Effectiveness of incomplete resistance to Pyrenophora tritici-repentis in wheat

Abstract

Severe epidemics of yellow spot (Pyrenophora tritici-repentis) reduced grain yield by c. 60% in the highly susceptible wheat cv. Banks in two experiments. About two-thirds of the yield loss was associated with reduced grain size. Milder epidemics developed in cultivars with incomplete resistance and resulted in substantially smaller effects on grain yield. The value of the resistance in a high-yielding background was illustrated by yield advantages over Banks of c. 230% for Genaro 8 1 and c. 190% for Vicam 7 1, under heavy disease pressure. Lines selected from crosses of Genaro 81/2*Banks and Vicam 7!/2*Banks had less disease than Banks and only small to moderate yield losses occurred in the best selections under heavy disease pressure. This illustrates that the resistance from these sources can be transferred readily into adapted Australian wheats and should greatly reduce yield losses from yellow spot.