Triticeae Research Institute, Sichuan Agricultural University, Chengdu, Sichuan 611130, China; and Department of Plant Pathology, Washington State University, Pullman 99164-6430.
Department of Plant Pathology, Washington State University.
Plant Dis. 2017 Aug;101(8):1522-1532. doi: 10.1094/PDIS-12-16-1786-RE. Epub 2017 May 25.
Stripe (yellow) rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease of wheat in the world. The obligate biotrophic fungal pathogen changes its virulence rapidly, which can circumvent resistance in wheat cultivars and cause severe epidemics. Because P. striiformis f. sp. tritici races have been identified in the United States using different wheat genotypes in different time periods, it is difficult to make direct comparisons of the current population with historical populations. The objective of this study was to characterize historical populations with 18 Yr single-gene lines that are currently used to differentiate P. striiformis f. sp. tritici races in order to understand virulence and race changes of the pathogen over 40 years in the United States. From 908 P. striiformis f. sp. tritici isolates collected from 1968 to 2009 in the United States, 171 races were identified and their frequencies were determined. More races, more new races, and races with more virulence genes were detected since the year 2000 than prior to 2000. None of the races were virulent to Yr5 and Yr15, indicating that these genes have been effective since the late 1960s. Virulence genes to the remaining 16 Yr genes were detected in different periods, and most of them increased in frequency over time. Some virulence genes such as those to Yr17, Yr27, Yr32, Yr43, Yr44, YrTr1, and YrExp2 appeared 14 to 37 years earlier than previously reported, indicating the greater value of using Yr single-gene lines as differentials. Positive and negative associations were detected between virulence genes. The continual information on virulence and races in the P. striiformis f. sp. tritici populations is useful for understanding the evolution of the pathogen and for breeding wheat cultivars with effective resistance to stripe rust.
条锈病（黄锈病），由条形柄锈菌小麦专化型引起，是世界范围内小麦的一种严重病害。这种专性活体营养真菌病原体的毒性迅速变化，这可以规避小麦品种的抗性，并导致严重的流行。由于在美国不同时期使用不同的小麦基因型来鉴定条形柄锈菌小麦专化型的小种，因此很难将当前种群与历史种群进行直接比较。本研究的目的是利用目前用于区分条形柄锈菌小麦专化型小种的 18 个单基因系来描述历史种群，以了解 40 多年来美国病原体的毒性和小种变化。从 1968 年至 2009 年在美国采集的 908 个条形柄锈菌小麦专化型分离物中，鉴定出 171 个小种，并确定了它们的频率。自 2000 年以来，检测到更多的小种、更多的新小种和具有更多毒性基因的小种，而 2000 年之前则较少。没有一个小种对 Yr5 和 Yr15 有毒性，表明这些基因自 20 世纪 60 年代末以来一直有效。在不同时期检测到对其余 16 个 Yr 基因的毒性基因，并且随着时间的推移，它们中的大多数的频率增加。一些毒性基因，如 Yr17、Yr27、Yr32、Yr43、Yr44、YrTr1 和 YrExp2 ，比之前报道的出现时间早 14 到 37 年，这表明使用 Yr 单基因系作为鉴别寄主具有更大的价值。在毒性基因之间检测到了正相关和负相关。条形柄锈菌小麦专化型种群中关于毒性和小种的持续信息有助于了解病原体的进化，并培育出对条锈病具有有效抗性的小麦品种。
