Plant Genome III Conference Plant Genome III Conference
Antibiotic resistance to the cam earworm (GEW), Helicoverpa zea (Boddie), in maize, Zea mays L, is due primarily to the silk content of maysin and related flavone glycosides synthesized as part of the flavonoid metabolic pathway. Our study sought to determine the genetic factors controlling maysin synthesis in the population (GTl 14 x GTl 19)F2, derived from a cross of a high-by a low-maysin parent. Silk maysin concentrations and RFLP genotypes at loci encoding flavonoid pathway enzymes or linked marker loci were determined for 285 F2 plants. Single-factor analysis of variance showed that 57.4% of the variance in maysin concentration was accounted for by the pl locus (region), which showed nearly completely additive gene action. An additional 5.2% of the variance was accounted for by the region on Chromosome 9 containing the loci cl and bzl, with the segment from the low-maysin parent contributing to higher maysin values. Two- and three-way interactions among pl, rl, and the cl-bzl region (significant at P< 0.01) provided evidence for the complex interplay of the pl-controlled and rl,cl-controlled portions of the pathway in the expression of this trait. In future research, we will focus attention on identifying additional loci affecting maysin synthesis. This project relates a quantitative traft to a defined genetic and biochemical pathway and serves as a model for understanding variation in other quantitative traits.