Virulence Characterization of Puccinia striiformis f. sp. tritici in China Using the Chinese and Yr single-gene Differentials

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat. Identifying Pst races is essential for developing resistant cultivars and managing the disease. In this study, 608 isolates collected from China in 2021 were tested with the Chinese set of 19 wheat variety differentials and the set of 18 Yr single-gene differentials. Of the 119 races detected with the Chinese set of differentials, 94 were new. A higher number (149) of races were identified using the Yr single-gene differentials. The frequencies of virulence factors to 17 of the 19 Chinese differential varieties and to 10 of the 18 Yr single-gene differentials were high (> 60%). None of the isolates were virulent to differentials Zhong 4 (Yr genes unknown) and Triticum spelta Album (Yr5) in the Chinese set and the Yr5 and Yr15 lines in the single-gene set of differentials, indicating that these genes or varieties are effective against the Pst population detected in 2021. Using the Nei’s genetic distance, the 16 provincial Pst populations were clustered into 6 groups based on the Chinese set and 8 groups based on the Yr single-gene set of differentials. In addition, we found that same races identified using the Chinese differentials could be further differentiated into different races using the Yr single-gene differentials, suggesting a higher differential capability than the Chinese set of differentials. The results provide a scientific basis for monitoring Pst populations and guiding resistance breeding in China.