z*. n „A weight from „-„u*. ™,- 
 
 Stand 100 seeds weig £* t per 
 
 Stand planted P 
 
 perct. perct. grams grams 
 
 Mechanically processed seed 
 
 Severe crown injury 17.4 2.7 .5 .185 
 
 Injury over plumule 24.2 14.7 9.4 .639 
 
 Slight crown injury 36.2 26.0 8.4 .323 
 
 Injury at margin of germ area 36.0 27.3 13.7 .502 
 
 Other pericarp injuries 44.8 34.0 17.9 .526 
 
 Injury over radicle 44.9 32.0 19.9 .622 
 
 Tip cap broken off 61.1 48.7 29.2 .600 
 
 Sound 88.5 74.7 48.1 .644 
 
 Hand-handled seed 
 
 Sound 94.6 71.4 .755 
 
 L.S.D. (5-percent level). .. 9.1 10.2 6.5 .079 
 
 hybrids appeared to be the result of seedling blight, although all seed 
 had been treated before planting with a protective fungicide. Reduc- 
 tions in stand and yield were both highly correlated with severe crown 
 injury (Table 10). When crown injury was slight the correlation was 
 still significant at the 5-percent level. Injury near plumule showed a 
 higher negative correlation with stand than with yield. This field test 
 supports the conclusions derived from the cold tests: that while peri- 
 carp injury at the crown and over the plumule both contribute to severe 
 losses in stand from seedling blight, the plants that survive have the 
 poorest vigor when the seed pericarp has been injured at the crown. 
 
 Data from the 1955 commercial hybrid tests showed highly signifi- 
 cant correlations between stand and yield in two of the five tests in Illi- 
 nois (32). The results of the Carbondale test, which were studied for 
 relationships between stand, yield, and pericarp condition, showed cor- 
 relations similar to those noted in 1954. However, negative correlations 
 with stand and yield were significant only for severe crown injury and 
 "other pericarp injuries." 
 
28 
 
 Bulletin No. 617 
 
 [September, 
 
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1957 
 
 Pericarp Injuries in Seed Corn 
 
 29 
 
 
 Striped leaves such as these occurred on some plants in field plots in several 
 years, but only where pericarp-injured seed had been planted. (Fig. 7) 
 
 Plants with striped leaves (Fig. 7) were observed in Held plots 
 in 1937 and particularly in 1939. They occurred in all replicates planted 
 with seed that had the pericarp partially removed from the crown, but 
 did not appear in plots planted with sound seed. In the 1939 field exper- 
 iment, average percentages of striped plants were as follows: Station 
 strain of Reid Yellow Dent, 10.8; hybrid 111. 960. 3.2; and hybrid U.S. 
 13, 5.7 percent. In the young plant stage, the striped plants did not 
 average more than one-half the height of nonstriped ones. After the 
 plants had attained all their leaves, the upper leaves were observed to 
 be free from striping, especially those above the ear shoot. The plants 
 could not be removed for attempts at isolating fungi, because the test 
 had been planted for yield determinations. However, C. M. Wood worth 
 of the Illinois Station selfed a number of the most vigorous striped 
 plants and obtained some seed, which was planted the next year. No 
 striped plants appeared. Thus it seems clear that this striping was not 
 of a heritable nature and must have been a disease symptom. 
 
 Some virescent plants have been observed in field tests. When cold 
 
30 
 
 Bulletin Xo. 617 
 
 September, 
 
 tests were conducted with Aspergillus fiarus and A. tamarii inocula- 
 tions, virescence occurred among plants from pericarp-injured seed. 
 This effect is discussed further on pages 46 and 47. 
 
 Yield comparisons for similar stands 
 
 Field plots were planted with untreated sound and injured seed to 
 compare yield when stands were the same. Seed with sound pericarps 
 from hand-handled seed was planted at the rates of 2 and 3 kernels 
 per hill. Seed from the same ears with part of the crown pericarp 
 removed was planted at the rates of 3 and 4 kernels per hill. 
 
 Actual stands obtained, as a seven-year average, for seed with sound 
 pericarps planted at 2 kernels per hill were 1.88 plants per hill, at 
 
 3 kernels per hill, 2.83; for seed injured at the crown, stands were 2.33 
 plants per hill when planted at 3 kernels per hill, and 3.11 plants at 
 
 4 kernels per hill. 
 
 Comparing acre yields with the actual stand obtained (Fig. 8), it 
 may be seen that there is a range within which theoretically identical 
 stands can be compared. There was an average calculated difference in 
 yield of 16.5 bushels between plants from sound seed and plants from 
 seed with the crown pericarp injured, when stands were identical. This 
 difference was significant at the 5-percent level. 
 
 90 
 
 ^ — ""seed with sound pericarps 
 
 80 
 
 ^ "~^^ 
 
 Ul 
 
 # ^— - — """ 
 
 
 o 
 
 L.S.D. AT 
 
 
 < 
 
 5% LEVEL 
 
 
 £70 
 
 _i 
 
 
 — • 
 
 UJ 
 
 I 
 
 SEED WITH PERICARPS INJURED AT CROWN 
 
 V) 
 
 m 
 
 60 
 
 J 
 
 r , 
 
 2 2.5 3 
 
 AVERAGE STAND- PLANTS PER HILL 
 
 Differences in yield from untreated seed with sound and injured pericarps. 
 Seed was planted at several rates so that yields from the same field stands 
 could be compared. (Fig. 8) 
 
1957] 
 
 Pericarp Injuries in Seed Coi 
 
 31 
 
 Effect of temperature on preemergence growth of sound and injured seed 
 Rows 1 and 3 pericarp partially removed from the crown; 2 and 4 sound 
 pericarp. Seed shown in rows 3 and 4 were treated with the protective 
 rungicide, Arasan, at the rate of 1 ounce per bushel. (Fig 9) 
 
32 
 
 Bulletin No. 017 
 
 [September, 
 
 Table 11. — Effect of Temperature, Pericarp Condition, and Seed 
 
 Treatment on Preemergence Growth and Pythium 
 
 Infection of Seedlings 
 
 (Hybrid U.S. 13, part sound and part with the pericarp partially removed 
 from the crown, planted in moist field soil and kept constantly at 50°, 60°, 
 or 70° F. Part of seed of both pericarp conditions was treated with Arasan.) 
 
 Tem- 
 pera- 
 
 Seed 
 treat- 
 ment 
 
 Days 
 after 
 
 Figure 9, 
 row 
 
 Pericarp 
 
 breakage 
 
 clue to 
 
 Radicle 
 visible 
 
 Plumule 
 visible 
 
 Pythium- 
 infected 
 
 ture 
 (°F.) 
 
 (oz. per 
 bu.) 
 
 planting 
 
 no. 
 
 growth of 
 germ 
 
 germ 
 area 
 
 
 
 
 
 perct. 
 
 perct. 
 
 perct. 
 
 perct. 
 
 
 
 Seed 
 
 with crown pericarp injured 
 
 
 
 50 
 
 None 
 
 2 
 
 
 
 
 
 
 
 
 
 
 
 
 3 
 
 
 
 
 
 
 
 
 10 
 
 
 
 4 
 
 
 
 
 
 
 
 
 57 
 
 
 
 6 
 
 
 21 
 
 
 
 
 
 73 
 
 
 
 7 
 
 A 
 
 27 
 
 9 
 
 
 
 93 
 
 
 
 9 
 
 
 52 
 
 15 
 
 
 
 100 
 
 
 
 12 
 
 B 
 
 64 
 
 24 
 
 6 
 
 100 
 
 
 
 17 
 
 C 
 
 58 
 
 21 
 
 3 
 
 100 
 
 
 1 
 
 7 
 
 A 
 
 73 
 
 49 
 
 
 
 
 
 
 
 12 
 
 B 
 
 100 
 
 100 
 
 27 
 
 
 
 
 
 17 
 
 C 
 
 100 
 
 100 
 
 91 
 
 20 
 
 60 
 
 None 
 
 2 
 
 
 12 
 
 6 
 
 
 
 3 
 
 
 
 3 
 
 
 79 
 
 49 
 
 
 
 23 
 
 
 
 4 
 
 
 97 
 
 94 
 
 6 
 
 67 
 
 
 
 5 
 
 
 100 
 
 100 
 
 70 
 
 93 
 
 
 
 6 
 
 
 100 
 
 100 
 
 94 
 
 100 
 
 
 
 7 
 
 D 
 
 100 
 
 100 
 
 100 
 
 100 
 
 
 1 
 
 5 
 
 
 100 
 
 100 
 
 61 
 
 
 
 
 
 6 
 
 
 100 
 
 100 
 
 100 
 
 3 
 
 
 
 7 
 
 D 
 
 100 
 
 100 
 
 100 
 
 3 
 
 70 
 
 None 
 
 1 
 
 
 3 
 
 3 
 
 
 
 
 
 
 
 2 
 
 
 100 
 
 100 
 
 
 
 30 
 
 
 
 3 
 
 
 100 
 
 100 
 
 100 
 
 97 
 
 
 
 4 
 
 E 
 
 100 
 
 100 
 
 100 
 
 100 
 
 
 
 5 
 
 
 100 
 
 100 
 
 100 
 
 100 
 
 
 1 
 
 3 
 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 4 
 
 E 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 5 
 
 
 100 
 
 100 
 
 100 
 
 10 
 
 
 
 Seed with 
 
 sound pericarps 
 
 
 
 50 
 
 None 
 
 7 
 
 A 
 
 70 
 
 49 
 
 
 
 
 
 
 
 9 
 
 
 85 
 
 76 
 
 
 
 10 
 
 
 
 12 
 
 B 
 
 100 
 
 88 
 
 9 
 
 43 
 
 
 
 17 
 
 C 
 
 100 
 
 94 
 
 46 
 
 57 
 
 
 1 
 
 7 
 
 A 
 
 64 
 
 52 
 
 
 
 
 
 
 
 12 
 
 B 
 
 100 
 
 100 
 
 18 
 
 
 
 
 
 17 
 
 C 
 
 100 
 
 100 
 
 79 
 
 7 
 
 (Table is concluded on next page) 
 
1957 
 
 Pericarp Injuries in Seed Corn 
 Table 11. — Concluded 
 
 33 
 
 Tem- 
 pera- 
 
 Seed 
 treat- 
 ment 
 
 Days 
 
 after 
 
 Figure 9, 
 row 
 
 Pericarp 
 
 breakage 
 
 due to 
 
 Radicle 
 visible 
 
 Plumule 
 visible 
 
 Pythium- 
 infected 
 
 ture 
 
 (°F.) 
 
 (oz. per 
 bu.) 
 
 planting 
 
 no. 
 
 growth of 
 germ 
 
 germ 
 area 
 
 
 
 
 
 perct. 
 
 perct. 
 
 perct. 
 
 perct. 
 
 60 
 
 None 
 
 5 
 
 
 100 
 
 100 
 
 64 
 
 
 
 
 
 6 
 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 7 
 
 D 
 
 100 
 
 100 
 
 100 
 
 7 
 
 
 1 
 
 5 
 
 
 100 
 
 100 
 
 58 
 
 
 
 
 
 6 
 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 7 
 
 D 
 
 100 
 
 100 
 
 100 
 
 
 
 70 
 
 None 
 
 3 
 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 4 
 
 E 
 
 100 
 
 100 
 
 100 
 
 3 
 
 
 
 5 
 
 
 100 
 
 100 
 
 100 
 
 3 
 
 
 1 
 
 3 
 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 4 
 
 E 
 
 100 
 
 100 
 
 100 
 
 
 
 
 
 5 
 
 
 100 
 
 100 
 
 100 
 
 
 
 Effect of temperature 
 
 Preemergence growth at three temperatures. Good-quality seed 
 of U.S. 13, part of which had the pericarp partially removed from the 
 crown, was tested for preemergence growth in natural soil at three 
 temperatures. Only the data for the untreated samples will be con- 
 sidered here. 
 
