Investigation On Plasmodiophora Brassicae In Chengdu And Hungicides Screening In Field

Cabbage clubroot in Chengdu was discovered in 1989. In recent years, cabbage clubroot in surrounding areas of Chengdu were very serious and spread speedily, it had been one of main plant diseases to cruciferae vegetables in Chengdu. Presently, cabbage clubroot spread in all vegetable depots in Sichuan province, and seriously threaten the sustainable development of vegetable industry. The study researched the distribution of cabbage clubroot in surrounding areas of Chengdu, degree of compromise to cultivar and screening of prophylactic agents for providing effectively cruciferae vegetable clubroot to happen, the results were as follows:1 Distribution of cabbage clubroot in surrounding areas of Chengdu was identified through surveying compromise of clubroot in 15 towns which around Chengdu. The results showed that cabbage clubroot had spread in most of cruciferae vegetable depots in surrounding areas of Chengdu, specifically in Wenjiang areas and Xindu county cabbage clubroot spread speedily, while in Shuangliu county and Pi county relatively slowly. Variability of compromise of cabbage clubroot to different cultivar was excellent, compromise to chinese cabbage and pakchoi was serious, while compromise to brassica oleracea and radish was slight.2 Screening prophylactic agents, and had choosen19 kinds of antifungal drugs and one kind of biological agent. Inhibition ratio of spores germination was determined respectively in the sixth day and the tenth day, the result showed that Cyazafamid,Bacillus,Thiodiazole-copper,Chlorothalonil,Fluazinam had strong and resistant inhibiting capacity to pores germination of cabbage clubroot germ.3 Indoor inhibiting capacity of 12 kinds of fungicides and one kind of biologic agent was determined by pores germination rate method on the basic of drug screening, and analyzed the results. The results showed that the EC50 of Cyazafamid,Bacillus and Thiodiazole-copper was low, while the inhibiting effect was the most excellent. The precedence ordering of inhibiting capacity of 13 kinds of drugs to pores germination was Bacillus> Cyazafamid> Thiodiazole-copper> Polyoxin> Fluazinam> chlorothalonil> Mancozeb-fosetyl-aluminium> Zine> Thiophanate-Methyl> Dimethomorph> Carbendazim> Propineb> Metalaxyl-Mancozeb.4 Experiments on 9 kinds of medicamentous potted plants indicated that the average pathogenetic index of Cyazafamid and Thiodiazole-copper treated was 26.71% and 29.36% respectively, the average index of prevented effect was 65.82% and 62.03% respectively, it demonstrated the prevented effect of the two kinds of treatments were excellent. While the average pathogenetic index of Mancozeb & Fosetyl-aluminium,Thiophanate-Methyl,Zine and Polyoxin was high, and the prevented effect was obsolete.5 50% Fluazinam SC and 10% Cyazafamid SC which were screened through spraying and root irrigating had excellent prevented effect to cabbage clubroot according to the results of potency experiment, while the prevented effects of other drugs were obsolete.All above research achievements provided significant scientific guidance to reasonable geography, regional treatment and prevention of disease of cruciferae vegetable cultivars in surrounding areas of Chengdu.