Comparison of silk maysin, antibiosis to corn earworm larvae (Lepidoptera: Noctuidae), and silk browning in crosses of dent x sweet corn

Sweet corn is one of the highest ranking vegetable crops in the United States 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. Plant resistance is an alternative strategy to alleviate environmental concern when pesticides are used. In this study we investigated the feasibility of transferring antibiosis to corn earworm, Helicoverpa zea (Boddie), from dent corn with high silk maysin to sweet corn. Relationships among silk maysin concentration, antibiosis to corn earworm, and silk browning in their F(2) segregating populations were determined. Lyophilized high maysin silks bioassays produced low larval weights, thus providing evidence that damage to sweet corn by corn earworm could be reduced by increasing silk maysin concentration. Simple correlation coefficients indicated a highly significant negative association between silk maysin concentrations and 8-d corn earworm larval weights (r approximately equal to -0.80, P < 0.0001). Silk browning was also closely associated with silk maysin concentrations and antibiosis. Diets containing 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 F(2) 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 in these populations may have a recessive gene, which may be closely linked to sh2 locus enhancing/regulating maysin synthesis when crossed to a maysin producing dent parent.