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Abstract：
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a crucial disease for wheat worldwide and constantly threatens wheat production in southwestern and northwestern China, where the environment is a good fit for Pst oversummering and overwintering. However, the underlying genetic dynamics of spring epidemic Pst populations across large areas of continuous planting in the southwestern and northwestern regions are poorly understood. A total of 2,103 Pst isolates were sampled in the spring of 2019 from the two agroecosystems and grouped into three horizontal spatial scales (countywide, provincial, and regional subpopulations) and two vertical spatial scales that consisted of elevational and geomorphic subpopulations. A total of 776 multilocus genotypes were identified, with the highest genetic diversity found in the northern and Sichuan populations, particularly in the Ningxia and Sichuan Basins, while the lowest genetic diversity was found in the Yunnan and Guizhou populations. Multivariate discriminant analysis of principal components (DAPC) and STRUCTURE (STRUCTURE 2.3.4) analyses revealed variation in the genotypic compositions of the molecular groups on horizontal and vertical dimensions from north to south or vice versa and from low to high or vice versa, respectively. The regional neighbor-joining tree revealed three large spatial structures consisting of the southwestern, the northwestern, and the Xinjiang regions, while the Tibetan population connected the southwestern and northwestern regions. The isolates of the Sichuan Basin were scattered over the four quartiles by principal coordinate analysis, which indicated frequent genotype interchange with others. Greater genetic differentiation was observed between the southwestern and northwestern regions. Linkage equilibrium (P ≥ 0.05) was detected on different spatial scales, suggesting that Pst populations are using sexual reproduction or mixed reproduction (sexual and clonal reproduction) in southwestern and northwestern China. IMPORTANCE Understanding the epidemiology and population genetics of plant pathogens is crucial to formulate efficient predictions of disease outbreaks and achieve sustainable integrated disease management, especially for pathogens with migratory capability. Here, this study covers the genetic homogeneity and heterogeneity of different geographical Pst populations on broad to fine spatial scales from the key epidemic regions of the two agroecosystems in China, where wheat stripe rust occurs annually. We provide knowledge of the population genetics of Pst and reveal that, for instance, there is greater genetic diversity in northwestern China, there are close genetic relationships between Yunnan and Guizhou and between Gansu-Ningxia and Qinghai, and there are effects of altitude on genetic compositions, etc. All of these findings clarify the genetic relationships and expand the insights into the population dynamics and evolutionary mechanisms of Pst in southwestern and northwestern China, providing a theoretical basis for achieving sustainable control of wheat stripe rust in key epidemic regions.
摘要：
小麦条锈病,由条锈病引起。小麦（Pst），是世界范围内小麦的重要疾病，并不断威胁着中国西南和西北地区的小麦生产，那里的环境非常适合Pst夏季和越冬。然而,对西南和西北地区大面积连续种植的春季流行Pst种群的潜在遗传动态知之甚少。2019年春季，从两个农业生态系统中总共采样了2,103个Pst分离株，并分为三个水平空间尺度（全县范围，省,和区域亚群）和两个垂直空间尺度，由海拔和地貌亚群组成。共鉴定出776个多位点基因型,在北部和四川人群中发现了最高的遗传多样性，特别是在宁夏和四川盆地，而云南和贵州种群的遗传多样性最低。主成分的多元判别分析（DAPC）和结构（结构2.3.4）分析揭示了分子组的基因型组成在水平和垂直维度上的变化，从北到南，反之亦然，从低到高，反之亦然。分别。区域邻居连接树揭示了三个大的空间结构，包括西南部，西北部，和新疆地区，而藏族人口连接着西南地区和西北地区。通过主坐标分析，四川盆地的分离物分散在四个四分位数上，这表明与其他人频繁的基因型互换。在西南地区和西北地区之间观察到更大的遗传分化。在不同的空间尺度上检测到连锁平衡(P≥0.05)，这表明Pst种群在中国西南部和西北部正在使用有性生殖或混合生殖（有性生殖和克隆繁殖）。重要性了解植物病原体的流行病学和群体遗传学对于制定疾病暴发的有效预测和实现可持续的综合疾病管理至关重要。特别是对于具有迁移能力的病原体。这里,本研究涵盖了中国两个农业生态系统主要流行区不同地理Pst种群的遗传同质性和异质性，每年都会发生小麦条锈病。我们提供了Pst种群遗传学的知识，例如,中国西北部有更大的遗传多样性，云南和贵州之间以及甘肃-宁夏和青海之间有密切的亲缘关系，海拔高度对遗传组成有影响，等。所有这些发现澄清了中国西南和西北地区Pst的遗传关系，并扩展了对Pst种群动态和进化机制的认识，为实现重点疫区小麦条锈病的可持续防治提供理论依据。
