Blackleg, which is caused by the ascomycete fungus Leptosphaeria maculans, is a major disease of canola in Canada and worldwide. In Canada, canola is usually grown in rotation once every three to four years to limit yield losses. Recently, growers in Canada have begun to grow canola more intensively due to growing market demand driven by crop profitability and improved cultivars. A 4-year study at the Ian N. Morrison Research Station, Carman Manitoba, was conducted from 2014 to 2017 to investigate the effectiveness of five introgression lines (IL) carrying single blackleg resistance genes under field conditions in a 2-year canola–wheat rotation. Blackleg incidence for all tested R genes, except Rlm4, was reduced by a maximum of 16% in 2017 compared to 2014. Disease severity was 31–44% higher in the first year for all tested R genes, except for the Rlm2 when canola was seeded on the same stubble, compared to the fourth year rotation. Relative disease severity, calculated based on the susceptible check Westar, showed that the R genes LepR1, LepR3, Rlm2, and Rlm4 were resistant (<30% of check) against L. maculans after 4 years of rotation, whereas Rlm3 resistance was less effective (35% of check). The results of our 2-year rotation study suggest that canola cultivars harbouring the major resistance genes LepR1, LepR3, Rlm2, and Rlm4 will remain effective against blackleg when grown in the increasingly common 2-year rotation, rather than the recommended 3–4 year rotation. As expected, the regression analysis confirmed that seed yield declined as blackleg severity increased. However, comparatively some ILs were more impacted in terms of yield loss as disease severity increased, and can be ordered from the most to the least resistant as follows: Rlm2 ≈ LepR1 > Rlm3 ≈ Rlm4 > LepR3.

黑腿病是由子囊菌真菌Leptosphaeria maculans引起的，是加拿大和世界范围内油菜的主要疾病。在加拿大，油菜通常每三到四年轮种一次，以限制产量损失。最近，由于作物盈利能力和改良品种推动的市场需求不断增长，加拿大的种植者开始更加密集地种植油菜。2014 年至 2017 年在卡曼马尼托巴省 Ian N. Morrison 研究站进行了一项为期 4 年的研究，以调查 2 年油菜小麦在田间条件下携带单个黑腿抗性基因的五个渐渗系 (IL) 的有效性回转。所有测试的R基因的黑腿发生率，除了Rlm4，与 2014 年相比，2017 年最多减少了 16%。对于所有测试的R基因，第一年的疾病严重程度高出 31-44% ，除了Rlm2，当油菜籽播种在同一根茬上时，与第四年相比年轮换。基于易感检查 Westar 计算的相对疾病严重程度表明，R基因LepR1、LepR3、Rlm2和Rlm4在轮换 4 年后对L. maculans具有抗性（<30% 的检查） ，而Rlm3抵抗力较差（检查的 35%）。我们为期 2 年的轮作研究结果表明，含有主要抗性基因LepR1、LepR3、Rlm2和Rlm4的油菜品种在越来越普遍的 2 年轮作中（而不是建议的 3-4 年轮作）仍能有效对抗黑腿病。回转。正如预期的那样，回归分析证实种子产量随着黑腿严重程度的增加而下降。然而，相对而言，随着疾病严重程度的增加，一些 ILs 在产量损失方面受到的影响更大，并且可以从最高到最低抗性排序如下：Rlm2 ≈ LepR1 > Rlm3 ≈ Rlm4 > LepR3。