Screening Of Antagonistic Bacterium Against Ralstonia Solanacearum And Biocontrol Application Research

Tobacco bacteria wilt caused by Ralstonia solanacearum is the soil-born disease which is destructive to tobacoo, and widespread in tropical and subtropical tobacco growing areas, the disease is widespread occurrence and serious damage in South tobacco growing areas of China every year. In recent years, due to global climate change and farming patterns change, tobacco bacteria wilt often large area occurred in the South of Anhui, not only to farmers brought serious economic losses, but also greatly restricted the healthy and sustainable development of tobacco industry. Therefore, this study mainly carried out from soil of South Anhui tobacco area for bacteria screening,6 strains were screened, and the identification, fermentation and control effect were studied. The main points are as follows:1、Using the filter paper method selected XC1, XC2, XC3, XC4, XC5 and DZ1, 6 antagonistic strains of Ralstonia solanacearum have a strong inhibitory effect, which XC4 is stable, the diameter of inhibition zone is 12.5mm, so choose XC4 antagonistic bacteria as the main object of the follow-up tests. According to morphological observation, physiological and biochemical characteristics measured molecular identification and the United States Biolog microbial identification system determined XC4 is Streptomyces viridobrunneu.2、XC4 of antagonistic bacteria fermentation conditions were explored by single factor experiment to determine the optimum conditions. The results showed that the optimum fermentation conditions of the strain XC4 were fermenting 48h,30℃, pH 7.0, inoculum 2%, shaking at 190 r/min, beef extract as carbon source, and tryptone as nitrogen source. Under the optimized fermentation conditions, diameters of inhibition zone produced by the strain XC4 against Ralstonia solanacearum increased by 72% than before optimization from the original 12.5mm to 21.5m.3、Through affinity between 6 antagonistic bacteria were found,XC4 strain with antagonistic bacterial XC1, XC2, XC3 and DZ1 is part of the affinity, and XC5 completely incompatible, the XC4 strain suspension liquid respectively with the other 5 strains of antagonistic antiseptic mixed after testing the inhibitory effect of Ralstonia solanacearum, antagonistic bacteria XC4 results showed improved XC1, XC2, XC3 single bacterial wilt pathogen inhibition effect, but the difference was not significant, XC4+XC5 combination antibacterial the worst effect, only 3.3mm.4、By gradually increasing the concentration of rifampicin,6 strains of antagonistic bacteria of mutant strains XClRif, XC2Rif, XC3Rif,XC4Rif, XC5Rif and DZlRif as a late set determination of colonization ability of resistant strains were screened by resistance marker method. Different inoculation methods (mixed with soil, root pouring, spraying) and different inoculation time (seedbed period, transplanting period, the rosette period) XC4Rif antagonistic bacteria in the soil and roots influence colonization of tobacco, XC4Rif strain different inoculation methods colonization strength is:mixed with soil>root pouring> spraying, mixed with soil treatment XC4Rif strain colonization best, but in the field operation is not convenient, so root pouring approach more feasible; tobacco seedlings grow to the rosette period will XC4Rif strain root pouring treatment, in the soil and root colonization reached the peak value after 21 and 35 days, peak value is 6.92 lg·cfu/g and 2.40 lg-cfu/g, better than transplanting and treatment of seedbed. XC4Rif and other 5 mutant strains mixed inoculation in soil and tobacco root colonization systematically studied, the number of mixed colonization of antagonistic bacteria better than XC4Rif single bacteria, which XC4Rif+XC3Rif combination compared to other combinations best.5、Promoting effect was Studied on Yunyan 87 and Yunyan 97 of the antagonistic XC4. The results showed that the strain can promote the germination and on tobacco seedlings also has obvious role in promoting the growth. XC4 strain in greenhouse on tobacco bacterial wilt control effect for 54.40%, higher than 72% streptomycin (50.88%); also studied XC4 strain was mixed inoculated control effect, with other five trials showed antagonistic bacteria more coordination of control of tobacco bacterial wilt fungus validity and feasibility, mixed antagonistic bacteria combination XC4+XC2 and XC4+DZ1 complex better control effect of 57.90%and 58.71%, higher than XC4 single bacteria.