April 1948 E-745 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine CORN EARWORM RESISTANCE IN SWEET CORN INBREDS AND HYBRIDS By E. V. Walter Division of Cereal and Forage Insect Investigations Much effort has been made during the past several years to find in- breds and hybrids of sweet corn resistant to the corn earworm (Heliothis armigera Hbn.). This work has been done in cooperation with the sweet corn breeders of several State agricultural experiment stations and the Bureau of Plant Industry, Soils, and Agricultural Engineering of the U. S. Department of Agriculture.!/ Some of the information obtained has been assembled in this paper for the convenience of plant breeders and ento- mologists interested in corn improvement. The following tables show the general reaction of some of the inbreds and hybrids tested. Many experimental inbreds and hybrids, including some of those listed in the tables, have been discarded because of agronomic or other weaknesses. Most of those discarded reacted as intermediate or susceptible to earworm injury, although a few that were poor agronomically appeared to have a rather high degree of resistance. Inbred selections in some of these are being attempted. l/ Seed used in these tests has been furnished by 7/. Ralph Singleton, Connecticut Agricultural Experiment Station; Walter A. Huelsen, Illinois Agricultural Experiment Station; E. S. Haber, Iowa Agricultural Experiment Station; J. B. Park, Ohio Agricultural Experiment Station; Glenn M. Smith, U. S. Bureau of Plant Industry, Soils, and Agricultural Engineering and Purdue University Agricultural Experiment Station; Charles F. Poole, U. S. Bureau of Plant Industry, Soils, and Agricultural Engineering, Charleston, S. C. In addition to the material furnished by the several breeders, a few varieties and hybrids have been purchased in the open market for testing. A few selections made by the writer and a few made in cooperation with R. A. Blanchard of this Bureau and R. 0. Snelling of the Bureau of Plant Industry, Soils, and Agricultural Engineering are included. A number of experimental crosses between tested inbreds have been made by members of these two Bureaus for our studies on inheritance of resistance. These are included in table 3. - 2 - The reaction of many of the strains to natural infestation was observed at Weslaco, Tex., where a heavy and quite uniform infestation cou}.d be expected each year. At Lafayette, Ind., and Urbana, 111., where there was less likelihood of a uniformly heavy infestation, the natural infestation was supplemented by the placing of 3 newly hatched larvae on the silks of each ear 3 to 5 days after emergence, and 3 more similar larvae on the silks of the same ears 2 to 3 days later. The damage was usually appraised at the roast ing-ear stage after the larvae had left the ear. Most varieties reacted the same to the natural infestation as they did to the artificial or supplemented infestation. There were a few exceptions, however, the most notable of which was inbred P53, which was highly resistant to natural infestation wherever tested, but reacted as a susceptible when the larvae were placed on the ears under the selfing bags. It reacted as a susceptible when used in crosses. Egg counts showed as many eggs on P51 as on other inbreds. Such