The genetics of seedling resistance to leaf rust,Puccinia hordeiOtth. in some spring barley cultivars

Summary The three Dutch isolates studied carried virulence genes against the resistance genes Pa, Pa-2, Pa-4 and Pa-5, substantiating the widespread occurrence of these virulences in Western Europe as reported by others. The cultivars Cebada Capa, La Estanzuela, Gondar and Dabat carry the same dominant to semi-dominant gene, which is also found in Forrajera Klein and H2212. It is proposed to designate this gene Pa-7. This gene segregated independently from the Pa-3 gene in Rika x (Baladi x Rika) substantiating the data of Johnson (1968), but disagreeing with those of Roane & Starling (1970). EP 75 seems to carry a single dominant or semi-dominant gene conferring an intermediate resistance to the isolates used. This gene, tentatively designated as Pa-z, is different from the Pa, Pa-2, Pa-4, Pa-5 and Pa-7 genes. The intermediate resistance of Monte Christo is probably based on gene(s) different from EP 75.