Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
Phytopathology. 2011 Dec;101(12):1424-32. doi: 10.1094/PHYTO-04-11-0124.
A study was conducted to assess the effect of temperature on infection and development of Plasmodiophora brassicae in the root cortex of Shanghai pak choy (Brassica rapa subsp. chinensis) and on subsequent clubroot severity. Ten-day-old seedlings were grown individually, inoculated with resting spores, and maintained in growth cabinets at 10, 15, 20, 25, and 30?C. Seedlings were harvested at 2-day intervals, starting 8 days after inoculation (DAI) and continuing until 42 DAI. Roots were assessed at 4-day intervals for the incidence of cortical infection and stage of infection (young plasmodia, mature plasmodia, and resting spores), at 2-day intervals for symptom development and clubroot severity, and at 8-day intervals for the number of spores per gram of gall. Temperature affected every stage of clubroot development. Cortical infection was highest and symptoms were observed earliest at 25?C, intermediate at 20 and 30?C, and lowest and latest at 15?C. No cortical infection or symptoms were observed at 42 DAI in plants grown at 10?C. A substantial delay in the development of the pathogen was observed at 15?C. Resting spores were first observed at 38 DAI in plants at 15?C, 26 DAI at 20 and 30?C, and 22 DAI at 25?C. The yield of resting spores from galls was higher in galls that developed at 20 to 30?C than those that developed at 15?C over 42 days of assessment. These results support the observation in companion studies that cool temperatures result in slower development of clubroot symptoms in brassica crops, and demonstrate that the temperature has a consistent pattern of effect throughout the life cycle of the pathogen.
一项研究旨在评估温度对上海白菜（芸薹亚种）根皮层中根肿菌的感染和发育以及随后的根肿病严重程度的影响。将 10 天大的幼苗分别种植，用休眠孢子接种，并在 10、15、20、25 和 30°C 的生长箱中维持。从接种后 8 天（DAI）开始，每隔 2 天收获一次幼苗，直到 42 DAI。每隔 4 天评估一次根皮层感染的发生率和感染阶段（幼原质团、成熟原质团和休眠孢子），每隔 2 天评估一次症状发展和根肿病严重程度，每隔 8 天评估一次每克瘿瘤中的孢子数。温度影响根肿病发展的各个阶段。在 25°C 时，皮层感染率最高，症状最早出现；在 20 和 30°C 时，感染率中等，症状出现居中；在 15°C 时，感染率最低，症状最晚出现。在 10°C 下生长的植物在 42 DAI 时未观察到皮层感染或症状。在 15°C 时观察到病原体的发育有明显延迟。在 15°C 时，首次观察到休眠孢子是在 38 DAI；在 20 和 30°C 时，在 26 DAI 观察到休眠孢子；在 25°C 时，在 22 DAI 观察到休眠孢子。在 42 天的评估中，在 20 至 30°C 下发育的瘿瘤中休眠孢子的产量高于在 15°C 下发育的瘿瘤。这些结果支持在配套研究中的观察结果，即低温导致十字花科作物根肿病症状的发展速度较慢，并表明温度在病原体整个生命周期中都具有一致的影响模式。
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