Inheritance of Resistance in Two Wheat Cultivars To an Australian Population of Heterodera a Venae

Resistance to H. avenae in Loros (AUS 90248) and Spring Wheat (AUS 10894) is due to the same single major dominant gene because progeny tested from the F2 of the cross between these cultivars reacted similarily to the two resistant parents. In crosses between resistant and susceptible cultivars, partial dominance of the resistance was indicated by the reactions of F1 progeny and although a bimodal distribution in the F2 generations was not obtained, an arbitrary numerical line of demarcation was used to determine the most likely hypothesis for the inheritance of resistance. This difficulty in determining genotypic reactions to H. avenae is discussed in relation to the effects of modifier genes in the host and aggressiveness of the nematode on the expression of resistance in cereals to H. avenae.