exceptions are noted in table 1. After the larvae had matured, the ears were gathered and husked to evaluate the damage. The infested ears were placed in 5 classes, accord- ing to the amount of feeding done, as follows* Class 1, tip only; class 2, kernels to -g- inch below the tip; class 3» kernels to 1^- inches below the tip; class 4, kernels to 2^ inches below the tip; and class 5» kernels exceeding 2£ inches below the tip. Butt or side injury was placed in one of the above classes, depending on the location and amount of trimming necessary to make a usable ear. The percentage of ears in each class could then be determined. Counts of the injured kernels on several thousand ears, after dividing into classes as described above, showed the number of average-size kernels destroyed to be approximately as fellows: Class 1, less than 1; class 2, 10; class 3> 20; class 4, 30; and class 5» 40. Multiplying the percentage of ears in each class by the average number for the class and adding the products gave a sum which tests have shown to closely approximate the actual number of average-size kernels destroyed per 100 ears. This sum, or injury index number, can be directly compared with that of another sample to 6how which is the more resistant. The injury index number varied slightly from one test to another within the same variety. Since some of the varieties listed in the tables were tested as many as eight times, the index number is not given. It was used, however, in compiling the tables, and the variety was listed as resistant, intermediate, or susceptible, with supplementary notes to denote the highly resistant strains. A strain was considered resistant or susceptible in our tests according to whether its injury index number fell below or above the median one-third for all strains in the test . - 3 - The factors responsible for resistance are not well understood. The tables show, however, that with few exceptions the degree of resistance found in a single cross is in proportion to that found in the inbred b. The plant breeder may be able to combine two or more of the known resist- ance factors to produce superior inbreds and hybrids. Many of the inbreds listed in table 1 have been tested in several crosses, so that we have some indication of their reaction in breeding. See tables 2 and 3. Where enough crosses have been tested, the reaction is shown in the "Remarks" column in the table. Many additional lines have been tested for ear-worm resistance but have been dropped from the breeding programs for various reasons. A few other lines that have been discarded by the originating breeders are listed in the tables, because they may still be under test by other breeders and cooperators. A few open -pollinated varieties and a few hybrids produced by commercial breeders were purchased in the open market and tested. These varieties are shown in table U» About 90 inbreds and hybrids of popcorn have been tested for earworm resistance. Consistent differences in the reaction to earworm injury have been noted in many of those tested, but so far none have shown a high degree of resistance. They are not listed in this paper. The reactions and resistance of sweet corn inbreds and hybrids to corn earworm injury follow. - 4 - Table 1. — Reaction to earworm injury and present status of sweet corn inbred s tested for resistance to the corn earworm. ■ Present Number of Tests Status Inbred^ Source and Resist- Inter- Suscept- 2/ Remarks^ Inbred Number , ant mediate ible Yellow Inbred i 9 Illinois 59» - 1 - D 60b - 1 ~ X 62a - - 1 s 64b - 1 - D 66a 3 - - X Breeds moderate resistance. t7a 1 - - D 68a 1 - - S Breeds susceptible. 