Screening, Identification And Performance Of Endophytic Biocontrol Strains Against Solanaceae Bacterial Wilt Caused By Ralstonia Solanacarum

Bacterial wilt of solanaceae plants, caused by Ralstonia solanacearum, is a devastating soil-borne bacterial disease. In order to screening value antagonistic endophytic bacteria strains against R. solanacarum, antagonistic endophytic bacteria strains with inhibiting effect on pepper R. solanacearum were isolated from stems of different healthy solanaceae plants in bacterial wilt areas. In this paper, the antagonistic activity and performance against R. solanacarum, main biological characteristics, culture optimization and effect of greenhouse control on tomato bacterial wilt were systematically studied. The main results are as follows:(1) Screening and identification of endophytic antagonistic bacteria strains351endophytic bacteria strains with dilution plate and streak purification method were isolated from healthy plants of tomato, eggplant and pepper in bacterial wilt areas in Changsha, Hunan.28strains with antagonistic effect on R. solanacearum among351strians were screened by agar diffusion method, which the strains with antagonistic effect accounted for8.0%in total strains. The strain L009and L010had the best antagonistic performance against R. solanacarum with their radius of inhibition zone separately reached7.0mm and6.5mm after cultivation for24h. Based on the morphology and culture characteristics, and physiological and biochemical tests, and16S rDNA analysis, L009was identified as Bacillus amyloliquefaciens, the accession number is JF698724, while L010was identified as Serratia marcescens, holding its accession number JF698725.(2) The biological characteristics of the two strainsThe optimum growth temperature and pH of L009was25℃～35℃and7.0～7.5, respectively. L009strain could utilize sucrose, maltose, glucose, D-mannitol, α-lactose, D-xylose, D-fructose and corn starch for carbon sources except for D-arabinose. Furthermore, tryptone, peptone, beef extract, yeast extract, soybean powder and potassium nitrate could be used as nitrogen sources by L009, but casein and ammonium chloride could not be utilized.The optimum growth temperature and pH of L010was25℃～33℃and7.5～8.0respectively. The carbon and nitrogen utilization capacity of L010was a little different from L009. Strain L010could grow with sucrose, maltose, glucose, D-mannitol, D-arabinose, D-xylose and corn starch, D-fructose and α-lactose could not be utilized. Also it could grow with five kinds of organic nitrogen, but inorganic nitrogen included potassium nitrate, casein and ammonium chloride could not be utilized.(3) Optimization of fermentation conditions of L009The single factor experiment and orthogonal experiments showed that the optimum culture medium were corn starch8%, soybean powder6%, NaCl0.5%, CaCO30.5%and K2HPO40.08%, pH7.0and culture conditions original acted as fermentation time60h, temperature28℃, shake rotation160r/min and liquid volume100mL. The statistical analyses of the experimental results were completed by DPS data analysis software.(4) The greenhouse experimentsGreenhouse experiments of endogenous strains controlling tomato bacterial wilt was preliminary studies in2013. The results showed that L009had efficacy of63.4%on tomato bacterial wilt, which was better than agricultural streptomycin.These results provided kinds of practical basis for riching the biological control resource against solanaceae plants wilt, and also provided technical basis for the industrial production of biocontrol agents.