Abstract
Records from seven spring wheats in a diallel cross showed that flag-leaf lamina area, extrusion of the head from the leaf sheath, head length and yield were all controlled by minor genes. Additive gene action and general combining ability were shown to be important genetic factors for all characters studied. Partial dominance was present for yield, flag-leaf area and head length. There was evidence that over-dominance played a part in the inheritance of extrusion. The genetic factors which controlled the expression of small leaf size showed dominance over those for large leaves and appeared to be distributed over all chromosomes. Increased extrusion and large flag-leaf area were both shown to be associated with high yield.