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 diff erent crosses. From the disease reaction in the F-1, F-2 and F-3 generation s it was concluded that the resistance was governed by the same two complem entary genes in CI 5791, CI 5822 and CI 9776. One of these genes was presen t in CI 2330. The first three cultivars were highly resistant to the isolat e used in this investigation. These results, when combined with earlier stu dies, suggest that CI 5791, CI 5822 and CI 9776 may be of great value as so urces of resistance to barley net blotch. Spearman's rank correlation betwe en the disease reaction of F-2 plants and their F-3 progeny was highly sign ificant (r = 0.75; P less than or equal to 0.001). It is suggested that sel ection 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 generati ons.