Wheat stripe rust (yellow rust [Yr]), caused by Puccinia striiformis f. sp. tritici, is an economically important disease of wheat worldwide. Virulence information on P. striiformis f. sp. tritici populations is important to implement effective disease control with resistant cultivars. In total, 235 P. striiformis f. sp. tritici isolates from Algeria, Australia, Canada, Chile, China, Hungary, Kenya, Nepal, Pakistan, Russia, Spain, Turkey, and Uzbekistan were tested on 20 single Yr-gene lines and the 20 wheat genotypes that are used to differentiate P. striiformis f. sp. tritici races in the United States. The 235 isolates were identified as 129 virulence patterns on the single-gene lines and 169 virulence patterns on the U.S. differentials. Virulences to YrA, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, YrUkn, Yr28, Yr31, YrExp2, Lemhi (Yr21), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), Fielder (Yr6, Yr20), Tyee (YrTye), Tres (YrTr1, YrTr2), Express (YrExp1, YrExp2), Clement (Yr9, YrCle), and Compair (Yr8, Yr19) were detected in all countries. At least 80% of the isolates were virulent on YrA, Yr2, Yr6, Yr7, Yr8, Yr17, YrUkn, Yr31, YrExp2, Yr21, Stephens (Yr3a, YrS, YrSte), Lee (Yr7, Yr22, Yr23), and Fielder (Yr6, Yr20). Virulences to Yr1, Yr9, Yr25, Yr27, Yr28, Heines VII (Yr2, YrHVII), Paha (YrPa1, YrPa2, YrPa3), Druchamp (Yr3a, YrD, YrDru), Produra (YrPr1, YrPr2), Yamhill (Yr2, Yr4a, YrYam), Tyee (YrTye), Tres (YrTr1, YrTr2), Hyak (Yr17, YrTye), Express (YrExp1, YrExp2), Clement (Yr9, YrCle), and Compair (Yr8, Yr19) were moderately frequent (>20 to <80%). Virulence to Yr10, Yr24, Yr32, YrSP, and Moro (Yr10, YrMor) was low (≤20%). Virulence to Moro was absent in Algeria, Australia, Canada, Kenya, Russia, Spain, Turkey, and China, but 5% of the Chinese isolates were virulent to Yr10. None of the isolates from Algeria, Canada, China, Kenya, Russia, and Spain was virulent to Yr24; none of the isolates from Algeria, Australia, Canada, Nepal, Russia, and Spain was virulent to Yr32; none of the isolates from Australia, Canada, Chile, Hungary, Kenya, Kenya, Nepal, Pakistan, Russia, and Spain was virulent to YrSP; and none of the isolates from any country was virulent to Yr5 and Yr15. Although the frequencies of virulence factors were different, most of the P. striiformis f. sp. tritici isolates from these countries shared common virulence factors. The virulences and their frequencies and distributions should be useful in breeding stripe-rust-resistant wheat cultivars and understanding the pathogen migration and evolution.

No abstract

No abstract

No abstract

Leaf samples with scald symptoms were taken from various barley cultivars in 1997 and 1998 at nine locations in Alberta for examination of pathogenic variability. Two hundred and fifty-six single-spore isolates of Rhynchosporium secalis were differentiated into 52 pathotypes using 12 differentials, which consisted of seven accessions with major resistance genes and five commercial cultivars. Fifty-two percent of isolates were virulent on cv. Harrington only (pathotype 1); five pathotypes, consisting of close to 25% of isolates, were virulent only on 4 of 5 commercial cultivars; and about 45 pathotypes, consisting of about 25% of isolates, were virulent on commercial cultivars and accessions. No differential was resistant to all pathotypes, and many pathotypes were represented by single isolates. There was a difference in pathotype diversity and complexity among locations in Alberta. Calmar, Lacombe, and Edmonton sites comprised the greatest number of pathotypes that were virulent on up to seven differentials; at the Beaverlodge, Carstairs, Stettler, and Westlock sites, pathotype 1 comprised more than 60% of total isolates with a few other pathotypes. The Trochu and Vegreville sites were intermediate in the number of pathotypes. Discriminant analysis based on the reactions of the 12 differentials also showed divergence in R. secalis virulence among locations. Pathogenic variability associated with location in Alberta is important in the context of breeding for resistance and use of the most resistant cultivars by producers.Résumé : En 1997 et 1998 en Alberta, des échantillons de feuille avec des symptômes de rhynchosporiose furent récoltés sur divers cultivars d'orge à neuf endroits en vue d'examiner la variabilité pathogène. Deux cent cinquante-six isolats monosporiques du Rhynchosporium secalis furent différenciés en 52 pathotypes à l'aide de 12 populations différentielles, dont sept obtentions possédant des gènes de résistance majeurs et cinq cultivars commerciaux. Cinquante-deux pour cent des isolats étaient virulents seulement sur le cv. Harrington (pathotype 1); cinq pathotypes englobant presque 25% des isolats étaient virulents seulement sur 4 des 5 cultivars commerciaux et environ 45 pathotypes englobant environ 25% des isolats étaient virulents sur les cultivars commerciaux et sur les obtentions. Aucune des plantes différentielles n'étaient résistante à tous les pathotypes et plusieurs pathotypes étaient représentés par des isolats uniques. Il y avait une différence dans la diversité et la complexité des pathotypes entre les emplacements en Alberta. Les sites de Calmar, de Lacombe et d'Edmonton comprenaient le plus grand nombre de pathotypes virulents sur jusqu'à sept populations différentielles ; aux sites de Beaverlodge, de Carstairs, de Stettler et de Westlock, le pathotype 1 comprenait jusqu'à plus de 60% du total des isolats et incluait seulement quelques autres pathotypes. Les sites de Trochu et de Vegreville étaient intermédiaires quant au nombre de pathotypes. Une analyse discriminante basée sur l...