萝卜根肿病抗感品种间侵染过程及生理生化差异分析

根肿病是十字花科作物的重要病害之一，严重影响十字花科作物（油菜、白菜和萝卜等）的产量和品质。为探究根肿病的抗病机理，为防治十字花科根肿病进行田间早期的诊断预报提供依据，以两个抗病性不同的萝卜品种为试验材料，观察了根肿菌侵染的差异，利用qPCR技术测定了不同时间点根内根肿菌含量，并采用紫外分光光度法测定了其接种根肿菌后根部防御酶活性和可溶性糖含量。结果表明：根肿菌在两个萝卜品种中均发生根毛（初级）侵染，但是仅能在感病萝卜根中完成侵染循环，抗病萝卜没有观察到皮层（次级）侵染。推测次级游动孢子不能分化成休眠孢子囊是抗病萝卜抗病的主要原因。在接种后第25~45 d，感病萝卜根内的菌含量显著增加，抗病萝卜则相反，提示此期间是根肿菌在感病萝卜体内快速繁殖的重要时期。同时，接菌后抗病萝卜根部SOD活性、POD活性和可溶性糖含量高于感病品种，而CAT活性低于感病萝卜，表明较高的SOD、POD活性和可溶性糖含量以及较低的CAT活性对于萝卜的根肿病抗性具有重要的作用。

Infection process and physiological and biochemical differences between clubroot-resistant and -susceptible varieties of radish

Clubroot, one of the major diseases of crucifer crops, is caused by the obligate biotrophic protist Plasmodiophora brassicae. The disease seriously affects the yield and quality of crucifer crops (canola, cabbage, radish, etc.). To better understand the disease and for early diagnosis and prediction, 2 radish varieties were used in this study to explore the disease resistance mechanism of clubroot disease in host. The differences of infection process between resistant and susceptible radish were observed. qPCR was performed to detect the content of P. brassicae, and ultraviolet spectrophotometry were used to detect the activities of defensive enzymes and soluble sugar. Results showed that root hair (primary) infection occurred both in resistant and susceptible radish, while the cortical infection (secondary) only occurred in susceptible radish. It suggested that secondary zoospores fail to develop into resting sporangial plasmodium might be the reason of clubroot resistance in radish. During 25-45 d post inoculation (dpi), the pathogen content increased in the susceptible radish but decreased in the resistant radish significantly, suggesting that 25-45 dpi is an important period for rapid propagation in susceptible radish. Meanwhile, the activity of SOD, POD and soluble sugar content in the roots of resistant radish were higher than those of susceptible radish, but the activity of CAT in the roots of resistant radish was lower than the susceptible. It was indicated that the feature of higher of SOD, POD activity and soluble sugar content, and the lower CAT activity, might play a certain role for clubroot resistance in radish.