Virulence phenotypes of<i>Puccinia striiformis</i>in Alberta from 2009–2011

Abstract One hundred and four isolates of Puccinia striiformis were obtained primarily from central Alberta during 2009–2011 from wheat, barley, foxtail barley and triticale. Isolates were identified as P. striiformis f. sp. tritici (Pst) or P. striiformis f. sp. hordei (Psh) based on virulence on differential seedlings. Twenty-five wheat differentials separated 67 Pst isolates into 12 pathotypes, with a single pathotype representing 48% of Pst isolates. Wheat differentials with resistance genes Yr5 and Yr15 were resistant to all 12 pathotypes, while wheat lines with genes Yr1, Yr10, Yr24, Yr28, YrTyee and YrSP were resistant to 80–98% of the isolates. The remainder of the wheat differentials were susceptible to all Pst isolates. Within the 37 Psh isolates, 12 pathotypes were detected based on 12 barley differentials, half of which were previously unreported in Alberta. The two most common Psh pathotypes combined accounted for 46% of the isolates. One half of the Psh isolates may be the result of hybridization between the two formae speciales since they exhibited virulence on a large number of wheat and triticale lines in addition to barley lines. Psh isolates with these virulence factors were more frequently recovered from six-row than two-row barley. For both formae speciales, there was no apparent association between pathotype and location, with pathotypes being widespread and recovered from multiple locations.

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