Evaluation of the Potential Risk Posed by Emerging Yr5-Virulent and Predominant Races of Puccinia striiformis f. sp. tritici on Bread Wheat (Triticum aestivum L.) Varieties Grown in Türkiye

In this study, the reactions of 70 bread wheat varieties released in Türkiye to five prevalent <i>Pst</i> races, including the <i>Yr5</i>-virulent PSTr-27, were evaluated. Reaction tests of wheat varieties to all races revealed PSTr-27 as the most aggressive race, followed by PSTr-31, PSTr-28, PSTr-29, and PSTr-30. Notably, only seven varieties (Kıraç 66, İkizce 96, Dinç, Altındane, Ziyabey 98, Bayraktar 2000, and Shiro) exhibited moderately resistant reactions to PSTr-27, while the remaining varieties were susceptible. The presence of nine important resistance (<i>Yr</i>) genes in these varieties was also screened at the molecular level. <i>Yr5</i>, <i>Yr15</i>, and <i>Yr26</i> genes were not detected in any of the varieties and <i>Yr10</i> and <i>YrSP</i> genes were each detected in only one variety, while the other genes were detected in different ratios. Molecular screening showed that 19 varieties with no resistance genes used in this study displayed susceptible reactions; however, ten varieties that did not carry any resistance genes showed resistant reactions to one or more races, suggesting the presence of unknown or novel resistance sources. Furthermore, gene combinations, particularly <i>Yr10</i> + <i>Yr18</i>, significantly provided resistance to all <i>Pst</i> races studied. These findings highlight that continual monitoring of PSTr-27, and other <i>Pst</i> races is needed, since it can be a serious threat to wheat production in Türkiye and neighboring countries.