Pahonges Idetification Of Brown Rot Disease In Chinese Cabbage And Research Of Therapid Identification Method

Brown rot diease mainly infecting the petiole of Chinese cabbage could cause the rotting of petiole and affect the quality and quantity. It has been epidemic in recent years, and the experts did not pay enough attention to this disease, therefor, there are only a few reports about it nowadays.In this study, conventional identification, molecular identification and anastomosis group identification was used to identify the pathogens of brown rot disease in Chinese cabbage in Tianjin and Haerbin. We also analyzed its biological characteristics and the methods of resistance identification. The results are as follows:(1) The pathogens of brown rot disease in Chinese cabbage is Rhizoctonia solani through the conventional identification on the hyphae morphology, colony morphology and sclerotium morphology of the strains separated from brown rot disease in chinese cabbage in Tianjin (TJ)and Haerbin(DB)(2)Results of molecular identification indicated that the similarity between the sequence of5.8S rDNA-ITS of TJ and DB and the ITS sequences of Rhizoctonia solani isolate in GeneBank was100%and99%respectively. Phylogenetic t analyzation showed that TJ and DB strain were divided into the same category with other Rhizoctonia solani, and DB strains was a new strain of Rhizoctonia solani., the accenssion number of it in GenBank was JN412624.(3) Anastomosis group identification indicated that TJ strain is anastomosis with AG2and DB strain is anastomosis with AG1.(4) Comparison of biological characteristics between TJ strain and DB strain showed that:1. The same biological characteristics.①The optimal carbon sources of them was starch, and growth were the slowest when pectin was used as the main carbon sources; The optimal nitrogen source of them was the pepton, and growth were the slowest when glycine was used as the main nitrogen source; The most suitable temperature, PH and illumination were all25℃,7and12hours respectively.②Air sclerotias were inventively produced when the soluble starch was the carbon source, and they produced the biggest number of air sclerotia when the sugar was used as the carbon source;③The formation of air sclerotias was the fastest when ammonium sulfate was used as the main nitrogen source;④25℃was the optimal to the formation of air sclerotias and the half-buried sclerotias for two strains, and the best carbon sources for half-buried sclerotias is sugar.⑤The optimal pH for the formation of half-buried sclerotias and air sclerotias was pH7, and the littlest formation of them was pH5for two strains.⑥12hours was beneficial for the formation of air sclerotias and half-buried sclerotias, and24housr was not suitable for the formation of them. Besides, the lethal temperature for mycelial were all42℃.2. The differentias biological characteristics①The DB strains grown faster than TJ strains when the soluble starch and glucose were used as carbon source. The TJ strains grown faster than DB strain when fructose was used for carbon source.②Formation of half-buried sclerotias of TJ was faster and more than DB when potassium nitrate was used for nitrongen sources. Formation of half-buried sclerotias of DB was faster and more than TJ when ammonium nitrate was used for nitrongen sources.③The production of air sclerotias and half-buried sclerotias were the least for TJ at29℃, however, the least formation of half-buried sclerotias and air sclerotias for DB were21℃and29℃respectively.④The hypha of DB strain growned faster then TJ at the same condition.⑤The formation of sclerotias of TJ was faster and more than DB at the same condition.⑥Lethal temperature for sclerotium of TJ was46℃,and DB strain was48℃.(5) A set of rapid identification method was established for resistant on brown rot disease in Chinese cabbage. Through the research on pathopoiesia of different varieties showed that:the pathopoiesia rate of hyphae backing to the soil was bigger than the pathopoiesia rate of sclerotias, and the influence of thickness of hyphae was less to the pathopoiesia stage of seedling in Chinese cabbage; The optimal inoculated seedling stage was1-2leaf, and the optimal inoculated temperature was25℃at day and18℃at night; The optimal inoculated humidity was more than90%.