Identification of maize chromosome regions associated with antibiosis to corn earworm (Lepidoptera: Noctuidae) larvae

A better understanding of the genetic basis of antibiosis to the corn earworm, Helicoverpa tea (Boddie), in maize, Zea mays L., silks will help breeders develop hybrids with improved resistance to this pest. We identified maize chromosome regions associated with antibiosis to the corn earworm, and compared 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)F-2:3 lines, derived by self-pollinating Fz 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 F-2:3 lines was compared with variation in restriction fragment length polymorphism genotypes at 39 flavonoid pathway loci or linked markers of corresponding F-2 plants. The multiple-locus model that best explained variation of larval weights included a major effect at the pi region of chromosome I and smaller effects in the umc166b region (chromosome 1) and the sh1 region (chromosome 9). The model for maysin concentration of the corresponding F-2 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 pi locus plays the major role in determining variation in both traits. Because we evaluated the tails of the distribution and probed only at flavonoid pathway loci, all chromosome regions associated with corn earworm resistance in this population may not have been detected.