 At 50° F. when the pericarp had been injured at the crown, ruptur- 
 ing of the pericarp over the germ due to swelling or growth began on 
 the fifth day and had reached 64 percent by the twelfth day, but none 
 of the plumules had emerged enough to be measurable (Table 11, Fig. 
 9). After 12 days at 50° F., no further growth took place, as all 
 embryos or seedlings had died from Pythium blight. Not even sound 
 seed emerged from the soil when kept constantly at 50° F. unless it had 
 been treated with a protective fungicide. This is approximately the 
 temperature at which the most damage from certain Pythium species 
 occurs. At lower temperatures — for example, 45° or 39° F. — others 
 (9, 18) have found seedling blight less severe. 
 
 At 60° F., pericarp breakage due to embryo growth began in crown- 
 injured seed in 2 days. Radicles were measurable in 4 days and plu- 
 mules in 5 days. Plumules did not start to emerge from the soil until 
 the tenth day. This temperature and pericarp condition was favorable 
 to Pythium invasion, which reached 100 percent on the sixth day in 
 
34 
 
 Bulletin No. 617 
 
 [September, 
 
 crown-injured seed (Table 11). As a result, the injured seed showed 
 retarded growth of plumules and radicles, compared with that of 
 sound seed. 
 
 At 70° 1\. a few pericarps had split open due to growth in one day 
 after planting. Radicles were measurable on the second day, plumules 
 on the third. At this temperature, although Pythium invasion was high 
 in injured seed within a few days, there was comparatively little differ- 
 ence in growth rate between injured and sound seed (Table 11, Fig. 9). 
 Seedlings emerged from the soil in 5 days. 
 
 Delayed exposure to cold. An experiment was conducted with 
 four hybrids to determine the effect of delaying exposure to cold after 
 planting. Part of the seed had the pericarp partially removed from the 
 crown. The trays were kept at 50° F. for 10 days in all cases, but as 
 more time elapsed between planting and exposure to cold, better stands 
 were obtained. Furthermore, the longer after planting the cold period 
 was delayed, the less difference there was in stands from sound and 
 from injured seed, due to the improved results from injured seed 
 (Table 12). 
 
 Thus it appears that resistance to seedling blight resulting from soil 
 
 Table 12. — Effect on Stand of Delaying Exposure of Sound and 
 Pericarp-Injured Seed to Cold After Planting 
 
 (Four hybrids planted in naturally infested soil and kept at 70° F. 
 up to 3 days before a 10-day period at 50° F.) 
 
 Pericarp condition 
 
 Days at Days at 
 
 70° F. 70° F. 
 
 before after 
 
 cold cold 
 
 period period 
 
 Stand (angles) 
 
 Hybrid 
 
 B 
 
 I) 
 
 Mean 
 
 Crown pericarp 
 
 
 
 
 
 
 
 
 partially removed 
 
 
 
 11 
 
 63 
 
 40 
 
 33 
 
 27 
 
 41 
 
 
 l a 
 
 10 
 
 61 
 
 60 
 
 54 
 
 46 
 
 55 
 
 
 2 b 
 
 9 
 
 77 
 
 80 
 
 72 
 
 70 
 
 75 
 
 
 3 C 
 
 8 
 
 87 
 
 80 
 
 82 
 
 65 
 
 78 
 
 Sound 
 
 
 
 11 
 
 82 
 
 77 
 
 78 
 
 47 
 
 71 
 
 
 1 
 
 10 
 
 87 
 
 74 
 
 87 
 
 70 
 
 80 
 
 
 2 
 
 9 
 
 83 
 
 87 
 
 87 
 
 85 
 
 86 
 
 L.S.D. (5-percent level), 
 
 3 
 
 8 
 
 90 
 
 87 
 
 90 
 
 87 
 
 89 
 
 both pericarp conditions 
 
 
 
 10 
 
 10 
 
 10 
 
 10 
 
 6 
 
 a No radicles or plumules had broken through the pericarp the first day. 
 b Radicles up to 0.4 inches long. Plumules had not broken through the pericarp. 
 G Radicles 0.4 to 2.5 inches long. Plumules 0.2 to 0.5 inches long. No emergence above 
 the soil. 
 
1957] 
 
 Pericarp Injuries in Seed Corn 
 
 35 
 
 Table 13. — Effect of Soil Moisture and Pericarp Condition on 
 Stand and Green Weight at Two Temperatures 
 
 (Hybrid U.S. 13, sound pericarps and two types of injury, planted in 
 
 naturally infested soil adjusted to three levels of moisture 3 
 
 and kept constantly at 60° or 70° F.) 
 
 Pericarp 
 
 Soil 
 moisture 
 
 Days after planting b 
 60° F. 70° F. 
 
 Stand 
 
 Green \ 
 60° F. 
 
 veight c 
 
 condition 
 
 60° F. 
 
 70° F. 
 
 70° F. 
 
 Pericarp injury 
 near plumule 
 
 Low 
 
 Medium 
 
 High 
 
 25 
 22 
 20 
 
 16 
 15 
 14 
 
 angle 
 73 88 
 53 82 
 34 68 
 
 gra 
 41 
 25 
 19 
 
 ms 
 48 
 44 
 39 
 
 Pericarp injured 
 at crown 
 
 Low 
 
 Medium 
 
 High 
 
 25 
 22 
 20 
 
 16 
 15 
 14 
 
 73 
 58 
 45 
 
 90 
 
 87 
 73 
 
 28 
 27 
 22 
 
 48 
 49 
 41 
 
 Sound 
 
 Low 
 
 Medium 
 
 High 
 
 25 
 22 
 20 
 
 16 
 15 
 14 
 
 86 
 87 
 85 
 
 88 
 90 
 
 87 
 
 64 
 66 
 67 
 
 60 
 63 
 69 
 
 L.S.D. (5-percent 1< 
 
 jvel) 
 
 
 
 12 
 
 11 
 
 10 
 
 9 
 
 a Soil was adjusted to 45 (low), 65 (medium), and 80 (high) percent of the moisture- 
 holding capacity, which was found to be about 40 percent based on dry weight, in the manner 
 in which it was used in this experiment. 
 
 b Data were recorded after sound seed reached the three-leaf stage. Plants from injured 
 seed were harvested at the same time, regardless of the number of leaves. 
 
 c Green weight of plants from 100 seeds planted. 
 
 infestation increases as germination becomes active, and the more days 
 germination can proceed in warm soil, the greater the resistance regard- 
 less of pericarp condition. 
 
 Effect of soil moisture 
 
 It has been shown that high soil moisture increases damage from 
 Pythium seedling blight (8), but previous reports have not mentioned 
 the effect of the pericarp condition. In this test it was desired to know 
 how moisture affects growth in infested soil when the pericarp condi- 
 tions of the seed differ. Injuries were made by shaving off part of the 
 crown pericarp and by making slight cuts to one side of the plumule 
 (Fig. 10A, page 39). Four replications of 25 seeds of one kind were 
 planted in naturally infested soil in 2-gallon cans and kept at 60° and 
 70° F. in apparatus known as the Wisconsin Soil Temperature Tanks 
 (25). The soil was adjusted to three levels of moisture: 45, 65, and 
 80 percent of the moisture-holding capacity. As used in this experi- 
 ment, the soil was found to have a water-holding capacity of about 40 
 percent based on dry weight. 
 
 At all three moisture levels, sound seed produced significantly better 
 green weights than seed with either type of pericarp injury (Table 13). 
 
36 Bulletin No. 617 [September, 
 
 1 )ifferences in stand due to differences in pericarp condition were signif- 
 icant only at 60° F. At both temperatures the rate of growth for sound 
 seed was faster as soil moisture increased, due to protection by the peri- 
 carp. But the opposite was true of plants grown from injured seed 
 i Table 13) ; where there was little protection from the pericarp, disease 
 damage increased greatly with increases in moisture. This was signifi- 
 cant at 70° F., but most outstanding at 60° F. There was little difference 
 in results between the two types of pericarp injury at the different soil 
 moistures. 
 
 EFFECT OF PERICARP INJURIES ON SEEDLING BLIGHT 
 CAUSED BY SPECIFIC FUNGI 
 
 Fungus isolations 
 
 Fungi were isolated from seed of hybrid U.S. 13 that had been 
 planted in moist, naturally infested soil. The ears had been hand-picked, 
 tested, and selected for freedom from internal infection, then surface- 
 disinfested with a solution of sodium hypochlorite. Part of the seed was 
 injured by removing part of the crown pericarp. After seed was re- 
 moved from the soil, it was cleaned with a soft toothbrush under run- 
 ning tap water. Radicles and plumules longer than 1/2 inch were 
 clipped, and seed was then washed and agitated under running water 
 for one hour. A small piece of tissue midway across the scutellum, 
 including a little of the central node of the embryo and a bit of the 
 endosperm, was removed asceptically and plated on plain water agar. 
 After two days a hyphal tip was isolated from each colony and manip- 
 ulated to free the isolates of bacteria. The original piece of tissue was 
 left in the Petri dish for several more days. 
 
 Pythium species were the first invaders of both sound and 
 crown-injured seed. Pythium was found in a small percentage of the 
 injured seeds two days after planting at 60° F., and in three days at 
 50° F. Isolations were not obtained from seed with sound pericarps 
 until the fourth day at 70° F., the seventh day at 60° F., and the 
 eighth day at 50° F. (Table 11). More than half of the Pythium iso- 
 lates were identified as P. debar yannm Hesse. Most of the remainder 
 could be classed as closely related or similar forms, one of which was 
 identified several times as P. ultimum Trow. P. idtimum appeared to 
 be the most common species causing seedling blight in some Wisconsin 
 soils (20). However, studies in Towa (10) showed P. debaryanum to 
 be the chief cause of seed decay and stunted growth of seedlings. 
 Sprague (42) also found it to be the most common of the sphaerospo- 
 
1957] Pericarp Injuries in Seed Corn 37 
 
 rangial species attacking Graminae in North Dakota and surrounding 
 regions. Many of the isolates could not be more closely identified be- 
 cause sporangia, oogonia, and antheridia — - all necessary for identifica- 
 tion — were not all obtained in culture. 
 
 Among these early isolations some pieces plated had bacteria as well 
 as Pythium, and some produced only bacteria. It seemed doubtful, how- 
 ever, that these bacteria were of much pathological significance. 
 
 Other fungi appeared rather frequently in tissue from crown- 
 injured seed plated six or more days after planting at 50° F., or 
 earlier at warmer temperatures. Among these were Penicillium species, 
 including P. oxalicum; Fusarium moniliforme; Trichoderma species; 
 Cephalosporium acremonium; Helminthosporium species; Sporodinia 
 species; Mucor species; and unidentified fungi. Some of these may 
 have been carried in or on the seed, although it had been tested and 
 selected for freedom from internal infection and disinfested with 
 sodium hypochlorite before planting. 
 
