Screening, Identification And Antifungal Activity Of Antagonistic Rhizospheric Bacillus SP. LW-6against Tobacco Bacterial Wilt

Tobacco bacteria wilt caused by Ralstonia solanacearum is the soil-borndisease which is destructive to tobacco. There are no effective andenvironmentally harmonious methods to control it as yet.In the study，somebaeterial strains were studied to control the disease. Therefore, looking for thenon-pollution measures to prevent and control the plant diseases, screening anddeveloping new microbial fungicides for tobacco bacteria wilt is veryimportant. This research aimed at isolating and screening the microbes withstrong antagonism against tobacco bacteria wilt from the soil samples of healthytobacco rhizosphere in high incidence tobacco fields, and investigation on itstaxonomic status, antifungal activity and mechanism to get a new microbialpesticide resources against Ralstonia solanacearum.From the30soil samples of healthy tobacco rhizosphere in high incidencetobacco fields in Longyan, Sichuan Johnson, Hanzhong, Shaanxi and otherplaces, etc.,780strains of bacteria were isolated by plant dilute. selecteddirectionally with Ralatonia solanacearum.The resultss showed that3bacteriumhad strong activity, and strains LW-6had better activity, and the inhibition zonediameters against Ralstonia solanacearum were21.05mm.The antagonistic bacteria LW-6was identified based on morphological,physiological and biochemical characteristics, and16S rDNA phylogeneticanalysis. The resultss showed that the morphological characteristics,physiological and biochemical characteristics of LW-6was consistent with thepattern bacterial of Bacillus, which could resist acid, alkali, salt, and hightemperature, and its sequence is similar to Bacillus methylotrophicus in theNCBI, of which similarity is100%. Based on the above characteristics, thestrain LW-6was identified as B. methylotrophicus.The methods of Bonsai experiment in greenhouse were used to determineLW-6inhibition and plant growth-promoting. The results showed after treated with LW-6,the control effect on tobacco reached70.37%. LW-6can colonizeon tobacco rhizosphere soil had a good ability of colonization. the strain hasobvious promoting effect on the seedling growth. which had potential value inbiological control against tobacco bacterial wilt.