Pretorius Z A, Szabo L J, Boshoff W H P, Herselman L, Visser B
Department of Plant Sciences, University of the Free State, Bloemfontein 9300, South Africa.
USDA-ARS, Cereal Disease Laboratory, University of Minnesota, St. Paul 55108.
Plant Dis. 2012 Apr;96(4):590. doi: 10.1094/PDIS-12-11-1027-PDN.
Seven races have been described in the Ug99 race group of Puccinia graminis f. sp. tritici (2). Ug99-related races previously recorded in South Africa are TTKSF, TTKSP, and PTKST (4). In December 2010, severe stem rust infection of the winter wheat cv. Matlabas was observed for the first time in South Africa. Race analysis using the 20 North American (NA) stem rust differential lines and letter code system classified the race as TTKSF. In comparative infection studies in a greenhouse, cv. Matlabas seedlings were susceptible (infection type [IT] 4) to isolate UVPgt61/1 (TTKSF+) collected from Afrikaskop in the eastern Free State, whereas the cultivar was resistant (IT 1 to 2) to stem rust isolates 2013 (TTKSF), UVPgt55 (TTKSF), UVPgt59 (TTKSP), and UVPgt60 (PTKST). Isolate 2013 represents the original collection of race TTKSF in South Africa (1). In addition to the NA differentials, no variation in the IT range of seedlings of lines with Sr7a, 8b, 12, 13, 14, 16, 18, 19, 22, 25, 26, 27, 28, 29, 32, 33, 34, 35, 39, 41, 42, 43, 44, Em, R, Tt2, and Satu was observed between UVPgt61/1 and UVPgt55. With the exception of cv. Matlabas, ITs of 106 South African cultivars likewise did not differentiate UVPgt61/1 and UVPgt55. Seedling IT studies were conducted at least twice. Microsatellite analysis (4) showed that all single pustule isolates established from the original Matlabas isolate formed part of the Ug99 group. When characterized with selected single nucleotide polymorphisms (SNPs), all single pustule isolates shared an identical genotype that differed from UVPgt55 (TTKSF), a foreign introduction into South Africa (1,3). SNP genotype analysis suggests that UVPgt61/1 is genetically dissimilar to UVPgt55, as is Zim1009, another TTKSF+ isolate that was collected from Birchenough in Zimbabwe. Studies are underway to determine the identity of the defeated Sr gene in Matlabas and the cultivar has been added to the South African stem rust differential set. TTKSF+ is the eighth race detected in the Ug99 group. Since no other cultivars or advanced lines were found to carry the Matlabas gene, it is unlikely that race TTKSF+ will threaten wheat production in South Africa. However, the occurrence of a new Ug99-related race emphasizes the variability within this internationally important group. References: (1) W. H. P. Boshoff et al. Plant Dis. 86:922, 2002. (2) R. F. Park et al. Euphytica 179:109, 2011. (3) B. Visser et al. Mol. Plant Pathol. 10:213, 2009. (4) B. Visser et al. Euphytica 179:119, 2011.
已在小麦条锈菌Ug99种族组中描述了七个小种（2）。先前在南非记录的与Ug99相关的小种为TTKSF、TTKSP和PTKST（4）。2010年12月，在南非首次观察到冬小麦品种Matlabas发生严重的秆锈病感染。使用20个北美（NA）秆锈病鉴别系和字母编码系统进行的小种分析将该小种分类为TTKSF。在温室的比较感染研究中，品种Matlabas的幼苗对从东自由邦的阿非利卡斯科普采集的分离株UVPgt61/1（TTKSF+）敏感（感染类型[IT]为4），而该品种对秆锈病分离株2013（TTKSF）、UVPgt55（TTKSF）、UVPgt59（TTKSP）和UVPgt60（PTKST）具有抗性（IT为1至2）。分离株2013代表了南非TTKSF小种的原始采集（1）。除了NA鉴别系外，在Sr7a、8b、12、13、14、16、18、19、22、25、26、27、28、29、32、33、34、35、39、41、42、43、44、Em、R、Tt2和Satu品系的幼苗IT范围内，未观察到UVPgt61/1和UVPgt55之间存在差异。除了Matlabas品种外，106个南非品种的IT也未区分UVPgt61/1和UVPgt55。幼苗IT研究至少进行了两次。微卫星分析（4）表明，从原始Matlabas分离株建立的所有单疱分离株均属于Ug99组。当用选定的单核苷酸多态性（SNP）进行表征时，所有单疱分离株共享相同的基因型，该基因型与UVPgt55（TTKSF）不同，UVPgt55是引入南非的外来品种（1,3）。SNP基因型分析表明，UVPgt61/1在遗传上与UVPgt55不同，从津巴布韦的伯奇努夫采集的另一个TTKSF+分离株Zim1009也是如此。正在进行研究以确定Matlabas中被击败的Sr基因的身份，并且该品种已被添加到南非秆锈病鉴别系中。TTKSF+是在Ug99组中检测到的第八个小种。由于未发现其他品种或高级品系携带Matlabas基因，因此TTKSF+小种不太可能威胁南非的小麦生产。然而，一种新的与Ug99相关的小种的出现强调了这个国际重要群体内部的变异性。参考文献：（1）W. H. P. Boshoff等人，《植物病害》86:922，2002年。（2）R. F. Park等人，《欧洲植物病理学报》179:109，2011年。（3）B. Visser等人，《分子植物病理学》10:213，2009年。（4）B. Visser等人，《欧洲植物病理学报》179:119，2011年。
