MAIZE SILK MAYSIN CONCENTRATION AND CORN-EARWORM ANTIBIOSIS - QTLS AND GENETIC MECHANISMS

Growth of the corn earworm (Helicoverpa tea Boddie), a major pest of m aize (Zea mays L.), is inhibited by high concentrations of maysin, a C -glycosyl flavone, in maize silks. To advance understanding of the gen etic control of silk maysin concentration and antibiosis to corn earwo rm, we conducted a quantitative trait locus (QTL) study in a populatio n derived from a cross of high-maysin (GE37) and low-maysin (FF8) line s. Both lines have phenotypically identical, functional alleles at the pi. locus, a regulator of the biochemical pathway leading to maysin s ynthesis. We evaluated 250 (GE37 x FF8)F-23 families far (i) restricti on fragment length polymorphisms at 121 loci, (ii) silk maysin concent rations in two locations tin Georgia and Missouri), and (iii) weight o f corn earworm larvae grown on artificial diet containing oven dried s ilks. For maysin concentration in both locations, composite interval m apping revealed major QTLs in the asg20-whp1 interval of chromosome 2 and near the wx1 locus on chromosome 9; smaller effects were detected on chromosomes 1, 6, and 8. For larval weight, the largest QTL was det ected in the asg2O-whp1 interval, and major effects were also associat ed with chromosomes 1 and 6. However, we found no effect on larval wei ght at wx1. Significant (P < 0.001) epistasis was observed for all tra its. Our results suggest that whp1 on chromosome 2, a gene that encode s chalcone synthase and sm1, a silk-specific gene on chromosome 6, are candidate genes affecting maysin concentration and corn earworm larva l weight in this population.