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Global population genetics of the wheat leaf rust fungus Puccinia triticina
J. KOLMER (1), M. Ordonez (2). (1) USDA ARS, St Paul, MN, U.S.A.; (2) Pontifical University Catholica, Quito, Ecuador

Collections of <i>Puccinia triticina</i> were obtained from North America, South America, Central Asia, Europe, the Middle East, Russia and China to examine the genetic diversity within each continental region and genetic relationship between regions. Approximately 100 single uredinial isolates from each region were tested for virulence phenotype to 20 near-isogenic Thatcher wheat lines and for molecular genotype with 23 simple sequence repeat (SSR) primers. All continental populations had significantly higher than expected SSR allele heterozygosity and had very high (>3.00) index of association (IA) values, indicating clonal reproduction worldwide. Genetic differentiation for SSR genotype groups varied from 8 groups in Europe to 2 groups in Russia. In all regions <i>RST</i> differentiation was greater than <i>FST</i> indicating the likely importance of SSR mutation in generating variation. Within all populations <i>FST</i> and <i>RST</i> differentiation based on geographic regions was lower than differentiation based on SSR genotype groups, indicating the migration of SSR genotypes within continental regions. In all populations SSR genotypes were significantly correlated from 0.55 to 0.42 with virulence phenotypes. Grouping based on <i>FST</i> and <i>RST</i> in neighbor joining dendrograms of the worldwide SSR genotype groups had low correlation, however both measures separated groups of SSR genotypes that originated from durum wheat from collections from common wheat.

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