Jin Y, Szabo L J, Rouse M N, Fetch T, Pretorius Z A, Wanyera R, Njau P
United States Department of Agriculture-Agricultural Research Service, Cereal Disease Laboratory, University of Minnesota, St. Paul 55108.
Department of Plant Pathology, University of Minnesota, St. Paul 55108.
Plant Dis. 2009 Apr;93(4):367-370. doi: 10.1094/PDIS-93-4-0367.
The stem rust resistance gene Sr36 confers a near-immune resistance reaction to many races of Puccinia graminis f. sp. tritici and is highly effective against race TTKSK (syn. Ug99), which possesses unusually broad virulence combinations. Because this gene is widely used in United States soft winter wheat germplasm and cultivars, it has been considered to be an important source of resistance to TTKSK. In 2007, moderately susceptible infection responses were observed on wheat lines and cultivars carrying Sr36 in a field screening nursery for stem rust at Njoro, Kenya. We derived 18 single-pustule isolates from stem rust samples collected from the 2007 Njoro nursery. The isolates were evaluated for virulence on 20 North American stem rust differential lines and on wheat lines and cultivars carrying Sr36, Sr31+Sr36, and Sr24+Sr31. Of the 18 isolates, 10 produced infection types 3+ to 4 on line W2691SrTt-1 (monogenic for Sr36) and other lines that carry Sr36 and belonged to a new virulence phenotype that was not detected in previous years. These isolates were identified as race TTTSK. The remaining eight isolates were identified as races TTKSK (five isolates) and TTKST (three isolates), with avirulence and virulence, respectively, to Sr24. Thirteen simple sequence repeat (SSR) markers were used to examine the genetic relationships among the three races in the TTKS lineage. All isolates in the lineage shared an identical SSR genotype and were clearly different from North American races. In all, 16 wheat cultivars and 60 elite breeding lines, postulated to possess Sr36, were susceptible to race TTTSK. The occurrence of race TTTSK with combined virulence on Sr31 and Sr36 has further broadened the virulence spectrum of the TTKS lineage and rendered an important source of resistance ineffective.
抗秆锈病基因Sr36对许多小麦秆锈菌（Puccinia graminis f. sp. tritici）生理小种表现出近乎免疫的抗性反应，并且对具有异常广泛毒力组合的TTKSK生理小种（同义词Ug99）具有高效抗性。由于该基因在美国软质冬小麦种质和品种中广泛使用，它被认为是对TTKSK抗性的重要来源。2007年，在肯尼亚Njoro的一个秆锈病田间筛选苗圃中，观察到携带Sr36的小麦品系和品种出现中度感病的侵染反应。我们从2007年Njoro苗圃采集的秆锈病样本中获得了18个单疱锈菌分离株。这些分离株在20个北美秆锈病鉴别品系以及携带Sr36、Sr31+Sr36和Sr24+Sr31的小麦品系和品种上进行了毒力评估。在这18个分离株中，有10个在品系W2691SrTt-1（单基因携带Sr36）和其他携带Sr36的品系上产生了3+至4级的侵染类型，属于一种往年未检测到的新毒力表型。这些分离株被鉴定为TTTSK生理小种。其余8个分离株被鉴定为TTKSK生理小种（5个分离株）和TTKST生理小种（3个分离株），分别对Sr24无毒力和有毒力。使用13个简单序列重复（SSR）标记来研究TTKS谱系中这三个生理小种之间的遗传关系。该谱系中的所有分离株共享相同的SSR基因型，并且与北美生理小种明显不同。总共16个小麦品种和60个假定携带Sr36的优良育种系对TTTSK生理小种敏感。具有对Sr31和Sr36联合毒力的TTTSK生理小种的出现进一步拓宽了TTKS谱系的毒力谱，并使一个重要的抗性来源失效。
