Isakeit T, Woodward J E, Niu C, Wright R J
Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843.
Department of Plant and Soil Science, Texas Tech University, Lubbock 79403.
Plant Dis. 2010 Jun;94(6):792. doi: 10.1094/PDIS-94-6-0792B.
During the past several years, canola (Brassica napus L.) has been grown experimentally in different areas of Texas to evaluate its potential as a crop, particularly for use as a biofuel source. In early April 2007, symptoms typical of Sclerotinia stem rot were observed in a canola variety trial that was flowering in Wharton County, Texas. Stems had white mycelia growing on the outside, or a bleached appearance, near the soil surface and plants were lodging. Inside bleached stems, there were spherical to cylindrical, black sclerotia that were 3 to 10 mm. Isolations from surface-disinfested stems onto potato dextrose agar (PDA) consistently yielded white, fluffy colonies with sclerotia typical of Sclerotinia sclerotiorum (Lib.) de Bary (1). Sequence analyses were conducted on two replicates of mycelium by extracting fungal DNA with the Qiagen DNeasy Plant Mini Kit (Valencia, CA). PCR amplification was performed using two primer sequences (92-4 AF377919: TCGCCTCAGAAGAATGTGC/AGCGGGTTACAAGGAGATGG; and 119-4 AF377925: GTAACAAGAGACCAAAATTCGG/TGAACGAGCTGTCATTCCC) (2) that have previously been used to characterize S. sclerotiorum (3). The BLAST search revealed that the sequences were 99 and 98% homologous with S. sclerotiorum Accession Nos. AF377919 and AF377925 over 376 and 377 bp of aligned sequence, respectively. Agar segments (1 cm) from a 5-day-old culture grown on PDA were placed in the leaf axils of 15 2-month-old canola plants ('Wichita') growing in pots. Plants were placed in a humid chamber under fluorescent lights at 16 to 22°C. After 2 days, water soaking and necrosis occurred on petioles and stems adjacent to the inoculum, but not on plants treated with sterile PDA. S. sclerotiorum was consistently reisolated from symptomatic tissue plated on acidified PDA. The inoculations were repeated once with similar results. To our knowledge, this is the first report of Sclerotinia stem rot of canola in Texas. Currently, there is no significant canola production in Texas; however, interest in biofuels could lead to an increase in planted acres. Sclerotinia stem rot of canola could become a significant disease problem in areas of Texas where canola is planted as a winter crop. References: (1) L. M. Kohn. Phytopathology 69:881, 1979. (2) C. Sirjusingh and L. M. Kohn. Mol. Ecol. Notes 1:267, 2001. (3) J. E. Woodward et al. Plant Dis. 92:1468, 2008.
在过去几年里，油菜（甘蓝型油菜）已在得克萨斯州的不同地区进行试种，以评估其作为一种作物的潜力，特别是作为生物燃料来源的潜力。2007年4月初，在得克萨斯州沃顿县一个正在开花的油菜品种试验田中，观察到了油菜菌核病的典型症状。茎干靠近土壤表面处长有白色菌丝体，或呈现漂白状外观，植株出现倒伏。在漂白的茎干内部，有3至10毫米的球形至圆柱形黑色菌核。从表面消毒的茎干上分离到马铃薯葡萄糖琼脂（PDA）培养基上，持续长出白色、蓬松的菌落，并带有油菜菌核病菌（核盘菌）（Lib.）de Bary典型的菌核（1）。使用Qiagen DNeasy植物微量提取试剂盒（加利福尼亚州瓦伦西亚）从两份菌丝体重复样本中提取真菌DNA，进行序列分析。使用两个先前用于鉴定核盘菌的引物序列（92 - 4 AF377919: TCGCCTCAGAAGAATGTGC/AGCGGGTTACAAGGAGATGG；和119 - 4 AF377925: GTAACAAGAGACCAAAATTCGG/TGAACGAGCTGTCATTCCC）（2）进行PCR扩增（3）。BLAST搜索显示，在分别比对376和377 bp的序列上，这些序列与核盘菌登录号AF377919和AF377925的同源性分别为99%和98%。将在PDA培养基上培养5天的菌块（1厘米）放置在15株盆栽2月龄油菜植株（“威奇托”品种）的叶腋处。植株置于湿度箱中，在16至22°C的荧光灯下培养。2天后，接种物附近的叶柄和茎干出现水渍状和坏死现象，而用无菌PDA处理的植株则未出现。从接种到酸化PDA培养基上出现症状的组织中持续重新分离到核盘菌。接种重复一次，结果相似。据我们所知，这是得克萨斯州油菜菌核病的首次报道。目前，得克萨斯州没有大量的油菜种植；然而，对生物燃料的兴趣可能导致种植面积增加。在得克萨斯州将油菜作为冬季作物种植的地区，油菜菌核病可能会成为一个严重的病害问题。参考文献：（1）L. M. Kohn. 植物病理学69:881, 1979. （2）C. Sirjusingh和L. M. Kohn. 分子生态学笔记1:267, 2001. （3）J. E. Woodward等人. 植物病害92:1468, 2008.
