The biological basis of epistasis between quantitative trait loci for flavone and 3-deoxyanthocyanin synthesis in maize (Zea mays L.)

A major weakness in our understanding of the genetic basis of complex trait s has been that of defining the extent and biological basis of epistasis. O ur research group has been studying the genetic control of the accumulation of maysin, a C-glycosyl flavone, in maize, Zea mays (L.), silks. Previousl y, we demonstrated the importance of the p1 locus as a QTL for maysin synth esis. The p1 locus often exhibits significant epistatic interactions with o ther loci. We developed a mapping population, (W23a1 x GT119)F-2, specifica lly designed to test whether genes in an intersecting pathway might be dete cted as QTLs for maysin synthesis and result in epistatic interaction effec ts. The a1 gene is not required for the synthesis of flavones but is requir ed for the synthesis of 3-deoxyanthocyanins, an intersecting pathway, in ma ize silks. The p1 locus (P < 0.0001) was a QTL for both flavones and 3-deox yanthocyanins. The a1 locus was also highly significant (P < 0.0001) for bo th traits, as was the p1 x a1 epistatic interaction (P < 0.0001). Our resul ts demonstrate that altering the flux of biochemical intermediates between pathways may be the biological basis of major QTL effects and epistatic int eractions.