Effects of induced resistance on infection efficiency and sporulation of Puccinia striiformis on seedlings in varietal mixtures and on field epidemics in pure stands

An inducer race of Puccinia striiformis inoculated two days before a challenger race on wheat seedlings of cv. Clement, reduced infection efficiency by 44% and lesion expansion by 7.7%; there was no effect on sporulation rate. In held epidemics, induced resistance restricted the disease intensity on cvs. Clement and Austerlitz in pure stands by 44% and 57% respectively. In the glasshouse at the seedling stage, disease intensity in a varietal mixture was reduced by 82% compared to the susceptible pure stands; one third of the total disease reduction was attributable to induced resistance.