 Seed inoculation experiments 
 
 Comparisons between damage from blight in plants grown from 
 sound seed and those from seed with pericarp injuries were made by 
 inoculating seed of various pericarp conditions with each of the follow- 
 ing fungi: Pythium debaryanum Hesse, Penicillium oxalicum Currie 
 and Thorn, Aspergillus flavus Link, A. tamarii Kita, A. niger Van 
 Tieghem, Diplodia zeae (Schw.) Lev., Gibber ella zeac (Schw.) Petch, 
 Fusarium moniliforme Sheldon [G. fujikuroi (Saw.) Wr.], Tricho- 
 derma viride (Pers. ex Fries) Bisby, and miscellaneous Penicillium and 
 Aspergillus species. 
 
 Pythium debaryanum. The extent of seedling blight caused by 
 sphaerosporangial seed-rotting Pythium species is greatly influenced 
 by the condition of the pericarp. Whether this is also true for the 
 lobulate-sporangial forms, P. arrhenomanes and P. graminicola, has 
 not been determined and they rarely occurred in these isolations. That 
 this relationship is true of some Pythium species, then unidentified, 
 was previously reported by the writer (23). 
 
 A highly virulent strain of Pythium debaryanum was selected for 
 inoculation. A transplant was sent to T. C. Vanterpool, 1 a specialist in 
 Pythium taxonomy, who verified the writer's identification. Cultures 
 were grown on potato dextrose agar in 100 mm. Petri dishes. Four 
 cultures 4 to 5 days old were macerated with 200 ml. water in a Waring 
 
 1 Professor of Plant Pathology, University of Saskatchewan. 
 
38 
 
 Bulletin No. 617 
 
 [September, 
 
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1957] Pericarp Injuries in Seed Corn 39 
 
 Pericarp injuries made by hand. A. A slight cut alongside the plumule, as 
 used in experiments reported in Tables 13, 14, 15, and 20. B. Plumule ex- 
 posed, Table 17. C. Radicle exposed, Tables 14, 15, and 17. (Fig. 10) 
 
 Blendor for 15 to 20 seconds before covering the seed. The seed was 
 soaked for several minutes in the suspension with occasional stirring, 
 drained, then planted in disinfested Torpedo sand and natural soil. 
 
 The above-ground symptoms from Pythium inoculations were pri- 
 marily poor stands and weak plants, often pale in color, following 
 subjection to cold temperature, and weak plants lower in green weight 
 when grown at 70°-75° F. There were no specific foliage symptoms. 
 Similar observations were reported by Hoppe (17). 
 
 Relative susceptibility ratings for seed with various kinds of peri- 
 carp injury and different genetic constitution were very nearly the 
 same, regardless of whether they were inoculated and planted in disin- 
 fested sand or noninoculated and planted in naturally infested soil. 
 Inoculation had no additional effect on disease development in natural 
 soil. 
 
 Seed of U.S. 13 with various types of pericarp injury made by 
 hand was inoculated with a pure culture of Pythium debar yanum, 
 planted in disinfested sand, and kept at 50° F. for seven days before 
 placing in a warm greenhouse. (Fig. 10 shows a light cut along the 
 plumule and an exposed radicle.) Results in this test (Table 14) were 
 similar to those obtained with seed injured during commercial process- 
 ing planted in natural field soil (Table 9). In both sets of experiments, 
 green weights were reduced more by crown injuries, severe or slight, 
 than by any other type of pericarp damage (Tables 9 and 14). Injuries 
 
40 
 
 Bulletin No. 617 
 
 [Septentbt 
 
 CROWN PERICARP 
 PARTIALLY REMOVED 
 
 CUT SLIGHTLY 
 ALONGSIDE PLUMULE 
 
 INJURED AT EDGE 
 OF GERM AREA 
 
 PUNCTURED AT CROWN 
 
 HORNY ENDOSPERM 
 EXPOSED 
 
 RADICLE EXPOSED 
 
 TIP CAP 
 BROKEN OFF 
 
 CROWN PERICARP 
 PARTIALLY REMOVED 
 
 CUT SLIGHTLY 
 ALONGSIDE PLUMULE 
 
 INJURED AT EDGE 
 OF GERM AREA 
 
 PUNCTURED AT CROWN 
 
 HORNY ENDOSPERM 
 EXPOSED 
 
 RADICLE EXPOSED 
 
 TIP CAP 
 BROKEN OFF 
 
 SOUND 
 
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 10 20 30 40 50 60 70 80 90 100 
 PERCENT OF SOUND CHECK 
 
 E3 
 
 ^3 GROWTH INDEX 
 
 GREEN WEIGHT 
 
 Three methods of measuring seedling development. Seed with various types 
 of pericarp injury made by hand was inoculated at planting with Pythium 
 debaryanum or Penicillium oxalicum. Stand, green weight, and growth index 
 are adjusted here to give a value of 100 for the sound check. (For actual 
 stand percentages obtained in inoculation tests, see Table 14.) (Fig. 11) 
 
1957 
 
 Pericarp Ijcjuries in Seed Corn 
 
 41 
 
 near the plumule reduced stand, but as shown previously, these plants 
 had better vigor than plants from crown-injured seed. Results of the 
 seed inoculation experiments are shown graphically in Fig. 11. 
 
 Penicillium oxalicum. It was discovered early in these studies 
 (26) that the pathogenicity of this fungus is also greatly influenced by 
 pericarp injuries. The pericarp injury technique has subsequently been 
 used by other investigators working with P. oxalicum seedling blight in 
 corn (5, 31). The above-ground symptoms from P. oxalicum blight 
 vary with pericarp condition, the genetic constitution of the corn, and 
 with the temperature. The symptoms have already been described quite 
 well (5, 24, 31), but it is desired here to emphasize differences due to 
 the pericarp condition of the seed. Symptoms and severity of the dis- 
 ease when the seed has been inoculated appear to be the same in 
 natural soil as in disinfested sand. However, all data reported here are 
 from experiments with disinfested sand. 
 
 Temperature. The effects of Penicillium inoculations at different 
 temperatures varied widely, depending on the pericarp condition. At 
 70° to 80° F. when heavy spore loads were used, sound seed showed 
 normal growth until the two-leaf stage or later. Then characteristic 
 
 Leaf blight caused by Penicillium oxalicum starting at the tip ends of young 
 corn leaves. The dead area is blue-green at first, then turns drab or light 
 brown. (Fig. 12) 
 
42 
 
 Bulletin No. 617 
 
 I September, 
 
1957 
 
 Pericarp Inturies in Seed Corn 
 
 43 
 
 Variations in vigor of plants from pericarp-injured seed. One plant shows 
 only the pointed coleoptile. Others are in the one-, two-, and three-leaf 
 stages. (Fig. 14) 
 
 symptoms of leaf blight began to show (Fig. 12): dead streaks or 
 areas at the tips which are first dull blue-green in color, becoming dry 
 and brittle, later turning tan or drab. When the pericarps were injured, 
 vigor was affected more seriously than stand, especially at warm tem- 
 peratures (Fig. 13). Soil moisture, within broad limits, appears to have 
 little effect on the severity of blight caused by Penicillium oxalicum (5). 
 
 With the crown pericarp partially removed, at 70° to 80° F. many 
 of the coleoptiles emerged normally but stopped growing after they 
 were about 1 inch above the soil and remained closed (Figs. 13 and 14). 
 Some plants developed several leaves and continued to grow, but were 
 weak. Often the leaves of these plants were chlorotic at the start, soon 
 drying at the tips and edges. Such seedlings finally died in an erect 
 position. When the seed was kept at 50° F. for the first 10 days after 
 planting, there was no emergence at all from seeds injured at the 
 crown. Other types of pericarp injury had somewhat less severe effects 
 at this temperature (Table 15, Fig. 13). 
 
 Thus stands from injured seed were best at 80° F. and the most 
 damage from Penicillium blight occurred when the temperature was 
 50° F. during the first ten days after planting (Table 15). Johann ct al. 
 (24) reported the most damage from P. oxalicum seedling blight at 
 80° F. with reduced effects at lower temperatures. The writer also 
 observed a tendency toward more leaf blight at the 3-leaf stage at 80° 
 
44 Bulletin No. 617 [September, 
 
 than at 70° or 60° F. From the symptom descriptions, it appears that 
 Johann was working primarily with sound seed; therefore the effects 
 of increases in temperature were shown not in initial stand but as a 
 postemergence loss from blight. 
 
 Sparc concentration. P. oxalicum is remarkably effective at very 
 low spore loads. Seed with four pericarp conditions was tested at 
 widely different spore concentrations. The seed was planted in sterile 
 
 Table 15. — Effect of Temperature and Pericarp Condition on Stand, 
 
 Growth, and Leaf Blight in Plants From Seed Inoculated 
 
 With Penicillium oxalicum 
 
 (Hybrid U.S. 13, five pericarp conditions, inoculated with a spore suspension 
 
 and planted in disinfested sand at four temperatures. After 10 days at 
 
 60° or 50° F. those in the cold chamber were placed in a greenhouse 
 
 at 70°-75° F. until the threedeaf stage.) 
 
 D . .... Figure 13, 80° F. 70° F. 60° F. 50° F. 
 
 Pericarp condition ^ nQ g dayg n dayg 1Q dayg 1Q dayg 
 
 Stand (angle) 
 
 Crown injured 3 63 47 6 
 
 Injured near plumule 4 71 57 31 15 
 
 Injured over horny endosperm 6 84 65 57 27 
 
 Injured over radicle 5 87 76 55 33 
 
 Sound 2 90 87 87 85 
 
 Sound (check) a 1 90 90 90 87 
 
 L.S.D. (5-percent level) 7 7 7 7 
 
 Growth index" 
 
 Crown injured 3 26 22 0.3 
 
 Injured near plumule 4 49 38 13 2 
 
 Injured over horny endosperm 6 55 45 26 6 
 
 Injured over radicle 5 92 78 45 14 
 
 Sound 2 97 94 89 88 
 
 Sound (check)* 1 98 98 99 98 
 
 L.S.D. (5-percent level) 5 5 5 5 
 
 Plants with one or more blighted leaves (percent) 
 
 Crown injured 3 14 12 
 
 Injured near plumule 4 33 13 15 17 
 
 Injured over horny endosperm 6 17 10 13 13 
 
 Injured over radicle 5 13 11 10 17 
 
 Sound 2 12 15 10 17 
 
 Sound (check)* 1 7 11 2 8 
 
 L.S.D. (5-percent level) 7 N.S. 7 7 
 
 a This seed was not inoculated and was treated with Arasan at the rate of 2 oz. per 
 bu. However, some typical Penicillium leaf blight developed, infection coming from adjacent 
 inoculated rows. 
 
 >> Based on a value of 100 for a perfect stand of plants with 3 leaves (see page 11). 
 
 '' Based on number of plants that emerged from the soil. 
 
 
 
1957] Pericarp Injuries in Seed Corn 45 
 
 Table 16. — Effect of Spore Concentration on Stand, Plant Height, 
 
 and Leaf Blight in Plants From Seed Inoculated with 
 
 Penicillium oxalicum 
 
 (Hybrid U.S. 13 seed with various pericarp injuries made by hand, inocu- 
 lated with various spore suspensions. Seed was planted in disinfested 
 soil in 2-gallon cans, one inoculation and spore load to a can, and 
 kept in a greenhouse at 70°-75° F.) 
 