70a 2 - - X 71a 2 - - RG Breeds moderate resistance. 72a 3 2 - E do. 72b - 1 - X Crosses test as other parent. 72c - 1 - X 73a - 1 - X 73c 1 2 ™ R Breeds moderate resistance. Used in Golden Hybrid No. 10. 74a - 1 - X 75a - 2 1 X 76a . 2 - Breeds moderate resistance. 76b - 1 - D 76d - 2 «■ X 78a 3 - - D Breeds intermediate. 80a 1 - D 80b 2 - - X do. 82a - 1 1 D 83a 1 1 1 D 84a 1 - ■■ D 85a 1 3 - X 85b 1 1 - X 85c - 1 - X Breeds susceptible. 85d 2 3 - X Breeds moderate resistance. 85e 1 1 D 86a - - 1 D Breeds susceptible. 86b - 1 - D 86c - 1 - X do. 86d a 2 - X Breads moderate resistance. 86a 1 1 - X do. 86f . 1 - D 87a - 3 - X Breeds susceptible. 87b - - 1 X 89a « 2 - R Breeds intermediate. 91a 2 - - X do. 92a - 1 1 X -5 - Table 1. — (Continued) Source and Inbred Number Number of Teste Resist- ant Inter- mediate Suscept- ible Present Status of Inbred^ Remarks Zl Illinois 93a 94a 95a 96a 97a 98a 98b 99b 101a 101b 101 c lOld 101a lOlf lOlh lOlj 1011 lOln lOlq 101r 101s lOlt lOlu 101t lOlw lOlx lOly lOlx alOl dlOl elOl flOl glOl 103a 103b 103c 103d 103e 103g 103h 103d Yellow Inbreds - 3 - D - - 2 D - 2 - D 2 1 - D - 1 - D 2 - - 5 1 • - E - 1 - D - 1 - E - mm 1 D - 1 - 1 - - E 1 1 - E - - 1 D - 1 - D . 1 - D - 1 - D - - 1 D - 2 - R „ 1 1 D - 1 - 4 4 - E 1 1 1 E - - 1 S - 2 - D - 2 - E 1 2 - D - 1 - E - 2 - E 2 - - E - 1 - E - - 1 E 2 1 - E 3 - - E l - - E - - 1 E - - 2 D l 1 - E l - - S - 1 - E - 1 m» S Breeds resistance. Breeds very susceptible. Breeds intermediate. do. Breeds moderate resistance. Used in Golden Hybrid No. 10. Breeds moderate resistance. Breeds intermediate. Breeds susceptible. Breeds intermediate to susceptible Breeds moderate resistance. - 6 - Table 1. — (Continued) Present Number of Tests Status of _, Inbred* Source and Resist- Inter- Suscept- R_*J/ Inbred Number ant mediate ible Yellow Inbred s Illinois 103k - - 1 I 1031 - 1 - S 103m - 1 - s 103n - 1 - s 104c - 1 - RC Breeds moderate resistance. 104d - - 1 S 104e - 1 - E 104f - - 1 D 104h - - 1 D 104J - - 1 E 104k - 1 - 8 1041 1 1 - S 104m - - 1 E 104q - 1 - s 105a - 1 - I 106a - 1 - s 106b . 1 - 8 107 a 3 1 S One of most resistant yellow inbreds. Crosses test as other parent. 107b - M 1 E 106a - - 1 D 108e - - 1 E 108f . - 1 E 108g - - 1 E 109a - 1 - E 110a - 1 1 E HOd - - 1 E HOf - 1 - D HOg - 1 - E HOh - - 1 E 110J - - 1 D Ilia - - 1 111b - 1 - D 112a - 2 - E 112b - 1 - E 112c - - 1 E 11 2d - 2 - E 112e 1 1 - E 112f mt 1 - S 112g - 1 - E 11 2h - 1 - E 112j - 1 - E - 7 - Table 1. — (Continued; Source and Inbred Number Number of Tests Resist- ant Inter- mediate Suscept- ible Present Status Inbred* Remarks 2/ Yellow Inbreds Illinois 113a 113b 113c 113d 113« 113f H3g 113h H3J 113k 1131 114a Indiana P14 33A-1 35(6)1 35(6)2 35B P39 P39A P39B P39C P39-10 P51 P51B 268 299 336 353 354 357 621 655 661 662 664 667 685 686 687 688 1 1 2 1 1 1 3 1 1 1 1 1 1 1 2 1 1 1 2 1 2 2 1 6 1 1 2 3 1 3 1 l l l l 2 1 1 1 1 1 1 1 1 1 S X X X D X s s s X X X R X RC RC X R R X R R R RC X X X X X X X X X X X X X X X Breed 8 susceptible. do. do. do. Early, diminutive P39 selection. Breeds susoeptible. Resistant to natural infestation only. Breeds susceptible, do. One of most resistant yellows. - 8 - Table l.