Virulence dynamics and phenotypic diversity of Puccinia coronata f.sp. avenae in Canada from 1974 to 1990

In the eastern region, frequency of virulence to Pc39 increased after the release of a cultivar with this resistance gene. Virulence to Pc38 and Pc39 increased in the prairie region after cultivars with these two genes were released. Frequencies of virulence to Pc35 and Pc56 fluctuated between 9-53% in the eastern region, even though these genes are not known to be present in oat cultivars grown there. In the prairie region, the frequencies of virulence to Pc35 and Pc40 fluctuate dbetween 21-60% from 1974-1990, and virulence to Pc46 increased from 7% in 1974 to 72% in 1985, even though these genes have not been used in commercial oat cultivars. The prairie population generally had higher levels of phenotypic diversity than did the eastern population in almost all years examined. -from Authors