Isozyme uniformity and virulence variation in puccinia graminis f. sp. tritici and p. recondita f. sp. tritici in australia

Abstract

During a routine survey of pathotypes of Puccinia graminis f. sp. tritici (the wheat stem rust pathogen) and P. recondita f. sp. tritici (the wheat leaf rust pathogen) present in Australia during the 1981-82 growing season, 16 pathotypes of P. graminis tritici and 12 pathotypes of P. recondita tritici were detected in total samples of 193 and 180 isolates of the two pathogens respectively. For both pathogens the distribution of isolates amongst the different pathotypes was highly uneven. The commonest pathotype of P. graminis tritici (pathotype 343-1, 2, 3, 5, 6) comprised 50% of isolates while the commonest pathotype of P. recondita tritici (pathotype 104-2, 3, 6) made up 69 % of isolates. Many pathotypes of both species were represented by single isolates only. Large subsamples of these field-collected isolates (58 isolates of J'. graminis tritici representing seven pathotypes and 66 of P. recondita tritici representing six pathotypes) were randomly selected and used to assess isozyme variation in extant Australian populations of these two pathogens. No variation was detected within either pathogen species in the isozyme phenotypes of 11 different enzyme systems. These data are compared and contrasted with published data on patterns of variation at avirulence/virulence and isozyme loci in these species. © 1983 ASEG.