 Pericarp condition 
 
 Spore concentration r . y 
 
 (Number of spores per ml. water) Crown ove n r J h J ny J^ Sound 
 
 ^ y endosperm off 
 
 Stand (angle) 
 
 10,000,000 35.1 72.8 80.1 86.2 
 
 100,000 50.1 90.0 80.7 86.2 
 
 1,000 73.9 90.0 86.2 90.0 
 
 None (check) 86.2 90.0 90.0 90.0 
 
 L.S.D 9.8 9.8 9.8 N.S. 
 
 Average height per plant (centimeters) 
 
 10,000,000 1.8 5.3 16.4 17.5 
 
 100,000 1.8 8.7 16.1 17.5 
 
 1,000 2.3 11.6 16.6 17.7 
 
 None (check) 14.3 18.1 19.1 20.0 
 
 L.S.D 1.5 1.5 1.5 1.5 
 
 Plants with one or more blighted leaves (percent)' 1 
 
 10,000,000 13.0 37.5 16.0 .7 
 
 100,000 12.5 34.7 6.9 .7 
 
 1,000 16.7 15.3 1.4 
 
 None (check) 3.4 
 
 a Based on number of plants that emerged from the soil. 
 
 soil in 2-gallon cans, one seed condition and one spore load to a can. 
 This was done to prevent the inoculum from spreading within the soil 
 to the uninoculated rows, as in the previous experiment. 
 
 When the seed had pericarp injuries over the horny endosperm or 
 the tip cap broken off, spore concentration was positively correlated 
 with leaf blight (Table 16). Plant height was reduced at all concen- 
 trations for injury over the horny endosperm, but the effect became 
 more severe at higher spore loads. With crown injury, stand varied 
 according to spore concentration but plant heights were extremely poor 
 at all concentrations. The data in Table 16 show an apparent decrease 
 in blighted leaves at higher spore concentrations when the pericarp was 
 injured at the crown. These percentages actually occurred because most 
 shoots that emerged at high spore loads did not grow beyond the 
 coleoptile stage, and thus did not develop any leaves. 
 
46 
 
 Bulletin No. 617 
 
 [September, 
 
 Pythium debaryanum and Penicillium oxalicum gave quite 
 similar results, but nevertheless there was an interaction between or- 
 ganism and pericarp condition. This relationship was significant at the 
 5-percent level for stands and at the 1-percent level for growth index 
 and green weight per plant and per 100 seeds planted (Table 14). The 
 discrepancy between parallel results from the two fungi occurred pri- 
 marily among seed with slight crown injury. In that injury class P. 
 oxalicum caused much greater damage than P. debaryanum (Fig. 11). 
 Furthermore P. oxalicum was decidedly more damaging than P. de- 
 barya umn at warmer temperatures. 
 
 Aspergillus flavus and A. tamarii. These two species of Asper- 
 gillus cause a virescent condition in seedlings, primarily when the peri- 
 carp is broken. The plants are similar in appearance to that of some 
 inherited virescence types (Fig. 15). The ability of different isolates 
 to cause this effect varied widely. Both of these Aspergilli differed 
 markedly from Pythium and Penicillium isolates in their reaction to 
 various types of pericarp injury. Virescence occurred almost as fre- 
 quently when the seed was injured at the side of the kernel (only horny 
 endosperm exposed) as when the seed w r as injured at the crown. Much 
 
 Virescence caused by Aspergillus flavus inoculations of seed with the crown 
 pericarp injured. One healthy, and three virescent seedlings are shown. 
 Much of the leaf area was nearly white except for green color at the leaf 
 tips and some tendency toward green striping, as shown on the two plants 
 at right. (Fig. 15) 
 
1957] Pericarp Injuries in Seed Corn 47 
 
 less virescence occurred when the seed was injured at or near the 
 plumule. On the other hand, seed injured at the plumule had consid- 
 erably more damage from Pythium or Penicillium blight than those 
 with only the horny endosperm exposed (Table 14). Other details 
 about virescence induced by these Aspergilli have already been pub- 
 lished (30). 
 
 Other fungi. Inoculation experiments with other fungi were 
 only exploratory. Two pericarp conditions were used: sound and par- 
 tially removed from the crown. Seed was planted in 2-gallon cans, using 
 3 replications and one inoculation to a can, and placed in a greenhouse 
 at 70°-75° F. Nonsterile soil was used, as the interest at that time was 
 primarily in natural field soil. The test was repeated in different soil 
 the following year, with essentially the same results. Additional tests 
 were made in which the soil moisture was adjusted to 40, 60, and 80 
 percent of the moisture-holding capacity. 
 
 Stands from the checks (noninoculated seed, sound and with the 
 pericarp partially removed from the crown) were nearly 100 percent, 
 but plants from injured seed were low in vigor, averaging only 72.5 
 percent the height of plants from sound seed. No doubt this difference 
 in the vigor of the checks resulted from infestation by soil-borne fungi, 
 probably Pythium. 
 
 Inoculated seed with the crown pericarp injured gave different re- 
 sults, depending on the fungus isolate used. These results can be di- 
 vided into two classes: 
 
 No consistent effect different from that of the non-inoculated seed 
 with crown injuries occurred when Diplodia zeae, Gibber ella zeae 
 (three isolates), Aspergillus niger, and Trichoderma viride 1 inocula- 
 tions were made. This might indicate either that the fungus had no 
 pathological effect under the conditions of these experiments, or that 
 infestation by the pathogenic fungi naturally occurring in the soil was 
 retarded and the inoculum itself caused seedling damage. One excep- 
 tion was G. zeae which reduced both stand and vigor at low soil mois- 
 ture, compared with the check. This was also true of sound seed, 
 although the difference was greater for injured seed. It has been re- 
 ported that G. zeae inhibits certain Pythium spp. (9). 
 
 Vigor better than in check plants. Fusarium moniliforme (three 
 isolates), Penicillium notatum, and P. rugidosum caused plants from 
 injured seed to grow more vigorously than when it had not been inocu- 
 lated. The vigor approached, but did not equal, that of plants from 
 
 1 T. Hgnorum is considered a synonym according to Bisby (1). 
 
48 Bulletin No. 617 [September, 
 
 sound seed. This seems to indicate that these fungi had an antagonistic 
 or antibiotic effect on the pathogenic fungi in the soil. Edwards (7) 
 had observed an antagonistic effect of F. moniliformc (Gibbcrclla 
 fujikuroi). 
 
 Excepting Gibbcrclla zeae in dry soil, none of these organisms had 
 any significant effect on stand or plant height from sound seed. Seed 
 inoculations are often less effective than natural infection; results with 
 Diplodia zeae and G. zeae are outstanding examples. Furthermore, the 
 pathogenicity of isolates of some species varies widely. It seems prob- 
 able, however, that pericarp injury did not greatly predispose the seed 
 to seedling blight caused by the fungi mentioned, except Pcnicilliiim 
 oxalic um and certain Pythium species. 
 
 EFFECTIVENESS OF SEED TREATMENT 
 IN PROTECTING PERICARP- INJURED SEED AGAINST 
 SEEDLING-BLIGHT INFECTION 
 Effects on stand and yield 
 
 Cold tests. An experiment was described previously (page 23) 
 in which seed lots varying in the percentage of kernels with sound peri- 
 carps were given a cold test and the results measured in stand and 
 green weight per 100 seeds planted (Table 7). Part of the seed was 
 untreated and a duplicate sample was treated with Arasan at the rate of 
 yi ounce per bushel. Both stand and green weight were improved with 
 seed treatment, and doubled for the poorest seed. All stand increases 
 from treatment were significant at the 1 -percent level. On the other 
 hand, stand and green weight varied with the pericarp condition almost 
 as much with treated seed as with untreated, but the values for treated 
 seed were higher throughout. 
 
 Field tests. When stands from commercially processed seed 
 were compared with those from hand-handled seed in a three-year 
 field experiment, seed treatment increased both stand and yield, but 
 results from commercial seed with a great amount of pericarp injury 
 were still lower than those from hand-handled seed. The three-year 
 average given in Table 8 shows stands for untreated seed of 84.1 per- 
 cent for commercial samples, 93.6 percent for hand-handled seed. With 
 treatment, commercial seed produced a stand of 90.4 percent, hand- 
 handled seed 94.4 percent. The acre yields without treatment were 87.1 
 and 96.9 bushels, and with treatment, 94.2 and 97.3 bushels, respec- 
 tively. Average stands and yields from treated hand-handled seed with 
 
1957] Pericarp Injuries in Seed Corn 49 
 
 the pericarp partially removed from the crown were almost exactly 
 the same as those from treated commercially processed seed. When the 
 pericarp was sound, seed treatment did not produce any significant 
 increases in yield. The same results were obtained in another experi- 
 ment (Table 17). 
 
 In fairly normal weather and conditions similar to normal farm 
 practice, seed treatment gave about two-thirds control in stand and 
 yield from seed with the crown pericarp injured, compared with results 
 from hand-handled seed (Table 8). The differences in stand between 
 treated commercial and hand-injured seed on one hand, and treated 
 hand-handled (94-percent sound) seed on the other, were 4.0 and 3.3 
 percent respectively. These were significant at the 5-percent level. The 
 corresponding differences in yield — 3.1 and 3.2 bushels — were not 
 significant. 
 
 An average increase of 8.8 bushels per acre, or 10 percent, was 
 obtained with Arasan treatment of commercially processed seed in 
 field tests conducted from 1942 to 1955 at Urbana. The same degree 
 of increase was noted in the results of the three-year-test shown in 
 Table 8. 
 
 Under field conditions differences in vigor in the absence of differ- 
 ences in stand may or may not result in differences in yield. A case 
 where increases in yield from seed treatment were found, even though 
 treatment had not increased stand, has been reported (37, Table 4). 
 
 Importance of type of injury 
 
 In the annual tests conducted by the Illinois Station in 1954 and 
 1955 (Table 10) correlations were found between pericarp condition 
 and stand and yield, in spite of the fact that all seed used in the tests 
 had been treated with a protective fungicide before planting. 
 
 Another experiment was set up using seed from hand-handled ears 
 prepared so that there were four pericarp conditions: plumule exposed, 
 part of the crown pericarp removed, radicle exposed, and sound. Fig. 
 10, B and C, shows an exposed plumule and radicle. In this experiment, 
 exposed plumule caused much greater damage to stand and yield than 
 crown injury (Table 17). This was contrary to results from the cold 
 tests with injured seed (Tables 13, 14, and 15), but in this test the cut 
 was more severe, exposing the plumule visibly. Seed treatment caused 
 significant increases in stand and yield when applied to pericarp-injured 
 seed. Seed treatment at the rate of 1 ounce per bushel increased stands 
 as follows: plumules exposed, 121; crown injured, 56; radicle exposed, 
 
:-" 
 
 Bulletin No. 617 
 
 [September 
 
1957] Pericarp Injuries in Seed Corn 51 
 
 Table 17. — Effect of Seed Treatment on Stand and Yield From 
 
 Pericarp-Injured Seed in Field Test, Urbana, 1944 
 
 (Hybrid 111. 972-A1, part of the seed with pericarp injuries made with a knife 
 
 and part of each group treated with Arasan, 1 ounce per bushel) 
 
 p . Field stand Field stand Acre yield 
 
 condition Untreated Treated Untreated Treated Untreated Treated 
 
 perct. perct. angle angle bu. bu. 
 
