GENETIC ARCHITECTURE OF GRAIN-YIELD IN DURUM-WHEAT UNDER DIFFERENT ENVIRONMENTS

Twelve basic generations, namely, P-1, P-2, F-1, F-2, B-1, B-2, B-1s, B-2s, B-11, B-12, B-21, and B-22 of three crosses involving six divers e cultivars of drum wheat were studied under normal and sown condition s to understand the nature of gene effects for grain yield. The 10-par ameter model was adequate in most of the cases to account for the vari ability in generation means under both the environments. Of the epista tic effects, trigenic interactions were invariably more important than other effects in the genetic control of yielding ability in wheat. Ad ditive X additive X dominance (x) and dominance X dominance X dominanc e (z) epistatic effects were contributed maximum than other effects to wards significant heterosis. The non-allelic interactions particularly at three gene level were predominant for this trait. Thus, a breeding method that can mop-up the genes to form superior gene constellations interacting in a favourable manner would be more suitable to accelera te the pace of its genetic improvement.