Disease Severity and Grain Yield in Barley Multilines with Resistance to Powdery Mildew

Superiority of yield in cultivar mixtures may be ascribed to specific and nonspecific resistance against leaf pathogens and to differential reactions of components to environment. This study was conducted to investigate the significance of specific resistance on powdery mildew (Erysiphe graminis DC.: Fr. f. sp. hordei) severity and grain yield in barley (Hordeum vulgare L.) multilines and isolines, each carrying different genes for specific resistance to powdery mildew. Multilines were composed of equal proportions of four or five isolines. In the multilines, disease levels were 50 to 80% lower than the mean level for the components grown in pure stands. The advantage of mixing increased with increasing mean level of resistance in the component isolines. Grain yield in both multilines and isolines increased with the mean level of resistance, with most resistant multilines producing higher grain yields than predicted by the mean level of the components in pure stands. The results indicate that components with higher levels of resistance gained the most benefit from utilizing them in a multiline.