Abstract

Clubroot, caused by Plasmodiophora brassicae, is an important soilborne disease of canola (Brassica napus) in Alberta, Canada. As clubroot prefers acidic soils, the application of lime to increase soil pH may reduce disease. Replicated field plot experiments were conducted to evaluate the efficacy of hydrated lime for clubroot management. In 2017, moderate (11.4 t ha⁻¹) to high rates (12.7 t ha⁻¹) of hydrated lime reduced the index of disease (ID) by 35–91% in a susceptible canola cultivar 8 weeks after seeding. In contrast, no effect of lime treatment was observed in the 2018 field trials, due to several environmental factors. A greenhouse study compared the efficacy of hydrated lime and limestone in reducing ID in susceptible and resistant canola cultivars, at different application rates and inoculum concentrations. In treatments that did not receive lime, ID was very high (92–100%) in the susceptible and low (9–13%) in the resistant canola. The application of hydrated lime at 4.7, 8.1, 11.4 and 14.8 t ha⁻¹ eliminated visible symptoms in both cultivars, whereas limestone reduced the ID only at the two lowest inoculum concentrations. Root tissues from the same study were analyzed by quantitative PCR to measure P. brassicae proliferation in planta. Inoculum concentration and the type and rate of lime significantly affected the amount of P. brassicae DNA present in the root tissue. Repeated trials with less virulent inoculum indicated similar trends. Hydrated lime may represent a more effective tool than limestone to manage P. brassicae on canola in highly infested soils.

摘要

根肿病是由芸苔疟原虫引起的，是加拿大阿尔伯塔省油菜（欧洲油菜）的一种重要土传病害。由于根肿病喜欢酸性土壤，因此使用石灰来增加土壤 pH 值可能会减少疾病。进行了重复的田间试验，以评估熟石灰对根肿治疗的功效。2017 年，中等（11.4 t ha ^-1）到高比率（12.7 t ha ^-1) 的熟石灰在播种后 8 周使易感油菜品种的疾病指数 (ID) 降低了 35-91%。相比之下，由于多种环境因素，在 2018 年的现场试验中没有观察到石灰处理的效果。一项温室研究比较了熟石灰和石灰石在不同施用率和接种浓度下降低易感和抗性油菜品种 ID 的效果。在未接受石灰的处理中，易感油菜的 ID 非常高（92-100%），而抗性油菜的 ID 低（9-13%）。熟石灰的施用量为 4.7、8.1、11.4 和 14.8 t ha ^-1消除了两个品种的明显症状，而石灰石仅在两个最低接种浓度下降低了 ID。通过定量 PCR 分析来自同一研究的根组织，以测量植物中的芸苔属植物增殖。接种物浓度和石灰的类型和速率显着影响根组织中存在的P. brasicae DNA 的量。用毒性较小的接种物进行的重复试验表明了类似的趋势。熟石灰可能是比石灰石更有效的工具，可以在高度侵染的土壤中管理油菜上的芸苔属植物。