United States Department of Agriculture- Agricultural Research Service Cereal Disease Laboratory, St.Paul, MN, USA.
Phytopathology. 2010 Apr;100(4):376-83. doi: 10.1094/PHYTO-100-4-0376.
Leaf rust, caused by Puccinia triticina, is the most prevalent and widespread disease of wheat in South America. The objective of this study was to determine whether genetically differentiated groups of P. triticina are currently present in South America and to compare the South American population with the previously characterized population in North America. In total, 130 isolates of P. triticina from the wheat-growing regions of Argentina, Brazil, Chile, Peru, and Uruguay, mostly from the 1990s to 2008, were tested for virulence on 20 lines of wheat with single genes for leaf rust resistance and for molecular genotypes with 23 simple-sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotypes, 99 isolates were included for further analysis. Principal coordinate analysis plots indicated five different groups of isolates based on SSR genotypes that also differed for virulence to leaf rust resistance genes. All pairs of groups, except for one pair, were significantly differentiated for SSR genotypes according to R(ST) statistics. All but two pairs of groups were significantly differentiated for virulence phenotype according to Phi(PT) statistics. Isolates in all five groups had high values of fixation index for SSR alleles and linkage disequilibrium was high across all isolates that indicated the clonal reproduction of urediniospores. Only one of the five P. triticina groups from South America was differentiated for SSR genotypes from all of the six P. triticina groups from North America. The high degree of similarity for SSR genotype of isolates from both South America and North America suggested a common European origin of P. triticina that was introduced to both continents. The emergence of the same P. triticina virulence phenotypes with highly related SSR genotypes in the United States in 1996 and in Uruguay in 1999 indicated the likely intercontinental migration of these genotypes from Mexico to both South America and North America.
叶锈病，由小麦叶锈菌引起，是南美洲小麦最普遍和广泛的病害。本研究的目的是确定目前在南美洲是否存在遗传分化的小麦叶锈菌群体，并将南美种群与之前在北美的特征种群进行比较。共检测了来自阿根廷、巴西、智利、秘鲁和乌拉圭小麦种植区的 130 个小麦叶锈菌分离株，这些分离株主要来自 20 世纪 90 年代至 2008 年，用含有 20 个小麦叶锈病抗性单基因的品系和 23 个简单重复序列（SSR）标记的分子基因型对其进行了毒性测定。在去除具有相同毒性和 SSR 基因型的分离株后，有 99 个分离株被纳入进一步分析。主坐标分析图表明，基于 SSR 基因型，有 5 个不同的分离株群体，这些群体在对叶锈病抗性基因的毒性方面也存在差异。除了一对群体外，所有群体对 SSR 基因型的差异均达到显著水平，根据 R(ST)统计数据。根据 Phi(PT)统计数据，除了两对群体外，所有群体在毒性表型上均有显著差异。所有五个群体的 SSR 等位基因固定指数均较高，所有分离株的连锁不平衡程度均较高，表明了夏孢子的无性繁殖。来自南美的 5 个小麦叶锈菌群体中，只有一个群体的 SSR 基因型与来自北美的 6 个小麦叶锈菌群体的基因型不同。来自南美的和北美的分离株的 SSR 基因型非常相似，这表明小麦叶锈菌可能具有共同的欧洲起源，然后被引入这两个大陆。1996 年在美国和 1999 年在乌拉圭出现的相同小麦叶锈菌毒性表型与高度相关的 SSR 基因型表明，这些基因型可能从墨西哥向南北美洲进行了洲际迁移。