 Plumule exposed 20.2 44.7 26.0 41.2 37.2 67.6 
 
 Crown injured 58.7 91.5 49.2 71.6 62.4 94.5 
 
 Radicle exposed 73.9 93.4 58.4 73.7 89.0 96.6 
 
 Sound check 92.9 94.6 73.8 74.7 98.9 99.5 
 
 L.S.D. (5-percent level) 4.5 4.5 8.1 8.1 
 
 26; and sound pericarp, 6 percent. None of the increases for sound 
 seed were significant. Stands and yields from seed with the plumule 
 exposed were very poor despite the high percentage increases from 
 seed treatment (Table 17). These results reinforce those obtained in 
 the cold tests: seed with the pericarp injured at the crown or plumule 
 is more susceptible to seedling blight than seed with the pericarp injured 
 over the radicle. The results of this experiment emphasize that seed 
 treatment often is effective only as a partial protection against seedling 
 blight when the pericarp is damaged. 
 
 Effect of temperature 
 
 Stand and green weights. Sound and injured seed of U.S. 13 
 was treated with several rates of fungicide and grown at 70° F. and 
 for three different periods at 50° F. in natural soil. 
 
 At 70° F., all stands were perfect (Table 18) and plants from all 
 seed conditions appeared to be good (Fig. 16, top left), but there were 
 some highly significant differences in green weights between plants 
 from sound and plants from injured seed. This was true even when 
 seed had been treated with 2 ounces of Arasan per bushel. 
 
 At 50° F. more important differences occurred, and interrelation- 
 ships between pericarp condition and seed treatment became apparent. 
 When the planted seeds were subjected to 50° F. for 10 or 20 days, 
 there were significant differences in stand and green weight between 
 the two rates of fungicidal treatment — 1/2 and 2 ounces per bushel — 
 among injured seed (Table 18). With sound seed, significant differ- 
 
52 Bulletin No. 617 [September, 
 
 Table 18. — Effect of Temperature and Rate of Seed Treatment on Stand 
 and Green Weight From Pericarp-Injured Seed in Cold Tests 
 
 (Hybrid U.S. 13, treated with Vi or 2 ounces of Arasan SF-X per bushel 
 
 and planted in naturally infested field soil. Seed was kept at 50° F. for 
 
 the first 5, 10, or 20 days or at a constant temperature of 70° F.) 
 
 Seed Fieurel6 Days at 50° F. 
 
 Pericarp condition treatment fe 
 
 (oz. per bu.) row no - 5 10 20 
 
 Stand (percent) 
 
 Injured at crown None 4 
 
 l A 5 
 
 2 6 
 
 Sound None 1 
 
 l A 2 
 
 2 3 
 
 Green weight (grams) 1 
 
 Injured at crown None 4 
 
 Vi 5 
 
 2 6 
 
 Sound None 1 
 
 ¥l 2 
 
 2 3 
 
 L.S.D. (5-percent level) 
 
 L.S.D. (1-percent level) 
 
 100 
 
 40 
 
 1 
 
 
 
 100 
 
 99 
 
 81 
 
 22 
 
 100 
 
 100 
 
 98 
 
 62 
 
 100 
 
 100 
 
 72 
 
 16 
 
 100 
 
 100 
 
 99 
 
 83 
 
 100 
 
 100 
 
 99 
 
 91 
 
 44 
 
 10 
 
 0.3 
 
 
 
 55 
 
 51 
 
 33 
 
 6 
 
 59 
 
 52 
 
 45 
 
 25 
 
 63 
 
 58 
 
 35 
 
 3 
 
 67 
 
 61 
 
 59 
 
 44 
 
 67 
 
 63 
 
 62 
 
 51 
 
 a dreen weight of plants from 100 seeds planted. 
 
 ences in stand were not noted until the cold period was 20 days. The 
 average ranking for the various seed conditions was as follows: 
 
 1. Most severe damage — untreated, pericarp-injured seed. 
 
 2. Injured seed treated with 1/? ounce Arasan almost same as 
 sound seed untreated. 
 
 3. Injured treated with 2 ounces per bushel. 
 
 4. Sound seed treated. Treatment with 2 ounces gave better results 
 than 1/2 ounce with seed subjected to 50° F. for 20 days. 
 
 Pythium infection. It has been shown that at 50° F. crown- 
 injured seed treated with Arasan was protected from infection for 12 
 days or more (Table 11), whereas in untreated seed infection occurred 
 in three days. However, after the roots were several inches long, the 
 ends of the roots from treated and untreated seed were equally sus- 
 ceptible to Pythium invasion. 
 
 At 60° F., although infection reached 100 percent on the sixth day 
 after planting in untreated, injured seed, there was very little infection 
 in treated seed whether sound or injured. 
 
1957] Pericarp Injuries in Seed Corn 53 
 
 Seed treatment was also partially effective against pre- and post- 
 emergence blight of seedlings caused by Penicillium oxalicum in crown- 
 injured seeds when this fungus occurred in the soil. Seed treatment did 
 not, however, guard against leaf blight (Fig. 13) after plants were in 
 the two- or three-leaf stage, regardless of the pericarp condition. 
 
 Effect of injury after treatment 
 
 Particularly in the planting process, pericarps may become injured 
 after the seed has been treated. An experiment was conducted using 
 two types of fungicidal treatment: a dust and a slurry. No sticker was 
 added other than that contained in the SF-X formulation. Treatments 
 were applied at three rates. The seed had been handled to insure, as far 
 as possible, freedom from pericarp injuries except those artificially 
 made by removing most of the crown surface. Some of the seed was 
 injured before and some after applying the fungicide. 
 
 The most interesting result was that treatment provided consider- 
 able protection even when injuries were made in the pericarp after 
 seed treatment. Stands were more than double those from untreated 
 seed, although they were much lower than those from sound seed 
 (Table 19). On the whole, an increase in the rate of application of 
 
 Table 19. — Effect of Pericarp Injury After Seed Treatment on Stands 
 in Cold Tests From Seed Treated With Arasan at Three Rates 
 
 (Hybrid U.S. 13, untreated and treated with i/£, 1, and 2 ounces Arasan per 
 
 bushel. Seed was planted in naturally infested soil and 
 
 kept at 50° F. the first 10 days.) 
 
 Seed Stand < an S le > 
 
 treatment Pericarp condition XT , ^ 01 
 
 (oz oer bu ) Not Dust Slurr y 
 
 K '' treated treatment treatment' 1 
 
 None Injured 18 
 
 Sound 68 
 
 3^2 Injured after treating 
 
 Injured before treating 
 
 Sound 
 
 Injured after treating. . 
 Injured before treating 
 Sound 
 
 Injured after treating. . 
 Injured before treating. 
 Sound 
 
 44 
 
 46 
 
 68 
 
 70 
 
 85 
 
 83 
 
 47 
 
 47 
 
 76 
 
 72 
 
 90 
 
 85 
 
 56 
 
 50 
 
 81 
 
 80 
 
 84 
 
 90 
 
 L.S.D. (5-percent level) 
 
 a Arasan suitable for use as a dust treatment. 
 b Arasan SF-X. 
 
54 Bulletin No. 617 [September, 
 
 fungicide gave somewhat better stands; some of the increases were 
 significant. There were no significant differences in results between 
 dust and slurry treatments. 
 
 EFFECT OF PERICARP CONDITION ON RESISTANCE TO 
 SEEDLING BLIGHT IN CORN INBREDS AND 
 SINGLE CROSSES 
 Resistance in inbreds 
 
 Eighteen inbreds with known reaction to Pythium (39) and Peni- 
 cillium (31) seedling blight were selected on availability of a sufficient 
 number of good ears produced under the same conditions. All were 
 produced in the same field in the same year by the Plant Breeding 
 Division, Agronomy Department, Illinois Agricultural Experiment 
 Station. Kernels from each ear were first treated with sodium hypo- 
 chlorite and then prepared by partially removing the pericarp from the 
 crown of one group, making a slight cut alongside the plumule in 
 others (Fig. 10, left), and leaving the third group sound. The seed 
 was inoculated at planting time w r ith a culture of Pythium debar yanum 
 or Penicillium oxalicum or left uninoculated as checks and planted in 
 formaldehyde-disinfested sand. Each replicate of 30 kernels consisted 
 of a composite from five ears. 
 
 Results are expressed only as stands. In the checks, germination 
 percentages of the composites were 95 to 100 percent (Table 20). 
 Disease also affects vigor, but there was an inherent difference be- 
 tween inbreds in seedling vigor. The inbreds are ranked in Table 20 
 according to their average resistance to each disease for the three peri- 
 carp conditions. The averages were derived after the stands for each 
 replication had been converted to angles. The ranking is slightly differ- 
 ent when arranged according to the actual stand percentages (Fig. 17). 
 
 Effect of pericarp condition. The ranking of the inbreds varies 
 considerably according to which pericarp condition is considered. In- 
 bred R4 when inoculated with Pythium (Table 20) is a good example 
 of nonconformity. Germination was perfect for seed with sound peri- 
 carps, but this inbred ranked among the poorest when the pericarp 
 was injured either at the crown or near the plumule. B10 gave opposite 
 results, ranking poorest of all in the sound pericarp classification but 
 comparatively better when the pericarp was injured. R4, 38-11, and 
 some other inbreds also showed considerable nonconformity in resist- 
 ance to Penicillium seedling blight (Table 20). The nonconformities 
 
1957] Pericarp Injuries in Seed Corn 55 
 
 were highly significant as indicated by the triple interaction between 
 pericarp condition, inbred, and pathogen used for inoculation. 
 
 Correlation of resistance between pericarp conditions. Consider- 
 ing all eighteen inbreds, there were some positive correlations between 
 the results in stand for the various pericarp conditions for each patho- 
 gen in spite of the nonconformities, as follows: 
 
 Pyt hium Penicillium 
 
 debaryanum oxalic it m 
 
 Sound with crown injury 0.557* 0.616** 
 
 Sound with injury near plumule 0.563* 0.156 
 
 Sound with crown and germ injury (aver.) 0.595** 0.766** 
 
 Crown injury with injury near plumule 0.545* 0.104 
 
 * Significant at the 5-percent level. 
 ** Significant at the 1-percent level. 
 
 The poor correlations between sound pericarps and injury near the 
 plumule and between crown and plumule injury with Penicillium 
 inoculations are due to the wide divergence of results for the different 
 kinds of injury in a few inbreds, especially 38-11. 
 
