Abstract Clubroot is an important root disease of canola/oilseed rape (Brassica napus L.) caused by Plasmodiophora brassicae. To cope with the emergence of new virulent pathotypes of P. brassicae that threaten canola production in western Canada, there is a need to identify novel sources of resistance for breeding programmes. In the present study, a series of nine B. napus genotypes, from different geographic origins, were screened for resistance to Canadian single-spore and field isolates of P. brassicae. The effect of nitrogen fertilization on the resistance level of these genotypes was also evaluated. Under full nitrogen fertilization, several of the tested host genotypes harboured isolate-specific partial resistance to P. brassicae infection, with some of these interactions resulting in disease indices <50. Accessions showing a partial resistance response to the novel pathotype 5X of P. brassicae also were identified. The influence of nitrogen on the level of resistance varied according to the specific plant genotype/pathogen isolate combination. Under low nitrogen fertilization, the genotype ‘Darmor-bzh’ showed a high level of partial resistance to isolates belonging to pathotypes 2 and 3, and ‘Express’ and ‘Grouse’ showed resistance to pathotype 2. The results confirm that nitrogen fertilization is an important factor to consider in combination with the use of resistant varieties for the management of clubroot.

中文翻译：

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冬季和春季欧洲油菜基因型的鉴定对加拿大白菜根瘤菌分离株具有部分抗性

摘要 根肿病是油菜(Brassica napus L.) 由Plasmodiophora brasicae 引起的一种重要的油菜(Brassica napus L.) 根病。为了应对威胁加拿大西部双低油菜籽生产的新的芸苔属病菌的出现，需要为育种计划确定新的抗性来源。在本研究中，对来自不同地理起源的一系列九种欧洲油菜基因型进行了筛选，以确定对加拿大单孢子和田间油菜分离株的抗性。还评估了施氮对这些基因型抗性水平的影响。在全氮施肥下，几个测试的宿主基因型具有分离株特异性的对芸苔属感染的部分抗性，其中一些相互作用导致疾病指数 <50。还鉴定了对芸苔属植物的新型致病型 5X 表现出部分抗性反应的种质。氮对抗性水平的影响根据特定植物基因型/病原体分离株的组合而变化。在低氮施肥下，基因型“Darmor-bzh”对属于致病型 2 和 3 的分离株表现出高水平的部分抗性，而“Express”和“Grouse”对致病型 2 表现出抗性。结合使用抗性品种管理根肿病要考虑的重要因素。