Race composition and pathogenicity associations of Rhynchosporium secalis in California

Data from a pathogenicity study involving 723 isolates of Rhynchosporium secalis, the causal agent of barley scald, were analyzed for race composition and pathogenicity associations. Isolates were collected from California in 1973, 1983, and 1984. The results showed that the collection made in 1973 differed drastically in race composition from the collections of 1983 and 1984. The 1973 collection was composed mostly of simple races that were capable of producing disease on a few host differentials. The two later collections contained large proportions of complex races that were pathogenic on a large number of differentials (...)