Identification Of Clubroot Resistant And Physiological Race Of Plasmodiophora Brassicae In Hunan Cruciferae Vegetable And QPCR Detection Of Soil-borne Pathogen

Clubroot, caused by Plasmodiophora brassicae Woron, is one of the worldwide diseases of cruciferous crops. The disease has been more severely occurred in cruciferae vegetable planting areas in Hunan and highly impact on the development of cruciferae vegetable production. Utilization of clubroot resistant varieties is a very important measure in integrated control clubroot. In this study, identification of the resistance of cruciferae vegetable varieties and physiological races of P.brassicae in Hunan, and detection of the soil borne-pathogen by real-time fluorescence quantitative PCR technology, as basis of integrated management clubroot, were conducted. Major results are as follows:1.178cruciferous varieties and1susceptible variety, Sijinaiyouxiaobaicai as control check, were evaluated by artificial inoculation in greenhouse and tissue culture room at seeding stage in Hunan. Results showed that54cultivars were resistant (disease index<20), accouting for31%in total178cruciferous varieties tested by the two methods. The above54cultivars were futher idntified under the born-soil pathogen field in Taojiang and Xupu, in which47cultivars showed resistance to clubroot. The ratio of the resistant cultivars in the greenhouse, tissue culture room and clubroot nursery in total tested cultvars reached26.4%, among which5varieties Huaganyihao, YR Chunleiganlan, Ziganerhao, Ganxin70and XiabaoganlanFl, displayed immune to clubroot in3kinds of identification methods. Therefore the5varieties have very important application value in the clubroot occurrrence areas.2. The races of P. brassicae from27clubroot plants of cruciferae crops, Chinese cabbage and red brassica sproutsis in four different disease areas, Changsha, Xiangtan, Yiyang and Huaihua in Hunan were identified by the Williams system in2013. The results showed that five races,1,5,8,9and11were identified, among which they were22.3%,18.5%,14.8%,33.3%and11.1%in total races, respectively. Based on the cruciferae crops, there were1,5,9and11race in Chinese cabbage, while races in red brassica sproutsis hold8,9and11; according to areas distribution of races, races of Chinese cabbage in Changsha, Xiangtan, Huaihua, Yiyang hold5and9,1,9,1and11respectively, races of red brassica sproutsis in Xiangtan and Yiyang hold8and11,8and9respectively. Race9was the main physiological race among27clubroot samples in Hunan.3.94soil samples collected from clubroot areas, Changsha, Huaihua and Yiyang were detected by fluorescence quantitative PCR. The results displayed that104to106resting spores/g soil spores of P. brassicae of all soil samples except for the negative control and no incidence soil with qPCR detection could cause the clubroot occurrence of cruciferous crops. When susceptible variety Sijinaiyouxiaobaicai was inoculated with the gradient concentrations of P. Brassicae resting spores from109to100spores/g soil, the result indicated that109-103spores/g soil could cause clubroot, while the disease index increased with spores concentrations. Therefore103spores/g of soil is the lowest concentration of clubroot disease. Using specific primers DC1F/DC1R and plasmid gradient dilution method to establish a fluorescence quantitative standard curve in the experiment,1.24X102spores/g in artificial inoculation soil was detected by qPCR. So, the qPCR detection system is sensitive and accurate, which it can quantitatively detect number of resting spores in field soil.