Heat tolerance is a physiologically and genetically complex trait regulated by multiple genes. To investigate the genetic basis of heat tolerance, eight parents (five lines and three testers) and their fifteen F1 hybrids were evaluated under normal and high-temperature stress conditions for two consecutive years. Data were recorded for plant height, number of bolls, boll weight, seed cotton yield, ginning out turn (GOT%), H₂O₂, catalase, peroxidase, super-oxidase dismutase, total soluble proteins, carotenoids, chlorophyll a & b contents, short fiber index, fiber strength, UHML, micronaire value, reflectance, and uniformity index. Line × tester analysis suggested that the contribution of lines was higher than testers. Non-additive gene action was observed for all studied traits. The variances of SCA were greater than GCA variances for all studied traits revealed that these traits were governed by a few largely dominant genes. Fb-Shaheen, Eagle-2 and JSQ White Gold were found good general combiner whereas the cross Fb-Shaheen × JSQ White Gold was a good specific combiner and revealed significant better parent heterosis for most of the traits during two years under normal and high temperature stress conditions. The information obtained could be utilized in a breeding program for the development of new synthetic varieties of heat tolerance.

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.