Inheritance of resistance to Pyrenophora teres f. teres in spring barley

The inheritance of seedling resistance to a Swedish isolate of Pyrenophora teres f. teres was investigated in four resistance sources of spring barley. Accessions CI 2330, CI 5791, CI 5822 and CI 9776 were used as resistance sources, and the cultivar 'Alexis' was used as a susceptible parent in different crosses. From the disease reaction in the F-1, F-2 and F-3 generations it was concluded that the resistance was governed by the same two complementary genes in CI 5791, CI 5822 and CI 9776. One of these genes was present in CI 2330. The first three cultivars were highly resistant to the isolate used in this investigation. These results, when combined with earlier studies, suggest that CI 5791, CI 5822 and CI 9776 may be of great value as sources of resistance to barley net blotch. Spearman's rank correlation between the disease reaction of F-2 plants and their F-3 progeny was highly significant (r = 0.75; P less than or equal to 0.001). It is suggested that selection in the F-2 generation is effective. In a backcross breeding scheme, single plant reactions in F-1 or F-2 need to be confirmed in later generations.