Sequence-tagged microsatellite profiling was used to develop 110 microsatellites for Puccinia graminis f. sp. tritici (causal agent of wheat stem rust). Low microsatellite polymorphism was exhibited among 10 pathogenically diverse P. graminis f. sp. tritici isolates collected from Australian cereal growing regions over a period of at least 70 years, with two polymorphic loci detected, each revealing two alleles. Limited cross-species amplification was observed for the wheat rust pathogens, P. triticina (leaf rust) and P. striiformis f. sp. tritici (stripe rust). However, very high transferability was revealed with P. graminis f. sp. avenae (causal agent of oat stem rust) isolates. A genetic diversity study of 47 P. graminis f. sp. avenae isolates collected from an Australia-wide survey in 1999, and a historical group of 16 isolates collected from Australian cereal growing regions from 1971 to 1996, revealed six polymorphic microsatellite loci with a total of 15 alleles. Genetic analysis revealed the presence of several clonal lineages and subpopulations in the pathogen population, and wide dispersal of identical races and genotypes throughout Australian cereal-growing regions. These findings demonstrated the dynamic population structure of this pathogen in Australia and concur with the patterns of diversity observed in pathogenicity studies.
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