~( Continued) Present Number of Tests Status of , Inbred- Souroe and Resist- 1 Inter- Suscept- Remarks-* Inbred Number ant | mediate ible Yellow Inbreds Indiana 695 - 1 - IE 703 - 1 - E 724 - - 1 S 1308 - 1 2 S 1 Breeds susceptible. 1313-1-1 - - 1 E 1313-1-2 3 - Mi S Lal(3)l - - 2 E Lal(3)3 2 - 1 E Lal(3)23 1 2 - E Lal(3)221 1 - 1 S La2(3)3 1 1 - E La2(3)H 1 1 1 E U2(3)21 2 1 - E La2(3)32 2 1 - E La2(3)52 - - 2 E Iowa IP39 - 3 - R Reacts similar to P39* 1*5 3 6 - R ] Breeds moderate resistance. 60 1 1 R ] Breeds susceptible. 467 - 3 - E ] Breeds resistance. 2019 . 1 1 R ] Breeds moderate resistance. 2021 - - 1 R 2052 - - 1 S 2067 - 1 - E 2174 l 1 - R Breeds resistance. Wx2l53-1 - 1 - E do. 2000 - am - S Highly resistant in 4 combination 2166A - - - R do. 5055 . - - E [intermediate in 3 combinations. 6014 . . - S Resistant in 2 combinations. 051K2A f\1_ - a, - - - S Resistant in 1 combination. Ohio S13 4 — _ RC Breeds resistance. 26 - 1 - S 28 1 - - S 29 - 2 - E 39KL 1 1 - D 39K3 - 1 - E 51KL - 2 1 RC 51K2-115 1 - - R Used in Ohiogold 1, 2, * 4. - 9 - Table 1. — (Continued) Number of Tests Source and Inbred Number Resist- ant Inter- Suscept- mediatej ible Present Status of Inbred Remarks i/ Is 3d 3f 3h 3J 3p 5a 5d 5J 5k 51 5* 5x b5 d5 g5 h5 J5 k5 15 6a 6h 6j 6k 61 6m 6n Yellow Inbreds Ohio 51K2-123 1 1 - S 51K2-Scharff 1 - - s S51 - 2 - s 52 - 1 - E 94b - - 1 S G192-74 - - 2 S BE&PQ La2W 4 2 Country Gentleman I E abrec Illinois If 3 • - R - 1 - R - 1 - R - 3 - R 1 - - R 1 - - R 2 1 - R „ 1 .. D 5 1 - R 1 2 _ S - 1 3 E - 2 - D 1 - - D - 1 1 D - - 1 E - 1 - S 2 - - S - 1 - D - 2 - E - 1 • E - 3 2 R 1 - - D 1 - - S 1 - - E - - 1 E - - 1 E — - 1 E Breeds resistance. Breeds intermediate. No longer used. Discarded. Breeds susceptible. No longer used. No longer used. No longer used. Discarded. do. No longer used. Very resistant. No longer used. Original release. Breeds intermediate. Present selection used in Illinois 5 x 10. Used in Illinois 5 x 10. - 10 - Table 1. — (Continued) Source and Inbred Number Number of Teste Resist- Inter- ant 1 mediate Present Status Suscept-j of ible I Inbred^, Remarks 2/ Country Gentleman Inbreds Illinois 8c 8d 8e 8f 8g 8h 8J 8k 81 8m 10a lOd lOe lOf 10g lOh 10j 101 lOn lOp lOq lOr 10s 15b 15h 18a 18b 19a 19b 20a 21a 21b 21c 21 e 22a 24a 24b 24c 24d 24e 1 1 4 1 1 1 1 1 2 1 1 1 2 3 2 1 1 3 l 2 1 1 1 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 3 l l 1 2 1 1 1 R Used in Illinois 8x6. Breedr> susceptible. E D D E E E Breeds susceptible. E E E R Original release. E D E E Breeds susceptible. E E D E E E R E D R E D D E E E E E D D E E Not used at present. Used in Illinois Hybrid No. 13 , - 11 - Table 1. — (Continued) Present Number of Tests Status Inbred^* Source and Resist- Inter- Suscept- Remarks-' Inbred Number ant mediate ible Country Gentleman Inbreds Illinois 27a 4 3 — R Breeds resistance. Used in Illinois Hybrids Nos. 13 & 14. 28a 1 2 - E 29a 2 - - D 31a " 5 *■ R Breeds intermediate. Used in Illinois Hybrid No. 14. 