GENETIC MECHANISMS UNDERLYING APIMAYSIN AND MAYSIN SYNTHESIS AND CORN-EARWORM ANTIBIOSIS IN MAIZE (ZEA-MAYS L.)

C-glycosyl flavones in maize silks confer resistance (i.e., antibiosis ) to corn earworm (Helicoverpa tea [Boddie]) larvae and are distinguis hed iv their B-ring substitutions, with maysin and apimaysin being the di-and monohydroxy B-ring forms, respectively. Herein, we examine the genetic mechanisms underlying the synthesis of maysin and apimaysin a nd the corresponding effects on corn earworm larval growth. Using an F -2 population, we found a quantitative trait locus (QTL), rem1, which accounted for 55.3% of the phenotypic variance for maysin, and a QTL, pr1, which explained 64.7% of the phenotypic variance for apimaysin. T he maysin QTL did not affect apimaysin synthesis, and the apimaysin QT L did not affect maysin synthesis, suggesting that the synthesis of th ese closely related compounds occurs independently. The two QTLs, rem1 and pr1, were involved in a significant epistatic interaction for tot al flavones, suggesting that a ceiling exists governing the total poss ible amount of C-glycosyl flavone. The maysin and apimaysin QTLs were significant QTLs for corn earworm antibiosis, accounting for 14.1% (re m1) and 14.7% (pr1) of the phenotypic variation. An additional QTL, re presented by umc85 on the short arm of chromosome 6, affected antibios is (R-2 = 15.2%), but did not affect the synthesis of the C-glycosyl f lavones.