 100 
 90 
 
 40 
 
 20 
 
 PENICILLIUM OXALICUM- 
 
 - a i \ y \ a />^ 
 
 \ / 
 
 \ .J~^- ^ 
 
 I \.s r i 
 
 i 
 
 \ 
 
 < \ i 
 k 
 
 \ i 
 
 \ i 
 
 u 
 
 1 I I I 
 
 0h7 187-2 WF9 1205 R6I R4 BIO L289 W22 0S420 38-11 R2 A MI4 90 R59 Hy2 Tr 
 
 CORN INBREDS 
 
 Relative resistance of 18 inbreds, shown by comparative stands obtained 
 from seed inoculations with Pythium debaryanum and Penicillium oxalicum. 
 Stands shown here represent the average values for three pericarp condi- 
 tions: sound, injured near plumule, and partially removed from crown. The 
 correlation (0.470) between the tw r o values shown was significant at the 
 5-percent level. (Fig. 17) 
 
56 
 
 Bi i.i.i.nx No. 017 
 
 Table 20. — Effect of Pericarp Condition on Resistance to Seedling 
 
 Blight in Corn Inbreds as Shown by Stands From 
 
 Inoculated Seed in Cold Tests 
 
 (Eighteen inbreds, seed inoculated with Pythium debaryanum and kept at 50° F. 
 
 the first 7 days after planting or inoculated with Pcnicilliitiu oxalicum 
 
 and kept continuously in a greenhouse at 70° -75° F. a ) 
 
 
 
 
 
 Stand 
 
 
 
 
 
 
 
 Pericarp cond 
 
 ition of inoculated seed 
 
 
 Inbred Sound check, 
 
 
 
 
 Average, 
 inoculated 
 
 
 
 Injured 
 
 near 
 plumule 
 
 
 not inoculated* 
 
 Sound 
 
 Crown- 
 injured 
 
 seed 
 
 
 perct. 
 
 
 angle 
 
 angle 
 
 angle 
 
 angle 
 
 angle 
 
 
 
 Inoculated with Pythium 
 
 debaryanum 
 
 
 Oh7 
 
 100.0 
 
 
 90.0 
 
 56.8 
 
 6.5 
 
 37.8 
 
 33.7 
 
 187-2 
 
 100.0 
 
 
 90.0 
 
 62.8 
 
 6.5 
 
 39.2 
 
 36.2 
 
 WF9 
 
 95.0 
 
 
 77.1 
 
 56.8 
 
 25.5 
 
 37.0 
 
 39.8 
 
 R61 
 
 98.3 
 
 
 82.5 
 
 66.6 
 
 23.4 
 
 37.0 
 
 42.3 
 
 1.205 
 
 98.3 
 
 
 82.5 
 
 74.6 
 
 30.0 
 
 22.6 
 
 42.4 
 
 B10 
 
 96.7 
 
 
 79.5 
 
 56.1 
 
 33.2 
 
 48.7 
 
 46.0 
 
 R4 
 
 100.0 
 
 
 90.0 
 
 90.0 
 
 21.1 
 
 28.9 
 
 46.7 
 
 L289 
 
 100.0 
 
 
 90.0 
 
 74.6 
 
 33.9 
 
 38.4 
 
 49.0 
 
 W22 
 
 100.0 
 
 
 90.0 
 
 86.8 
 
 28.9 
 
 40.0 
 
 51.9 
 
 Os420 
 
 100.0 
 
 
 90.0 
 
 83.5 
 
 20.2 
 
 54.6 
 
 52.8 
 
 R2 
 
 100.0 
 
 
 90.0 
 
 80.8 
 
 34.7 
 
 57.7 
 
 57.7 
 
 A 
 
 98.3 
 
 
 82.5 
 
 83.5 
 
 33.0 
 
 57.6 
 
 58.1 
 
 M14 
 
 98.3 
 
 
 82.5 
 
 83.5 
 
 39.2 
 
 52.6 
 
 58.4 
 
 38-11 
 
 100.0 
 
 
 90.0 
 
 86.8 
 
 45.0 
 
 43.8 
 
 58.5 
 
 90 
 
 96.7 
 
 
 79.5 
 
 82.2 
 
 45.0 
 
 50.8 
 
 59.3 
 
 R59 
 
 100.0 
 
 
 90.0 
 
 90.0 
 
 50.9 
 
 49.3 
 
 63.4 
 
 Hy2 
 
 100.0 
 
 
 90.0 
 
 80.8 
 
 43.6 
 
 60.1 
 
 63.5 
 
 Tr 
 
 100.0 
 
 
 90.0 
 
 83.5 
 
 59.9 
 
 49.3 
 
 64.3 
 
 L.S.D. 
 
 (5-percent level) 
 
 
 8.7 
 
 7.6 
 
 7.9 
 
 
 
 
 Inoculated with Penicilli 
 
 um oxalicum 
 
 
 WF9 
 
 
 
 
 49.5 
 
 8.4 
 
 29.6 
 
 29.2 
 
 B10 
 
 
 
 
 
 57.0 
 
 24.0 
 
 23.2 
 
 34.7 
 
 Oh7 
 
 
 
 
 
 79.6 
 
 43.1 
 
 24.7 
 
 41.1 
 
 R2 
 
 
 
 
 
 76.8 
 
 41.9 
 
 31.4 
 
 50.0 
 
 1.205 
 
 
 
 
 
 73.6 
 
 43.7 
 
 33.2 
 
 50.2 
 
 M14 
 
 
 
 
 
 74.5 
 
 46.3 
 
 30.8 
 
 50.5 
 
 Tr 
 
 
 
 
 
 74.5 
 
 55.5 
 
 25.6 
 
 51.9 
 
 R4 
 
 
 
 
 
 86.7 
 
 27.3 
 
 42.5 
 
 52.1 
 
 L289 
 
 
 
 
 
 80.5 
 
 42.5 
 
 36.5 
 
 53.2 
 
 Hy2 
 
 
 
 
 
 90.0 
 
 58.5 
 
 26.3 
 
 58.3 
 
 W22 
 
 
 
 
 
 90.0 
 
 43.7 
 
 53.1 
 
 62.2 
 
 187-2 
 
 
 
 
 
 83.4 
 
 44.7 
 
 61.3 
 
 63.1 
 
 38-11 
 
 
 
 
 
 90.0 
 
 25.9 
 
 74.8 
 
 63.6 
 
 R59 
 
 
 
 
 
 90.0 
 
 40.9 
 
 64.3 
 
 65.1 
 
 A 
 
 
 
 
 
 86.7 
 
 54.2 
 
 59.4 
 
 66.7 
 
 Os420 
 
 
 
 
 
 86.7 
 
 70.2 
 
 45.8 
 
 67.6 
 
 90 
 
 
 
 
 
 90.0 
 
 77.8 
 
 40.5 
 
 69.5 
 
 R61 
 
 
 
 
 
 84.9 
 
 64.4 
 
 61.3 
 
 70.2 
 
 L.S.D. 
 
 (5-percent level) 
 
 
 11.0 
 
 15.0 
 
 13.3 
 
 
 a 
 
 Seed used as check was 
 
 treated 
 
 with Arasan and kept at 50° 
 
 F. 7 days after 
 
 planting. 
 
1957] Pericarp Injuries in Seed Corn 57 
 
 Correlation of resistance to two seedling diseases. When the 
 pericarp was sound, there was a highly significant correlation (0.705) 
 between resistance to seedling blight caused by Pythium and to that 
 caused by Penicillium among the eighteen inbreds. The correlation was 
 considerably lower (0.470) for the averages of all three pericarp con- 
 ditions, but these were still significant at the 5-percent level. Correla- 
 tions between resistance to the two diseases w r ithin either of the injured 
 pericarp groups were not significant. Divergences in ranking of the 
 inbreds' resistance to the two diseases due to differences in pericarp 
 condition were highly significant. 
 
 The irregularity of R61 was most striking. This inbred showed the 
 most resistance to Penicillium blight, but regardless of pericarp con- 
 dition, it was well below average in resistance to Pythium (Fig. 17). 
 R4 showed the most divergence between sound and injured pericarps 
 for both diseases; it ranked at or near the top of all inbreds when 
 sound, and among the lowest with any type of pericarp injury. 
 
 Resistance in single crosses 
 
 Six inbreds, differing widely in resistance were used in all pos- 
 sible combinations of single crosses. Sound seed and seed with crown- 
 injured pericarps were planted in naturally infested soil. Reciprocal 
 crosses were planted in the trays as paired rows. Sound seed was kept 
 at 50° F. for 14 days, crown-injured seed for 5 days. 
 
 Different crosses produced widely different stands, but the two 
 pericarp conditions for each cross gave quite similar stands. The cor- 
 relation for stands between the two pericarp conditions for the thirty 
 crosses was highly significant. But there was also a fairly consistent 
 difference. The difference in stands between crosses with susceptible 
 ear parents and those with resistant ear parents was generally greater 
 when the pericarp was injured than when it was sound (Table 21). 
 
 Comparing average stands for each inbred when used as an ear 
 parent (Table 21, last column) with stands for the inbreds (Table 21, 
 second column), some similarity appears. Oh7, which ranked lowest 
 when tested as an inbred, also averaged lowest in crosses in which it 
 was used as an ear parent. WF9 and 187-2 ranked low, close to Oh7 
 as inbreds; they also ranked below average as ear parents, but well 
 above Oh7. The resistant lines — Hy2, 90, and R59 — showed similar 
 behavior when tested as inbreds, but R59 contributed much more 
 resistance in the single crosses. 
 
 Influence of ear parent. A strong maternal influence on cold 
 
58 
 
 Bulletin No. 617 
 
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1957] Pericarp Injuries in Seed Corn 59 
 
 test results has been reported in the literature (40, 43). This influence 
 was also found in these experiments. When inbreds were used as ear 
 parents, the average results were quite similar to those obtained from 
 inbred testing. However, when these same inbreds were used as pollen 
 parents there was no similiarity, and little average difference between 
 crosses. This was true regardless of the condition of the pericarp. No 
 doubt, this effect was due largely to the fact that the ear parent con- 
 tributes twice as many chromosomes to the endosperm as the pollen 
 parent. In addition, Hooker and Dickson found a disproportionate 
 amount of maternal influence when the embryo is tested for suscepti- 
 bility to Pythium debar yanum in the absence of the endosperm, but the 
 effect was not great (15). 
 
 Influence of pollen parent. Although the influence of the pollen 
 parent was much less pronounced than that of the ear parent on resist- 
 ance, the pollen parent did have some significant effects. However, the 
 effect was unpredictable from the reaction of the inbred. This was 
 illustrated by the behavior of 187-2 which rated comparatively sus- 
 ceptible as an inbred but gave the highest average score for resistance 
 when used as a pollen parent. Its superiority was significant at the 
 5-percent level. Oh7, the most susceptible inbred, when used as a pollen 
 parent gave results as good as those rated resistant. Pinnell (40) 
 obtained similar results with eight entirely different inbreds; an inbred 
 rated as good in the cold test and one rated as poor gave exactly 
 opposite results when used as pollen parents in crosses. However, these 
 were exceptions to the rule. 
 
 Hy2, 90, and R59 were rated as comparatively resistant to Pythium 
 debaryanum, as inbreds. When tested in single crosses, R59 as an ear 
 parent was much superior to the others, but when used as a pollen 
 parent this inbred contributed the least resistance of all six (Table 21). 
 
 These results indicate a very complex genetic situation and prob- 
 ably cannot be explained by any simple heritable relationship. 
 
 CONTROL OF SEEDLING BLIGHT IN DENT CORN 
 
 The prevention of losses in stand and yield from seedling blight 
 disease enhanced by pericarp injuries in the seed can be approached 
 from three directions: avoidance of pericarp injuries, seed treatment, 
 and genetic resistance and combining ability. Attention to all three is 
 essential, since pericarp injuries cannot be altogether eliminated, and 
 neither of the other possible means of control is completely effective. 
 
60 Bulletin No. 617 [September, 
 
 Other seed conditions affecting the development of seedling blight are 
 maturity (28, 41), age (28, 41), environmental conditions during the 
 growing season (14), and the presence of certain fungi on or within 
 the seed (29). 
 
 Avoidance of pericarp injuries 
 
 Immature seed is more subject to pericarp damage. As the results 
 of these experiments show, immature seed is much more susceptible to 
 spontaneous cracking of the pericarp during the drying process than 
 mature seed. When subjected to a mechanical hazard, such as dropping 
 on a stone Moor, even moderately immature seed is subject to more 
 pericarp damage than mature seed. Wright (47) has suggested that 
 harvesting be delayed until the moisture content is between 27 and 30 
 percent. 
 