31b - l - E 32a - l - D 34a 1 2 - E 35a 2 1 - S 36b - - 2 E 38a - 1 - S 39a 3 - - E 41a - 1 - S 42a - 1 - E 43 a - 1 1 E 44b 2 3 - R Used in Illinois Hybrid No. 15. 45a - 6 - E 46b - 2 - E 46c - 1 - E 47a - 3 - R Used in Illinois Hybrid No. 15. 48a - 2 - E 48b - 2 - D 50a 1 1 - D 200d 1 3 - E 200f - - 2 E 200k 2 - - E Highly resistant. Breeds susceptible. Indiana FR1 • 2 - E FR14 1 - - S FR34 4 - - R Breeds moderate resistance. 10 - 1 - E 22-2 3 3 MB R do. 29 • l • E 30(17)1 - 2 - E 347 - 3 1 E Breeds very long ear. Some resistance. 348 - l 1 E 534 - l - E - 12 - Table 1. — (Continued) Source and Inbred Number Number of Tests Resist- ant Inter- mediate Suscept- ible Present Status ° f lil Inbred^* Remarks 2/ Country Gentleman Inbreds Indiana 732(5)KU 1 - E 6267 - - 1 E 6355 - 1 3 R 6532 2 - D 6609 - 1 E 6684 1 - D 7212 - 1 E 7685 1 1 D 7710 1 2 R 8035 1 - E 8065 2 - 1 D 8098 2 1 R 8111 - - 1 D 8203 - 1 2 R 8225 1 1 D 8339 - - 2 D 8344 4 - R Iowa 1445 2 - R 1627 - 1 R 2508 2 - R 2730 - 1 1 R 4011 2 - E 4024A 2 - E 4040 1 _ E 4060 - 1 E Evergreen Inbreds Illinois 11a - - 1 R lib - 1 E lie - 3 E lid - 3 R lie - - 1 E 13b - 3 S 13c - 1 R 13d - - 1 D Breeds susceptible. Breeds resistance. do. Highly resistant. Crosses test as other parent. Highly resistant. Crosses test as other parent. Original release, Used at present. - 13 - Table 1.— (Continued) Number of Tests Source and Inbred Number iumt 3 Resist -f Inter- ant J mediate Suscept- ible Present Status of Inbred^ Remarks 2/ Evergreen Inbreds Illinois 13h - 1 1 D 14a 1 1 - R 14b - 1 1 D 14d 1 2 - E 14g 1 - - R 14h - 1 - D 14k 1 IB - S 141 - 1 - D 14m - 1 - E 14n 4 - - E 14p 1 - - D 52a ■■ 2 - E 55a - 1 - R 55b - 1 - D 55c - 3 - D 55d - l - R 55* - l - E 57a - - 5 E 57b - - 5 E 58a - 2 - E Indiana 119 1 2 - E 65K3)1W - 1 - S 1009-8 - - l E 1014 - 2 - E 7600 - 2 - E 8449 1 2 - E Bl-1 - 1 l E Bl-21 - 1 l E Iowa 3001 - 2 - R 3002 - 2 - E 3005 1 1 - R 3006 - 2 - R 3044 - 1 MB E Ohio 22G 1 - 1 D 40 - - 1 E 42 - - 1 D 44 « 2 - E 45 1 2 - E AM-1-1-1 - - 2 E Original release. Used at present. Very resistant. Breeds resistance. Original release. - 14 - Table 1.— (Continued) Number of Teste Source and Inbred Number Resist- ant Inter- mediatel ible Suscep-L- Present Status of Inbredi Relics 8/ BPISAE-South Carolina 2d-2d-0d(Sel) 6 2d-2d-ld(Sel) 3 26-8-3-7a-l-l 26-8-3-7a-5-2 1 53-4a-l-l-2-2 2 80-ll-5b-5a-l-2b 1 81-1-3-3-2-11 6 BE&PQ & BPISAE (coop,) 241-U1-U3-U1-B 2 471-U6-A1-D2 5 471-U12-U3-B 471-U12-U5-B 3 Evergreen Inbreds S 8 S E D E S s E S s Very resistant. Breeds resistance. Breeds resistance. do. X/ Present status of the strain as given by the breeder. E - experimental, R - released to commercial trade, RC - release contemplated, D - discontinued or discarded by originating breeder, may still be carried by others. 2/ Remarks concerning resistance and breeding for resistance should be credited to the writer. 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Number of Tests Variety Resist- Inter- Suscept- ant mediate ible Aristogold Bantam 2 . Aristogold Bantam Evergreen 1 1 - Aunt Mary's Sweet - 2 2 Golden Grain - 1 mm Honey June - 2 - Hybrid St owe 11 • s - 1 - Mosshart Sugar 2 mm - Oregon Evergreen 2 2 - Papago Sweet 2 - - Stowell's Evergreen - - 1 Surecropper Sugar 1 1 - Sweet Snowflake - 1 1 Texas Evergreen 2 ■■ mm Top Flight Bantam - 2 - Tri State - 1 - US34 3 — ™