Study Of Resistance Identification For Clubroot And The Related Analysis Of Physiological And Biochemical Mechanism In Different Brassica Crops

Clubroot, caused by the soil-borne obligate biotroph Plasmodiophora brassicae Woronin,is one of the most serious diseases in the world.Any cruciferous of the susceptible varieties can be infected by the pathogen,and it greatly decreases the yields and quality of cruciferous crop under appropriate conditions In recent years, the brassica clubroot expands quickly in our country, causing serious losses of cruciferous vegetables.At present, the best way to prevent and control clubroot is to breed disease-resistant varieties.Useful and simple inoculation method is the basis of disease resistance breeding.As we all know,the artificial inoculation is easily affected by environmental conditions and so on.But when the artificial inoculation combined with the molecular marker assisted selection,it will be more accurate.However, it brings serious challenges to disease resistace breeding because of the pathogenicity differentiation phenomenon of Plasmodiophora brassicae.So,it makes grest sence to undertake the studies of pathogenic races is indispensable,and the result of identification is directly related to effective breeding disease-resistant varieties.At the same time,physiological and biochemical mechanism of cruciferous crops root disease resistance is also more complicated,the determination of the changement of relevant the physiological and biochemical indexes can be used as auxiliary method of resistant identification.From these perspectives, this study on root pathogens identified from the nationalwide;inoculation of Plasmodiophora brassicae in seeding stage in room and marker-assisted selection are used to identify clubroot-resistance of 94 cultivars of different Brassica crops.At the same time,we analyed the changement of related physiological and biochemical indexes before and after inoculation,in order to root disease resistance breeding and provide theoretical basis for pathogenesis.The main results were as follows:1. The use of Williams identification system for 10 Plasmodiophora brassicae from different places of the country’s for indoor artificial inoculation.The results showed that,the pathogentic races in wulong chongqing, wuhan hubei, nyingchi Tibet, chengdu, shifang sichuan, linhai zhejiang and other places is No. 4;the pathogentic races in chongqing fuling is No.15;the pathogentic races in yunnan province is No.1.That is to say,the pathogentic type in our country is the main of No.4,at the same time there are other small kind of differentiation.2. On the basis of physiological small kind of appraisal,94 cultivars of different Brassica crops were analyzed the resistance to clubroot which was caused by Plasmodiophora brassicae Woron., and the cauliflower variety ‘jingyan 60’ was used as control to conduct resistant inoculation experiment via artificial in greenhouse.The results showed that there were 24 high resistant varieties,63 resistant varieties and 7 tolerant resistant.The method of using marker-assisted selection was conducted to the 24 high resistant varieties,results showed that all of them have CRa gene.That is to say,the material is resistant to the pathogentic races of No.4 in theory.3.Study of related physiological and biochemical index of cabbage cilbroot.(1)The soluble sugar content:All varieties of cabbage contained lower content of soluble sugar after inoculation,but without any rules.(2)The soluble protein content: The tolerant varieties of cabbage contained higher content of soluble protein after inoculation,but the resistant varieties of cabbage reduced after inoculation.So, the soluble protein content can be used as auxiliary means of the resistance identification for cabbage to clubroot after inoculation.(3)The MDA content: All varieties of cabbage contained higher content of MDA after inoculation,but this change without any rules.(4)The antioxidant enzyme activities: For different resistance of cabbage,after inoculation,the SOD 、 PPO activity was increased and the resistance varieties of cabbage increased more fast than the tolerant varieties of cabbage.After inoculation, the POD activity also was increased,but there is no obvious between the resistant and the tolerant varieties of cabbage. In addition, the change of CAT activity was unordered and haphazared sfter inpculation.To sum up,the SOD and PPO activity can be used as auxiliary means for the resistance identification to clubroot after inoculation.