Abstract

Field surveys indicate blackleg of canola has increased in western Canada since 2010. Earlier studies showed changes in the pathogen (Leptosphaeria maculans (Sowerby) P.Karst.; Lm) population between 2007 and 2010–2011. In this study, Lm isolates were collected from trap plots (591) and/or commercial fields (372) on the prairies between 2012 and 2014, and tested for the profile of avirulence (Av) genes on a set of host differentials for 10 Lm Av alleles. Up to 35 ‘Westar’ trap plots were set up each year, and commercial fields were surveyed in the same area in 2012 and 2013. A similar trend was observed for Av profile between the two Lm populations; Av1, Av3, Av9 and AvLep2 were at low or very low levels, while Av2, Av4, Av6 and Av7 were present in >60% of the isolates. A total of 82 races were identified in these Lm populations, suggesting a greater diversity than those reported elsewhere. Margalef and Simpson indices also confirmed the greater genetic diversity in Lm. In fact, for each known R gene, there is at least one virulent race already existing in the Lm population. The races carrying Av2, Av4, Av6 or Av7 accounted for >70% of the Lm population, indicating that an R gene corresponding to any of these Av alleles may be effective against blackleg on the prairies. However, Av results alone appeared insufficient for explaining different levels of blackleg observed in canola fields; additional factors, possibly including crop rotation and local weather, may also play a role.

摘要

现场调查表明，油菜黑胫的在加拿大西部，因为在2010年的病原体的早期研究显示，改变已增加（十字花科小球腔（索尔）P.Karst; Lm的）2007年和2010 - 2011年间的人口。在这项研究中，Lm分离株是从 2012 年至 2014 年间大草原上的陷阱地块 (591) 和/或商业田地 (372) 中收集的，并在一组宿主差异中测试了 10 Lm的无毒 ( Av ) 基因 谱Av等位基因。每年设立多达 35 个“Westar”陷阱样地，并于 2012 年和 2013 年在同一地区调查了商业田。两个Lm种群之间的Av剖面观察到类似的趋势；Av1、Av3、Av9和AvLep2处于低水平或非常低水平，而Av2、Av4、Av6和Av7存在于 > 60% 的分离株中。在这些Lm种群中总共确定了 82 个种族，表明比其他地方报道的种族具有更大的多样性。Margalef 和 Simpson 指数也证实了Lm 中更大的遗传多样性。事实上，对于每个已知的R基因，Lm种群中至少已经存在一个有毒的种族。携带Av2、Av4、Av6或Av7 的种族占Lm种群的70% 以上，表明R与这些Av等位基因中的任何一个相对应的基因可能对草原上的黑腿病有效。然而，单独的Av结果似乎不足以解释在油菜田中观察到的不同程度的黑腿病；其他因素，可能包括轮作和当地天气，也可能起作用。