Study On Identification Of Clubroot Resistant Of Crucifers Cultivars, Biochemical Indexes And Screening Of Fungicides Controlling Clubroot, Caused By Plasmodiophora Brassicae

Crucifers clubroot, caused by Plasmodiophora brassicae, in Hunan has became more serious since1984, especially for Chinese cabbage and Brassica campestris L var. purpurea. Clubroot is one of the major soilborne diseases of crucifers and is widely distribution throughout the world. For present, the disease is difficultly controlling. Therefore, it is very important to explore and utilize new resistant varieties and resources, as well as to research other technologies in controlling clubroot. In this paper, the resistance of cruciferae crops planted in Hunan was identified, the related physiological and biochemical indexes were analyzed after inoculation with P. brassicae in cabbage, and fungicides against red brassica sproutsis clubroot were screened. The results were as follows:1. Resistance of106cruciferous cultivars (including1resistant and1susceptible variety as control check) to the clubroot was evaluated under the born-soil pathogen field, and artificial inoculation at seeding stage in greenhouse and tissue culture room. The results showed that there was obviously different among these cruciferous cultivars to clubroot resistance, in which10cultivars i.e. Baigengbaiye, Aijiaoxiaobaicai, Baimeigui, Zaobaicaitai IV, Youqingtiancaixin, Zaoshubaicaitai III, Degaofugui, Qiulv60, Zhongqiqingcai and Shantoutianbaicai were highly resistant, accounting for9.6%;7cultivars were resistant, accounting for6.7%;3cultivars were tolerant, accounting for2.9%;38cultivars were susceptible, accounting for36.5%; the other46cultivars displayed different resistant types or uncertainty in the above3identification methods.2. The contents of soluble sugar, CAT, POD, PAL and SOD of3cultivars with different resistant levels to clubroot after inoculation were detected. The results suggested that the changing rates of CAT, PAL and SOD contents of resistance cultivars(Baigengbaiye with highly resistant, Zaobaicaitai with tolerant resistant) after inoculation were higher than those of susceptible cultivar(Huangjinxiaobaicai); the POD activities of resistance cultivars reached a peak on a earlier day than those of susceptible cultivars; the increasing rate of soluble sugar of susceptible cultivars had two peaks which were higher than those of resistance cultivars.3. The performances of8fungicides against the clubroot of red brassica sproutsis (Brassica campestris L. var. purpurea) were tested by pot in greenhouse and field trial. The pot trial in greenhouse with two application,5days before seeding and at two-leaf plus central leaf stage, indicated that the efficacy of7fungicides except for fenaminosulf was all above70%at the trial dosages and the ordering of their efficacy from high to low was metalaxyl-mancozeb＞propineb> cyazofamid> chlorothalonil> fluazinam> pentachloronitrobenzene(PCNB)> fluopicolide-propamocarb. The trail in field with three application,5days before seeding transplanting and15days after transplanting, indicated that the efficacy of fluazinam, cyazofamid, chlorothalonil, metalaxyl-mancozeb and propineb was all above65%at seeding and adult stage, at above same trail dosages. Based on the efficacy and safety, cyazofamid and fluazinam can be used to control the clubroot of red brassica sproutsis, while there is phytotoxicity of fluazinam, metalaxyl-mancozeb and propineb for red brassica sproutsis, so the three fungicides can not be used to control the clubroot of B. campestris L. var. purpurea.