Population composition and virulence of Puccinia striiformis f. sp. tritici in Kazakhstan

In recent years, epidemics of wheat yellow rust caused by <i>Puccinia striiformis</i> f. sp. tritici (<i>Pst</i>) have been observed in major winter wheat-producing regions in Kazakhstan. However, there is currently very little information about the racial composition and virulence of <i>Pst</i>. The global emergence of aggressive and genetically diverse <i>Pst</i> races leads to different seasonal and geographic patterns of the pathogen, making cultivated wheat varieties vulnerable to the pathogen and potentially causing yellow rust epidemics. Three periods with different characteristic dominant <i>Pst </i>races were distinguished in Kazakhstan during 1985–2022. The first period covers 1985–2000, when in the southeast of the country, the main <i>Pst</i> races were 7E156 (31/1.5), 7E158 (A-8/5), 39E158 (X/1.5) and 86E16. In the second period (2001–2010), the crops were dominated by races 7E159, 31E159 and 47E224, which showed virulence to varieties with resistance genes Yr9 and Yr18. In the third period (2018–2022), the most dominant races in the fungal population were 7E159, 39E158, 79E73, 79E179, and 111E158, exhibiting virulence to varieties with the Yr26 and Yr27 genes. In the background of field infection, the resistance genes Yr5, Yr10, and Yr15 remain reliable in ensuring resistance; the Yr4, YrSp, and YrND sources are also highly effective against the <i>Pst</i> population.