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ARS Home » Southeast Area » Tifton, Georgia » Crop Genetics and Breeding Research » Research » Publications at this Location » Publication #95345
Title: COMPARISON OF SILK MAYSIN, ANTIBIOSIS TO CORN EARWORM LARVAE (LEPIDOPTERA: NOCTUIDAE), AND SILK BROWNING IN SILKS OF DENT X SWEET CORN CROSSES

Author
item Guo, Baozhu
item Widstrom, Neil
item WISEMAN, B. - USDA-ARS, RETIRED
item SNOOK, M. - USDA-ARS, RETIRED
item Lynch, Robert
item PLAISTED, D. - NOVARTIS SEEDS, INC

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Sweet corn is one of the highest ranking vegetable crops in the U.S. in terms of both market value and total acreage; it also ranks among the top vegetable crops in terms of pesticide usage. Ear damage caused by insects is the most significant concern to producers. An estimated 25-40 insecticide applications may be made in a single season to control ear-feeding insects. Field corn lines with resistance to the corn earworm have been identified. The resistance is due to a chemical called "maysin" in the silks. In this study, we investigated the feasibility of transferring the resistance to corn earworm from field corn with high silk maysin to sweet corn. Laboratory silk bioassays showed that larvae which fed on silks with high maysin levels were much smaller, thus, providing evidence that damage to sweet corn by corn earworm could be reduced by increasing silk maysin concentration. At 8 days, larvae which fed on silks with the higher maysin concentration weighed the least. Silks with a high concentration of maysin turned brown when they were cut. Silks that turned dark brown reduced larval weight by an average 85%, and silks which turned moderately brown reduced larval weights by 68% compared with weights (588 mg) of larvae on the control diet. Sweet corn in F2 population of the cross was also noted to have high levels of maysin, if maysin was present, indicating that a maysin enhancing gene may be associated with the sh2 gene which provides sweetness in sweet corn. Results of this study suggest that transferring resistance due to maysin may be an alternate strategy for control of corn earworm damage in sweet corn without the extensive use of pesticide.

Technical Abstract: Sweet corn is one of the highest ranking vegetable crops in the U.S. in terms of both market value and total acreage; it also ranks among the top vegetable crops in terms of pesticide usage. Ear damage caused by insects is the most significant concern to producers. An estimated 25-40 insecticide applications may be made in a single season to control insects. Genetic control is an alternative strategy to alleviate environmental concern. In this study, we investigated the feasibility of transferring antibiosis to corn earworm from high silk maysin dent corn to sweet corn and determined relationships among silk maysin concentration, antibiosis to corn earworm, and silk browning in their F2 segregating populations. Dry-silk bioassays produced low larval weights as a result of the high maysin concentrations in silks, thus providing evidence that damage to sweet corn by corn earworm could be reduced by increasing silk maysin concentration. Correlation coefficients suggested a highly significant negative association between silk maysin concentrations and 8-d corn earworm larval weights. Silk browning was also closely associated with silk maysin concentrations and antibiosis. The dark color silks reduced larval weight by an average 85% and mid-dark silks reduced larval weights by 68% compared with larval weights (588 mg) on the bean diet control. Maysin analyses and dry-silk bioassays also revealed that if maysin is present in F2 plants from sweet corn kernels, it is always in a higher concentration than in plants from dent kernels. These results suggest that sweet corn parents may have a recessive gene which may be closely linked to sh2 locus enhancing/regulating maysin synthesis.