 Shelling at moistures above 12 percent zvas damaging. The detri- 
 mental effect of shelling at high grain moistures has been reported 
 here. Damage to seed increases as moisture at shelling rises above 12' 
 percent, and is also higher at lower moistures. Moisture in the cob, as 
 well as in the seed, should be considered to avoid tip-cap damage. Byi 
 allowing drying bins to cool a day before shelling, seed and cob 1 
 moistures can be equalized and tip damage prevented (47). 
 
 Some of the pericarp injury in commercial seed coidd be avoided by< 
 careful handling. In the samples examined, commercial seed averaged 
 only about 22 percent sound kernels. Since considerable variations in' 
 the prevalence of pericarp injuries were noted between samples from; 
 different producers, it seems possible that much improvement can be( 
 made in methods of handling and processing seed. 
 
 Methods and equipment need to be adjusted. In his excellent dis-J 
 cussion on avoiding pericarp damage, Wright (47) stressed the point 
 that much of the commercial equipment now in use has been designed 
 for feed corn, and new equipment and methods will be required to 
 reduce pericarp damage to seed corn. Progress is being made in this 
 direction by some manufacturers. Seed processors have improved seed 
 quality by operating shellers and conveyors at much lower speeds than 
 the manufacturers recommend. Other improvements can be made by 
 altering present machinery and methods. Some of his suggestions were: 
 
 Remove pegs from the snapping rolls of corn pickers and replace 
 the husking rolls with rubber ones. 
 
 Avoid picking too clean and rely on removing husks before the 
 corn enters the drying bins. 
 
1957] Pericarp Injuries in Seed Corn 61 
 
 Use rubber elbows in conveyor pipes through which seed flows by 
 gravity; forced-air conveying can be very damaging to the seed. Also, 
 rubber conveyor belts, rubber buckets, or rubber flights can be helpful. 
 
 Cylinder graders cause more damage than flat-screened vibrator 
 types. 
 
 Cylinder shellers for seed corn should have lugs well-worn by use 
 on feed corn, or dressed to the shape of smooth, well-rounded knobs. 
 
 Cushion the fall of ear and shelled corn with canvas chutes and 
 rubber padding. Chutes that are too steep are damaging; spiral and 
 zig-zag arrangements help to slow the speed of descent. 
 
 Cup elevators produce less damage if fed at the bottom of the 
 down-leg side. Speed should be slow, but additional cups may be added 
 to maintain capacity. Discharge the seed on an abrasion rubber pad. 
 
 Vibrator feeders, either magnetic or mechanical, help by providing 
 a constant flow to elevators and processing machinery; they can readily 
 be adjusted to various speeds. 
 
 A systematic check can locate the source of damage. Most process- 
 ing plants have developed their own systems of operation and handling; 
 thus no uniform recommendations for reducing pericarp damage can 
 be given. A good way of finding out where the trouble spots in the 
 process are, is by staining a sample of seed and making a systematic 
 check after each operation. Then adjustments such as those suggested 
 above can be made to cut down damage in the more important sources. 
 
 Seed treatment 
 
 Seed treatment prevents much of the loss from seedling blight, but 
 has not yet been developed to give complete control. Treating seed with 
 a recommended fungicide at an adequate rate will give about two-thirds 
 control over losses in yield that might result with untreated seed having 
 a great amount of pericarp injury. Most processing plants have adopted 
 this practice. 
 
 Resistance in inbreds and crosses 
 
 Resistant inbreds or single crosses have greater influence when used 
 as car parents. The present use of a certain inbred in a cross is deter- 
 mined almost entirely on characters other than seedling blight resist- 
 ance. Although results of these tests show that resistance of certain 
 lines may differ with various pericarp conditions, it is generally an 
 
62 Bulletin No. 017 [September, 
 
 advantage to use the most resistant inbred or single cross as an ear 
 parent, because the ear parent has a larger influence on the suscepti- 
 bility of the resulting cross to seedling blight. 
 
 t I cold test can be used to determine relative resistance. Consider- 
 able differences in resistance have been shown between inbreds as well 
 as between crosses (Table 21). If a producer wishes to determine the 
 resistance of his inbreds or crosses, he can do so with a cold test of 
 his own seed, the simplest method being the one described by 1 loppe 
 (19). The samples tested should each involve a number of ears of the 
 same pedigree; all inbreds or hybrids being compared should have been 
 produced in the same year under the same conditions (13, 14, 40). It 
 does not appear to make much difference whether the pericarps are 
 sound or injured, but they should be alike. Because it is so difficult to 
 assure sound pericarps, even with careful handling, it would be advis- 
 able to injure all the seed at the crown before testing. 
 
 DISCUSSION 
 
 Examinations of many samples of commercial seed corn made in 
 each of ten years showed considerable variation from year to year in. 
 the amount and kinds of pericarp injury, but during the thirteen-year' 
 period there was no apparent trend toward improvement. The data 
 indicate that (a) samples from some seed processors average consider-' 
 ably less injury than those from others; (b) samples from one 
 processor may be higher than average in one type of pericarp injury 
 while those from a different processor may be higher than average in a 
 different type; (c) samples of the same hybrid obtained from different 
 processors may vary greatly in the amount of injury; and ( d) samples 
 of different hybrids from the same processor may vary considerably 
 There may be differences between samples of the same hybrids from 
 one processor, if they are obtained from different fields, but this ha- 
 not been investigated. 
 
 At least four factors appear to be responsible for the difference? 
 between samples in the prevalence of pericarp injury: moisture con- 
 tent of the grain when harvested, handled, and processed; maturity of 
 the seed, genetic nature of the seed, and type of mechanical handling 
 and manipulation. All of these are somewhat under the control of the 
 seed producer and processor and no doubt improvements can be made 
 in many cases. 
 
 Shelling at high moisture increased pericarp damage greatly. Doubt- 
 less no one would shell seed corn at the maximum moistures used ir 
 these experiments, but since similar results were obtained with twe 
 
 
1957] Pericarp Injuries in Seed Corn 63 
 
 shellers operating on different principles, a similar effect, although 
 probably less acute, might be expected in other mechanical manipula- 
 tions. In samples obtained from a commercial processing plant, Wort- 
 man and Rinke (46) found that the sheller was the most important 
 single cause of pericarp injuries. Harvesting experiments with a 
 picker-sheller (3) and a grain combine (16) have demonstrated a 
 great increase in kernel damage with increases in grain moisture. 
 
 Not much experimental data are available on the effect of ma- 
 turity on the susceptibility of seed corn to pericarp damage. In some 
 earlier work the writer found a considerable increase in pericarp in- 
 jury in immature seed compared with mature seed after hand-handled 
 ears had been dried (28). These injuries occurred primarily on the 
 part of the kernel nearest the cob. In the experiment reported in this 
 bulletin this effect occurred again to a significant extent. In some other 
 immature seed samples, a considerable amount of blistering was 
 observed. Immature kernels are also more subject to injury from 
 mechanical hazards than mature seed. Wortman and Rinke (46) re- 
 ported this observation in mechanically processed seed; the same con- 
 clusion was reached from an experiment reported here (Table 4). 
 Immature seed was more subject to injury when it had been dropped 
 15 feet onto a smooth stone floor. Differences between mature and im- 
 mature seed in susceptibility to this type of damage may be even 
 greater than the data show, since the immature seed is lower in specific 
 gravity and less smooth than mature seed and therefore probably at- 
 tains less velocity in falling. 
 
 Corn and flax are two crops known to be especially susceptible to 
 seedling blight when the pericarp is broken and not protected by a 
 fungicide. If seed could easily be produced free from pericarp injury, 
 seed treatment could probably be recommended only for certain 
 special conditions. 
 
 A very surprising result in a cold test was the superior performance 
 of carefully hand-picked and hand-handled seed compared with that 
 of seed selected as sound from commercial samples obtained from the 
 same seed-producing field. The cause of the difference was not ascer- 
 tained. Three apparent differences in preparation of the seed occurred: 
 in drying methods; subjection to shock, which was considerable in me- 
 chanical shelling but carefully avoided with the hand-picked seed; and 
 selection — hand-picked ears were limited to those that were fully 
 developed and free from molds and injuries. 
 
 Better stands were obtained from pericarp-injured seed in the 
 cold tests when the period at low temperature was delayed for several 
 
"4 Bulletin No. 617 [September y 
 
 da\s after planting. The effects of disease damage decreased, and the 
 differences between resistant and susceptible hybrids were minimized 
 whether results from sound or pericarp-injured seed are considered 
 (Table 12). It has been observed by the writer that in the field, the 
 onset of unfavorable temperatures several days after planting is less 
 detrimental to stand and the effect of fungicidal treatment less pro- 
 nounced than when they begin earlier. These results agree partially 
 with those reported by Hooker and Dickson (15): that resistance to 
 seedling blight may build up fairly rapidly under conditions favorable 
 for germination. This effect could probably have been counteracted by 
 following the initial warm period by a longer period of time at low- 
 temperature. 
 
 Several investigators have recognized that not all kinds of pericarp 
 injuries are equally important, and each has devised a system of classi- 
 fication. Wortman and Rinke (46) found that chips broken off are 
 responsible for more serious damage to seedlings than a small crack in 
 the pericarp. This agrees with results reported here which show that 
 removal of one- fourth or more of the crown pericarp allowed more 
 disease damage in cold tests than less extensive injuries at the crown. 
 Injuries on the face of the germ were divided into two classes, since 
 early in this work (23) it was observed that injuries over the plumule 
 are much more important than those over the radicle. 
 
 In commercial seed when one- fourth or more of the crown pericarp 
 was missing, the effect on stand was more severe than the average for 
 injuries over or near the plumule (Table 9). Injury at the crown often 
 involves a much larger area than injuries at or near the plumule. 
 Compared with the average injuries — ranging from slight cracks up 
 to nearly one-fourth of the crown — injury over the plumule usually 
 was the most important with respect to stands. This w r as also generally! 
 true for hand-made injuries. An exception occurred in a field test 
 (Table 17), where exposure of the plumule caused much more damage 
 to stand and yield than removal of most of the crown pericarp. Plow- 
 ever, in this experiment a small piece of pericarp was actually removed 
 from the germ area, visibly exposing the end of the plumule. Tatum 
 and Zuber (44) reported a similar effect in a cold test, and Livingston 
 (33) found that peeling a strip of pericarp from the germ area had 
 a more detrimental effect than peeling a similar strip of pericarp from 
 the crown. There seems to be general agreement that when the pericarp 
 injuries are of similar kind or magnitude, the effect on stand is most 
 severe when the injury occurs at or near the plumule. 
 
 A curious fact, not mentioned by others, is that regardless of 
 
1957] Pericarp Injuries in Seed Corn 65 
 
 stand plants produced by crown-damaged seed were much lower in 
 vigor than plants produced by seed with injuries over the plumule 
 (Tables 9, 14). This was true regardless of the extent of crown 
 damage, whether the injury occurred in processing or was artificially 
 made, and whether the blight was caused by Pythium debaryanum or 
 Penicillhim oxalicum. 
 
 Several species of Pythium and Penicillium oxalicum are the only 
 organisms now known to be very greatly influenced in their capacity 
 to cause severe seedling blight by the pericarp condition of the seed. 
 Pythium species occur almost universally in cultivated soil, but appar- 
 ently their kinds, abundance, and virulence vary. P. oxalicum, fortu- 
 nately, does not occur very extensively in soil; when the seed pericarp 
 is injured, this pathogen is very damaging in minute amounts. Natural 
 Penicillium seedling blight occurring in farm practice appears to result 
 more frequently from seed-borne than from soil-borne infestation. 
 
