Wheat stripe rust, caused by a biotrophic, obligate fungus Puccinia striiformis f. sp. tritici (Pst), is a destructive wheat fungal disease that exists worldwide and caused huge yield reductions during pandemic years. Low temperatures favor the development of the disease, but the global average temperature has been increasing since 1850, especially in China, which has a higher rising rate than the global average. In the last two decades, Pst isolates have shown increased aggressiveness under high temperatures. However, the effect of rising temperatures on the aggressiveness of Pst has remained unknown in China. Therefore, this study assessed the aggressiveness of 15 representative Pst isolates (6 new isolates collected before 2016 and 9 old isolates collected after 2016) in Gansu under high temperatures by measuring and comparing disease severity, spore germination, and latent period on wheat seedlings at 16 °C, 18 °C, and 22 °C. The results indicated that the six new isolates showed greater disease severity, higher spore germination ratio, and shorter latent period than the nine old isolates, indicating that the new isolates were more aggressive under high temperatures than the old isolates. Some new isolates, such as CYR34, CYR33, and CYR32, which are predominant, were inferred to be associated with high-temperature adaptation in addition to having more susceptible hosts. Our results provided an insight into changes in Pst isolates at warmer temperatures and increasing incidence of wheat stripe rust in China, especially in eastern sporadic epidemiological areas in recent years. Thus, the new isolates are likely to be a potential risk for causing increasing stripe rust incidence.

Wheat Stripe rust, caused by Puccinia striiformis f. sp. tritici ( Pst ), poses a significant threat to wheat production globally. Understanding regional virulence patterns is crucial for effective resistance gene deployment and sustainable disease management. A total of 209 Pst isolates were collected from six provinces (Gansu, Qinghai, Shaanxi, Hubei, Henan, and Jiangsu) across two major epidemic regions in 2023–2024. Isolates were tested against 19 Chinese differential hosts and 18 Yr single-gene differentials. Using Chinese differentials, 54 races were identified, with CYR34 (19.62%), CYR32 (10.53%), and CYR33 (9.09%) being predominant; 31 were new. The Yr single-gene differential detected 63 races, VR1 (10.05%), VR2 (6.22%), and VR3 (5.74%) were the most frequent in the VR (Virulence Race) system, where numbers indicate sequential race designations based on distinct virulence patterns. Virulence assessment showed overwhelming prevalence against 17 Chinese varieties and 10 single-gene lines (> 60% frequency), while complete susceptibility absence occurred against Zhong 4 ( Yr genes unknown), Triticum spelta Album ( Yr5 ), Avocet S*6/ Yr5 , and Avocet S*6/ Yr15 . This study validates the superior discriminatory power of Yr single-gene differentials for Pst race identification and provides essential baseline data for regional resistance breeding programs. The findings support the adoption of enhanced surveillance systems for sustainable stripe rust management in China.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), threatens global wheat production. In China, wheat stripe rust generally occurs in northwest and southwest epidemic regions; still, the genetic relationship of Pst populations between these regions is largely unclear. We characterized the virulence structure, genetic diversity, and migration routes by analyzing 202 Pst isolates from the southwestern provinces of Guizhou (GZ), Sichuan (SC), and northwestern provinces of Shaanxi (SX), Gansu (GS), Xinjiang (XJ) during 2023. Isolates were phenotyped on 21 Chinese differential hosts, 20 monogenic lines, and genotyped using 22 KASP-SNP markers. Phenotype tests showed CYR34 (7.92%), and G22-316 (6.44%) were the predominant races with different occurrence frequencies in different regions. Virulence analysis showed that all isolates remained avirulent to Yr5 and Yr15, while virulence to Yr10, Yr1, Yr9 was generally below 40%. In contrast, high virulence frequencies (>80%) were observed against Yr6, Yr7, Yr17, Yr18, Yr32, Yr43, Yr44, YrTr1, and YrExp2 in multiple regional populations. Genotypic analysis revealed that a total of 156 multilocus genotypes (MLGs) were identified, and genotypic diversity in the XJ population was the highest, but limited gene flow (Nm < 1) with other populations. SC may serve as a bridge connecting Pst populations of southwestern (SC and GZ) and the northwestern (SX, GS, and XJ) provinces, showing frequent gene exchange (Nm > 4) occurred with other populations. These findings enhance the understanding of regional differentiation and diversification of Pst in southwest and northwest in China.