THE OAT LINE PC54 AS A SOURCE OF RESISTANCE TO CROWN RUST, STEM RUST AND POWDERY MILDEW IN EUROPE

The oat line Pc54 was found to be resistant to powdery mildew under bo th field and glasshouse conditions. The ratio of resistant to suscepti ble F-2 and F-2 progeny of a cross between a selection from the Pc54 l ine (Cc7422) and a susceptible cultivar (Selma) showed that, in additi on to carrying the crown rust resistance gene Pc54 and the Pg15 gene f or stem rust resistance, the mildew resistance of the Pc54 line was co nditioned by a single incompletely dominant gene along with additional factors which modified the expression of resistance. Previous results , that there was no linkage between genes Pc54 and Pg15, were confirme d. In addition, there was no evidence of linkage between the mildew re sistance gene and gene Pc54. Evaluation of selections from within the Pc54 line showed that the expression of both stem rust and mildew resi stance was modified by, or linked to, plant height. The effectiveness of genes Pc54 and Pg15, as measured by virulence frequencies, in centr al and eastern Europe is described.