 When seed with sound pericarps was planted in naturally infested 
 soil and kept at 50°, 60°, or 70° F., no Pythium infection took place 
 until one to several days after the pericarp had broken due to growth 
 processes (Table 11). Infection was still further delayed and dimin- 
 ished when the seed had been treated with a protective fungicide. On 
 the other hand, when the pericarp had been physically damaged, and 
 seed not treated, fungi penetrated the pericarp almost immediately 
 after planting. 
 
 In testing the effects of pericarp injuries on seedling-blight develop- 
 ment at low temperature, some investigators treated the seed with a 
 protective fungicide. Similar gradients were obtained in parallel tests 
 made by the writer with and without seed treatment, but the stands 
 were considerably higher throughout for treated seed (Table 7). The 
 tests can be adjusted to obtain similar stands by exposing treated seed 
 to a longer cold period. For example, a 40-percent stand from seed 
 with the crown pericarp partially removed was obtained in five days at 
 50° F. ; a similar stand could be obtained from the same type of seed 
 treated with Arasan, Yl ounce per bushel, by extending the cold period 
 to 10 to 20 days (Table 18). The same principle can be applied in 
 testing different rates of fungicidal treatment on seed of the same peri- 
 carp condition: in a five-day cold test, 1/2 ounce and 2 ounces of 
 Arasan per bushel gave equal control with crown-injured seed, but in 
 a ten-day test, the 2-ounce rate was significantly better. 
 
 When testing different kinds of corn for resistance to seedling 
 blight, in most cases it does not appear to be of very great importance 
 whether the pericarps are sound or injured. What is most important 
 
66 Bulletin No. 617 [September, 
 
 is that they be alike for all entries being compared. Furthermore, it 
 should not be assumed that they are alike just because no pericarp 
 injuries have been made intentionally. Resistance is only relative. The 
 most resistant line, with a considerable part of the crown pericarp 
 removed from all kernels, can be expected to rank similar to the most 
 susceptible line with all pericarps sound when tested under the same 
 conditions. Unless exceptional care has been used in handling to assure 
 sound pericarps, it would seem best to injure all the seed at the crown 
 before testing. Injuries at the crown are made more quickly than those 
 over the plumule and in practice have also resulted in less variability in 
 results. Further, in commercial use, injured pericarps are more com- 
 mon than sound, some inbreds rank quite differently when the peri- 
 carps are injured, and a test of seed with injured pericarps requires 
 less time at low temperature. 
 
 Some preliminary experimentation is required to determine the 
 desired time of exposure to low temperature in a cold test. The disease 
 effect obtained is influenced by the infective potential of the soil, the 
 nature of the seed being tested, soil moisture, and other factors. If the 
 time at low temperature is too short, for example, an inbred of inter- 
 mediate susceptibility may produce a full stand and appear to be as 
 good as the most resistant line tested. If the test is too severe, only the 
 most resistant entries will produce any stand, and the others will ap- 
 pear to be equally susceptible. In some cases, of course, it is desired 
 only to detect the most resistant lines. 
 
 In the production of crosses, the susceptibility to Pythium seedling 
 blight depends largely on the susceptibility of the ear parent, regard- i 
 less of whether it is an inbred or single cross. In single crosses an 
 inbred with known resistance to Pythium seedling blight should be used j 
 as the ear parent unless there are other reasons to prevent it. However, . 
 the susceptibility of F 1 seed to seedling blight was also influenced to 
 some extent by the pollinator. The tests of single crosses reported here 
 were very limited in number, but the data indicate that while the effect 
 of the pollen parent is appreciable, the result cannot be predicted from 
 its resistance rating as an inbred. The actual comparative resistance of 
 hybrid seed of any genetic composition must be determined by test, 
 because of differences in combining ability. Results may also differ 
 between seed lots due to the environment during the growing season 
 and other factors. Inbreds that have been grown by different seed 
 producers for some years have been found to differ considerably in 
 their resistance to seedling blight. 
 
1957] Pericarp Injuries in Seed Corn 67 
 
 SUMMARY 
 
 Samples of commercial seed corn were found to vary considerably 
 in the amounts and kinds of pericarp injury. Many seed samples of 
 commercial hybrids were examined in each of ten years over a thirteen- 
 year period. A staining technique, adapted in 1951, enabled many 
 pericarp cracks to be detected that could not be seen otherwise. After 
 staining, commercial seed was found to average only about 22 percent 
 sound kernels. There was no apparent trend toward a reduction in 
 pericarp injury during the period. 
 
 Shelling at high moisture increased pericarp damage. The amount 
 of injury increased rapidly as the grain moisture content rose above 
 12 percent to 29 or 34 percent, and there was a tendency for damage to 
 increase at moistures below 12 percent. 
 
 Immature seed was more subject to pericarp damage than mature 
 seed. Very immature seed had a higher incidence of spontaneous peri- 
 carp cracking during the drying process, and when seed was subjected 
 to identical mechanical hazard by dropping 15 feet onto a stone floor, 
 even slightly immature seed showed more susceptibility to injury than 
 mature seed. In this test, three hybrids differed significantly in the 
 amount of pericarp injury caused by an identical mechanical hazard. 
 
 Pericarp injury also appeared to be influenced somewhat by grade 
 size; there was a tendency for damaged kernels to increase as grade 
 size increased. Damage tended to occur more frequently in the 
 "rounds" than in the "flats." 
 
 Better stands were obtained from carefully handled hand-picked 
 seed than from sound kernels selected from commercially processed 
 seed. Severe crown injuries had the most serious effect on stand. The 
 different types of pericarp injury ranked as follows in the severity of 
 their effect on stand: severe crown injury, injury over or near the 
 plumule, slight crown injury, injury at margin of germ area, other 
 pericarp injuries, injury over the radicle, and tip cap broken off. 
 
 Vigor of plants was affected more severely by crown injuries, 
 whether severe or slight, than by injury over the plumule with seedling 
 blight caused by either Pythium debar yanum or Pemcillium oxalic ion. 
 When different rates of planting were used in a field test, it was deter- 
 mined that acre yields from crown-injured and sound seed differed 
 significantly even when stands were the same. 
 
 The prevalence of each type of pericarp injury was correlated 
 negatively with stand and yield in field tests, although the seed had 
 been treated with a fungicide. Thirty-six samples of commercial seed 
 corn used in the 1954 and 1955 hybrid corn tests made by the Illinois 
 
68 Bulletin No. 617 [September, 
 
 Station were examined for pericarp injuries. Highly significant cor- 
 relations between stand and yield were noted in both tests, and the 
 percent of sound kernels per sample was positively correlated with 
 stand and yield. Some of these relationships were highly significant. 
 This sort of correlation is likely to occur only under conditions espe- 
 cially conducive to seedling blight. 
 
 Striped plants were observed in field plantings in two different 
 years; they occurred only when the seed had pericarp injuries, and it 
 was shown that this striping was not heritable. 
 
 High soil moisture improved growth in plants from sound seed, 
 but increased disease damage to pericarp-injured seed. When experi- 
 ments were conducted with naturally infested soil adjusted to three 
 levels of moisture content, only stands from injured seed decreased at 
 higher moistures. The green weight of plants from sound seed im- 
 proved at higher soil moistures. 
 
 Exposure to cold temperature immediately after planting had the 
 most severe effect on stand from pericarp-injured seed. When the cold 
 period was delayed for several days, improved stands were obtained 
 from injured seed, and the differences in stand between susceptible and 
 resistant hybrids, as well as sound and injured seed were reduced. 
 
 Pythium species were the first invaders of seed planted in moist 
 field soil. Of those species identified, Pythium debaryanum appeared to 
 occur most frequently. Sound seed was fully protected against invasion 
 until after the pericarp had split open due to growth. In seed with 
 pericarp injuries, invasion occurred much earlier. 
 
 Pythium debaryanum and Penicillium oxalieum were the only or- 
 ganisms found in seed inoculation tests to be greatly influenced by the : 
 pericarp condition of the seed in their ability to cause seedling blight. 
 Results with these two organisms, regarding the degree of disease ; 
 damage caused with seed differing in pericarp condition, were some- 
 what similar. The main difference was that P. oxalic urn was more 
 active in the slight crown injury class. This pathogen was found to be 
 very damaging even at very low spore concentrations. 
 
 Aspergillus flams and A. tamarii in inoculation experiments caused 
 virescence rather than seedling blight. The effect was most pronounced 
 with injury at the crown or at the side of the kernel, and not as notice- 
 able with injuries on the face of the germ. 
 
 Considerable increases in stand and yield were obtained by the use 
 of seed-treating fungicides. Yield data show that treatment of com- 
 mercial seed averaging only about 19 percent sound kernels gave about 
 two-thirds control over seedling blight, compared with yields from 
 
1957] Pericarp Injuries in Seed Corn 69 
 
 hand-picked, hand-handled seed that had a low incidence of pericarp 
 injuries. When crown injuries were made after the seed had been 
 treated, treatment was about half as effective. Seed treatment did not 
 control Pythium rot at the end of seminal roots, nor was it effective 
 against Penicillium oxalicum leaf blight in infested soil after seedlings 
 had reached the two- or three-leaf stage. 
 
 In held tests with sound and injured seed in four different years, 
 seed treatment gave no significant increases in yield where the pericarp 
 was sound. But over fourteen years, in tests with commercially 
 processed seed, an average increase of 8.8 bushels per acre, or 10 per- 
 cent, was obtained with the use of Arasan. 
 
 The ranking of inbreds according to their resistance to seedling 
 blight was affected by the pericarp condition of the seed as well as by 
 the pathogen. Eighteen inbreds were tested for resistance to Pythium 
 deharyanum and Penicillium oxalicum, and three pericarp conditions 
 were used. In general, there were some significant relationships be- 
 tween the pericarp conditions and the ratings of the inbreds in resist- 
 ance to each fungus, as well as their relative resistance to the two 
 diseases. But some inbreds ranked very differently for different peri- 
 carp conditions, while others ranked differently in resistance to the 
 two diseases. These differences were significant as tested by the inter- 
 action between inbred, pericarp condition, and pathogen. 
 
 In tests of single crosses involving six inbreds — three susceptible 
 and three resistant to Pythium deharyanum — a strong maternal influ- 
 ence was found on resistance to seedling blight. Crosses made up with 
 susceptible inbreds as ear parents averaged more susceptible to Pythium 
 seedling blight than those with comparatively resistant ones. There was 
 also a significant paternal influence on resistance, but the effect could 
 not be predicted from the inbred rating. Some susceptible inbreds used 
 as pollen parents gave a better average for resistance than some resist- 
 ant inbreds. These relationships were the same regardless of whether 
 seed with sound or crown-injured pericarps was used. 
 
 Control of seedling-blight damage enhanced by pericarp injuries in 
 the seed can be approached in three ways: new methods and adjust- 
 ment of equipment used in processing seed can help to reduce the high 
 incidence of pericarp injuries; seed treatment with a good fungicide 
 at an effective rate can produce better stands and yields from seed 
 with a great amount of injury than could be expected without protec- 
 tion; and the use of resistant inbreds and single crosses as ear parents, 
 while subject to other factors, is probably the most effective way to 
 obtain resistance to blight, regardless of the seed-pericarp condition. 
 
70 Bulletin No. 617 [September, 
 
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1957] Perigarp Injuries in Seed Corn 71 
 
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11 Bulletin No. 617 
 
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