Ali S, Francl L J, De Wolf E D
Department of Plant Pathology, North Dakota State University, Fargo 58105.
Plant Dis. 1999 Jun;83(6):591. doi: 10.1094/PDIS.1999.83.6.591A.
Tan spot, caused by Pyrenophora tritici-repentis, is an important foliar disease of wheat worldwide. The fungus produces two distinct symptoms, necrosis (nec) and chlorosis (chl), on susceptible wheat genotypes. Fungal isolates have been grouped into five races based on their ability to induce necrosis and/or chlorosis on differentials Glenlea, Katepwa, 6B365, and Salamouni (1). Moreover, the isolates were designated on their ability to induce necrosis and chlorosis as follows: nec+chl+ (necrosis and chlorosis), nec+chl- (necrosis only), nec-chl+ (chlorosis only), and nec-chl- (neither symptom). Races 3 and 5 induce extensive chlorosis (nec-chl+) on 6B365 and Katepwa, respectively. Race 5 was reported on durum from North Africa. Races 1 to 4 were described from North America (1,2). During 1998, a survey of durum fields was conducted in the primary durum-growing area of North Dakota to assess the virulence pattern of P. tritici-repentis. Fifty-two single-spore isolates were obtained from diseased leaves. The isolates were evaluated for their virulence by inoculating them individually onto 15 seedlings of each wheat differential in the greenhouse. Forty-nine of 52 isolates were grouped as race 1 (nec+chl+) and three isolates, obtained from the Langdon Experiment Research Station, were grouped as race 5 (nec-chl+). Race 5 isolates were evaluated three times and consistently induced extensive chlorosis on Katepwa. This is the first report of the occurrence of race 5 outside of North Africa. This race may threaten wheat in the United States, so cultivars and germplasm should be evaluated for resistance. More isolates are under investigation to obtain a comprehensive virulence pattern of the pathogen population in the United States. References: L. Lamari and C. C. Bernier. Can. J. Plant Pathol. 11:49, 1989; (2) L. Lamari et al. Can. J. Plant Pathol. 17:312, 1995.
由小麦黄斑病菌（Pyrenophora tritici-repentis）引起的小麦黄斑病是一种在全球范围内对小麦叶部危害严重的病害。该真菌在感病的小麦基因型上会产生两种不同的症状，即坏死（nec）和褪绿（chl）。根据真菌分离株在鉴别品种Glenlea、Katepwa、6B365和Salamouni上诱导坏死和/或褪绿的能力，已将其分为五个生理小种（1）。此外，根据分离株诱导坏死和褪绿的能力，将其命名如下：nec+chl+（坏死和褪绿）、nec+chl-（仅坏死）、nec-chl+（仅褪绿）和nec-chl-（无任何症状）。生理小种3和5分别在6B365和Katepwa上诱导大面积褪绿（nec-chl+）。在北非的硬粒小麦上报道过生理小种5。生理小种1至4是在北美描述的（1,2）。1998年，在北达科他州主要的硬粒小麦种植区对硬粒小麦田进行了调查，以评估小麦黄斑病菌的毒力模式。从病叶上获得了52个单孢分离株。通过在温室中将每个分离株单独接种到15株每个小麦鉴别品种的幼苗上，对这些分离株的毒力进行了评估。52个分离株中有49个被归类为生理小种1（nec+chl+），从兰登实验研究站获得的3个分离株被归类为生理小种5（nec-chl+）。对生理小种5的分离株进行了三次评估，其在Katepwa上始终诱导大面积褪绿。这是生理小种5在北非以外地区发生的首次报道。这个生理小种可能会对美国的小麦构成威胁，因此应对品种和种质进行抗性评估。正在对更多的分离株进行研究，以全面了解美国病原菌群体的毒力模式。参考文献：L. Lamari和C. C. Bernier。《加拿大植物病理学杂志》11:49，1989；（2）L. Lamari等人。《加拿大植物病理学杂志》17:312，1995。
