Uloth Margaret, You Ming Pei, Finnegan Patrick M, Banga Surinder S, Yi Huang, Barbetti Martin J
School of Plant Biology, Faculty of Science, The University of Western Australia, Crawley, WA, 6009, Australia.
Department of Plant Breeding and Genetics, Punjab Agricultural University, Ludhiana, 141004 Punjab, India.
Plant Dis. 2014 Feb;98(2):184-190. doi: 10.1094/PDIS-06-13-0612-RE.
Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a serious disease of many cruciferous crops and frequently poses a threat to the sustainable and profitable production of these crops worldwide. Differences in seedling resistance to S. sclerotiorum across 46 diverse cruciferous genotypes from 12 different species were assessed by comparing the extent of pathogenesis on inoculated cotyledons under controlled conditions. Selections of Brassica carinata, B. incana, B. juncea, B. napus, and B. napus introgressed with B. carinata, B. nigra, B. oleracea, B. rapa var. rosularis, B. rapa var. chinensis, B. tournefortii, Raphanus raphanistrum, R. sativus, and Sinapis arvensis were tested. The average size of lesions on cotyledons 48 h post inoculation varied from 0.8 to 7.3 mm. The three most resistant genotypes with the smallest lesions were all from B. oleracea (viz., B. oleracea var. italica 'Prophet' and B. oleracea var. capitata 'Burton' and 'Beverly Hills'). Representatives of R. raphanistrum, S. arvensis, B. juncea, and B. carinata were the most susceptible to S. sclerotiorum, with the largest lesions. To our knowledge, this is the first report of high levels of resistance to S. sclerotiorum in B. oleracea at the cotyledon stage and also the first report of the host cotyledon reactions against S. sclerotiorum for all tested species except B. napus and B. juncea. The mean lesion size for B. napus introgressed with B. carinata was 5.6 mm, which is midway between the lesion size for the two parent species B. napus (5.1 mm) and B. carinata (5.8 mm). Separate genetic control for cotyledon versus mature plant resistance was demonstrated by the lack of correlation between lesion size from S. sclerotiorum on the cotyledon with the severity of disease initiated by stem inoculation or natural processes in a previous field test. On the most resistant genotypes, B. oleracea var. italica Prophet and var. capitata Burton, growth of S. sclerotiorum on the cotyledon surface prior to penetration was severely impeded, production of appressoria inhibited, and both cytoplasm shrinkage and protoplast extrusion in S. sclerotiorum hyphae prevalent. This is the first report of such resistant mechanisms in B. oleracea. Genotypes with cotyledon resistance identified in this study will be of great value not only in furthering our understanding of resistance mechanisms across different cruciferous species but also could be exploited for developing commercial crucifer cultivars with high-level resistance against S. sclerotiorum.
由核盘菌引起的菌核病是许多十字花科作物的一种严重病害，经常对全球这些作物的可持续盈利生产构成威胁。通过比较在受控条件下接种子叶上的发病程度，评估了来自12个不同物种的46种不同十字花科基因型对核盘菌的幼苗抗性差异。测试了埃塞俄比亚芥、灰白芥、芥菜、甘蓝型油菜以及导入了埃塞俄比亚芥、黑芥、甘蓝、油菜变种rosularis、油菜变种小白菜、硬毛芥、野萝卜、萝卜和田野毛茛的甘蓝型油菜。接种后48小时子叶上病斑的平均大小在0.8至7.3毫米之间。病斑最小的三种抗性最强的基因型均来自甘蓝（即意大利芥‘Prophet’、结球甘蓝‘Burton’和‘Beverly Hills’）。野萝卜、田野毛茛、芥菜和埃塞俄比亚芥的代表对核盘菌最敏感，病斑最大。据我们所知，这是首次报道甘蓝在子叶阶段对核盘菌具有高水平抗性，也是除甘蓝型油菜和芥菜外所有测试物种对核盘菌的寄主子叶反应的首次报道。导入埃塞俄比亚芥的甘蓝型油菜的平均病斑大小为5.6毫米，介于两个亲本物种甘蓝型油菜（5.1毫米）和埃塞俄比亚芥（5.8毫米）的病斑大小之间。在前一个田间试验中，子叶上核盘菌病斑大小与茎接种或自然过程引发的病害严重程度之间缺乏相关性，这证明了子叶抗性与成熟植株抗性的遗传控制是分开的。在最抗病的基因型意大利芥‘Prophet’和结球甘蓝‘Burton’上，核盘菌在穿透前在子叶表面的生长受到严重阻碍，附着胞的产生受到抑制，核盘菌菌丝中普遍出现细胞质收缩和原生质体挤出现象。这是甘蓝中此类抗性机制的首次报道。本研究中鉴定出的具有子叶抗性的基因型不仅在进一步了解不同十字花科物种的抗性机制方面具有重要价值，而且可用于培育对核盘菌具有高抗性的商业十字花科品种。
