基于根肿菌早期侵染量的白菜抗性分析
Resistance analysis of Chinese cabbages to Plasmodiophora brassicae based on early infection in roots

为探究不同抗性白菜品种对根肿菌侵染量的影响,通过水培法观测4个白菜品种接种根肿菌后其在寄主根内的发展动态,实时荧光定量PCR检测技术对同期根内含菌量进行分析,并结合温室盆栽试验获得的各品种发病数据进行相关性分析。结果表明,早熟长江5号根肿病的发病率和病情指数分别为82.5%和36.2,华良早五号为66.7%和37.5,CR-春美为68.9%和36.0,可归为感病品种,而CR-英雄为52.5%和16.5,可归为抗病品种;水培法接种观测和PCR定量结果显示,根毛侵染率、皮层侵染数以及根内含菌量均表现为CR-英雄最低,显著低于其它3个品种。根毛侵染率、皮层侵染数、根内含菌量、发病率四者间呈显著相关,其R2最大值变幅为0.84~0.98,且根毛侵染率与根内含菌量、发病率与根内含菌量的最大相关系数均出现在第6天,说明根肿菌早期侵染量直接影响白菜根肿病的发生程度。表明根内早期侵染是根肿菌致病的关键环节,通过水培法观测并结合实时荧光定量PCR检测可以评价品种的抗性,可作为根肿病抗性评价的一种方法。
To analyze the effects of different resistant varieties of Chinese cabbages on the infection in roots by Plasmodiophora brassicae, the development dynamics in four varieties' roots were measured after inoculation under solution culture conditions. Furthermore, quantitative real-time PCR (qPCR) technology was adopted to detect P. brassicae DNA content in roots during the same period. Correlation analysis was finally conducted among the early infection indicators in roots. The results showed that the incidences/disease indexes of Zaoshuchangjiang 5, Hualiangzao 5, CR-Chunmei and CR-Yingxiong were 82.5%/36.2, 66.7%/37.5, 68.9%/36.0 and 52.5%/16.5, respectively. The former three varieties tested in the study were susceptible, while CR-Yingxiong was resistant. The root-hair infection rate, amounts of cortex infection, and P. brassicae DNA content in CR-Yingxiong were significantly lower than those of other three varieties. The correlation was also significant among root-hair infection rate, amounts of cortex infection, P. brassicae DNA content and disease incidence, and the maximum value of R2 ranged from 0.84 to 0.98. Additionally, the value of R2 reached the maximum at the 6th day after inoculation between P. brassicae DNA content and root-hair infection rate or disease incidence. It indicated that early infection level in roots directly affected the clubroot occurrence degree of Chinese cabbages varieties, suggesting that the early infection was a key process for P. brassicae pathogenicity. The study showed that the varieties' resistance can be evaluated by measurement of the early infection in roots, and detection of P. brassicae DNA content using qPCR method.