Puccinia striiformis f. sp. tritici is the causal agent of wheat yellow rust with records of regular and severe epidemics in China. This study explored the population dynamics of the yellow rust pathogen in Gangu, northwestern China. In Gangu, the Weihe River runs from west to east and divides Gangu into three regions: North and South mountain, with the valley in between. To study the genetic structure of the pathogen in local populations, samples were collected over 3 years from the three regions at different altitudes both within and between the wheat cropping seasons. A total of 811 P. striiformis f. sp. tritici isolates were successfully genotyped using 16 simple sequence repeat markers. The results suggest that P. striiformis f. sp. tritici can survive year-round in Gangu. The P. striiformis f. sp. tritici populations migrated among the regions, and the migration pattern was not related to altitude. The oversummering populations in the North and South mountain regions were genetically different from each other; and the P. striiformis f. sp. tritici populations collected from the lower altitude in the valley had no relationship with any of the populations collected in the spring or fall, indicating that they too have a different origin. Signatures of random mating were found in the populations collected in both North and South mountain regions, but not in the valley populations.

Wheat yellow rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most important wind-borne diseases in all wheat-growing regions, and its occurrence can lead to devastating yield losses in wheat. In China, the wheat fields in Gansu act as an inoculum reservoir during summer periods and provide PST spores for wheat in the fall. The wheat fields in Qinghai provide large amounts of oversummering inocula. The exchange and migration of spores between the two regions are essential to ensure the persistence of PST. To confirm this relationship, we studied the genetic diversity, seasonal population dynamics, role of recombination, and gene flow between PST populations in different oversummering areas of Gansu and Qinghai using molecular markers combined with a spatiotemporal sampling strategy. Shared genotypes provide molecular evidence of migration between the pathogen populations in the two regions. The distribution of genotypic frequencies indicates that the pathogen mainly flows from Qinghai to Gansu in the autumn, whereas the opposite direction of movement occurs in the spring. The inoculum source from spring wheat can be directly transmitted to autumn seedlings, not necessarily through volunteer wheat. Therefore, the bridging effect of spring wheat may play a more important role than the off-season pathogen surviving on volunteer wheat plants. Furthermore, linkage disequilibrium tests indicate that sexual recombination continues throughout the year in the Tianshui and Dingxi regions of Gansu.

Nitrogen deficiency limits oat growth and productivity, but the molecular basis of contrasting low-nitrogen responses among oat germplasms remains poorly understood. This study compared the low-nitrogen-tolerant germplasm Jiayan No.2 with the low-nitrogen-sensitive germplasm ZNY256 after 15 days of hydroponic cultivation under normal nitrogen (10 mM NH₄NO₃) or low nitrogen (1.25 mM NH₄NO₃). Growth traits, plant nitrogen content, nitrogen-metabolism-related enzyme activities, soluble sugar content, transcriptomes, and untargeted metabolomes were analyzed. Low nitrogen reduced plant height and plant nitrogen content in both germplasms, with more pronounced changes in ZNY256. Root length was unaffected, whereas root dry weight decreased only in ZNY256. ZNY256 also showed a larger transcriptional response than Jiayan No.2. Functional analyses highlighted phenylpropanoid and flavonoid biosynthesis, glutathione and nitrogen metabolism, ribosome biogenesis, and plant MAPK signaling. Metabolomic profiling identified changes in amino acid-, lipid-, secondary metabolite-, and antioxidant-related features. Integrated analysis and qRT-PCR validation further identified candidate genes associated with these responses. These findings characterize transcriptional and metabolic changes associated with the contrasting responses of the two oat germplasms to nitrogen deficiency and provide candidate genes, metabolites, and pathways for further investigation of low-nitrogen adaptation in oat.

Wheat grain quality is a complex traits governed by both genetic and environmental factors. Chinese winter wheat landraces on the Qinghai–Tibet Plate

Stripe rust (Puccinia striiformis f. sp. tritici) poses a major threat to Chinese wheat production. Assessing resistance levels and gene distribution in spring wheat landraces is critical for breeding durable resistant cultivars. This study evaluated 267 landraces from eight provinces for seedling resistance against dominant races CYR32/CYR34 and adult-plant resistance (APR) across five Qinghai natural disease nurseries during 2023-2024. At the seedling stage, 7.5 % (20 accessions; IT 0-6) and 12.4 % (33; IT 0-6) exhibited resistance to CYR32 and CYR34, respectively, with 2.99 % (8 accessions) conferring dual resistance. APR trials identified2.25 % (6 landraces) showed stable resistance, including Banjiemang with complete immunity (IT 0). Molecular analyses revealed prevalent Yr genes, Yr10 (38.6 %,103/267), Yr18 (29.6 %,79/267), Yr26 (20.9 %, 56/267) and multi-gene combinations 60 accessions (22.5 %) with 2 genes; 33 (12.4 %) with ≥3 genes. Notably, 97 accessions (36.3 %) lacked known Yr genes, suggesting novel resistance mechanisms. The Yr18/Yr26 combination emerged as a promising APR source. This study provides germplasm and genetic insights for pyramiding strategies to enhance stripe rust resistance.