Expression of adult plant resistance and its effect on the development of Puccinia striiformis f.sp. tritici in some Australian wheat cultivars

The onset of adult plant resistance (APR) to Puccinia striiformis was examined in seven Australian wheat cultivars under field conditions and in 14 cultivars under controlled environmental conditions. In most cultivars under field conditions the percentage leaf area affected by stripe rust at mid-tillering (GS 22–26; third leaf) was significantly less ( P < 0.05) than on the more susceptible cultivar Teal. The expression of APR was more conspicuous during tillering to node formation; at these growth stages chlorosis and/or necrosis developed in association with rust colonies on the most resistant cultivars. Under controlled conditions, the primary leaves of all cultivars except Olympic and Flinders displayed some resistance when compared with Teal (lower infection types, longer latent periods and/or less percentage leaf area affected). Studies on the spread of stripe rust from infection foci established in selected cultivars in the field indicated that the resistance detected at early growth stages in Suneca in controlled environmental studies also appeared to be effective in the field.