Genotypic variation in Rhynchosporium secalis pathotypes collected in the Western Cape Province of South Africa

An anonymous multilocus DNA probe was used to characterize the genotypic structure of Rhynchosporium secalis isolates previously characterized according to their virulence spectra on a set of differential barley cultivars. The maximum percentage of genotypic diversity of 47 R. secalis isolates from the Western Cape Province of South Africa was 46.5%. In comparison with diversity observed at DNA level, less variation was observed in pathogenicity for R. secalis. DNA polymorphisms in R. secalis seemed to be independent of variation in virulence. No correlation between any particular fingerprint pattern, race, district, field or lesion was observed. The two most frequently observed races, 4 and 7, did not share the same genotypes, even when isolated from the same field or lesion. The high level of genotypic variation observed in the South African R. secalis population resembles the genotypic diversity observed in other cereal pathotypes with known sexual states. Although no teleomorph has yet been observed, these data suggest that sexual recombination may operate within the South African population of R. secalis.