|Coe Jr, Edward|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/1997
Publication Date: N/A
Citation: Interpretive Summary: The corn earworm is a major insect pest of corn causing direct losses due to silk and kernel feeding and exposing ears to enhanced contamination by ear-rotting fungi. Previous studies have indicated that a chemical compound known as maysin, found in silks of specific corn varieties, may confer resistance to the corn earworm. We have previously identified the genes controlling the synthesis of maysin in a population derived from a cross between the corn inbred lines GT114 and GT119. In this study, we used a laboratory bioassay of corn earworm larvae feed on silks from this same population to show that the genes controlling the synthesis of maysin also control growth of the larvae. These results are significant in demonstrating that selection by corn breeders for the genes we identified as controlling maysin synthesis will result in the development of corn varieties with enhanced corn earworm resistance thereby reducing losses due to this pest.
Technical Abstract: A better understanding to the genetic basis of antibiosis to the corn earworm, Helicoverpa zea (Boddie), in maize, Zea mays L., silks will help breeders develop hybrids with improved resistance to this pest. The objective of our study was to identify maize chromosome regions associated with antibiosis to the corn earworm, and to compare the results with those previously obtained for concentration of silk maysin, a C-glycosyl flavone that inhibits larval growth. We evaluated antibiosis with a dried-silk bioassay of 76 (GT114 x GT119)F2:3 lines, derived by self-pollinating F2 plants from the high and low tails of the distribution for silk maysin concentration. Variation in 8-d larval weights resulting from silks of the F2:3 lines was compared with variation in restriction fragment length polymorphism genotypes at flavonoid pathway loci or linked markers of corresponding F2 plants. The multiple-locus model that best explained variation of larval weights included a major effect at the p1 region of chromosome 1 and smaller effects in the umc166b region (chromosome 1) and th she region (chromosome 9). The model for maysin concentration of the corresponding F2 plants was nearly identical, with the exception that the sh1 locus was replaced by the nearby umc105a locus. Our results provide evidence that in this population silk maysin concentration and corn earworm antibiosis are under similar genetic control and that the p1 locus plays the major role in determining variation in both traits.