Screening, Colonization And Application Of Bio-control Bacteria Against Tobacco Bacterial Wilt

Tobacco bacteria wilt caused by Ralstonia solanacearum is the soil-born disease which is destructive to tobacco. There are no effective and environmentally harmonious methods to control it as yet. In the study, some bacterial strains were studied to control the disease.Screening of biocontrol bacteria showed the stains FT12, F08, Y05 had strongly colonizing capacity and antagonistic action to R. solanacearum. And bio-control agent against bacterial wilt in greenhouse indicated that the average control effects of three strains were 70.21%(FT12),70.70%(F08) and 60.69%(Y05), respectively. Meanwhile strains FT12, F08, Y05 had a wide spectrum of inhibiting plant pathogen. According to morphological, physiological and biochemical characteries, strains FT12, F08 and Y05 were preliminarily identified and FT12 belongs to Bacillus subtilis,F08 and Y05belong to Bacillus laterosporus.Colonization ability of three biocontrol agents Bacillus subtilis B001, B. brevis B011 and B. laterosporus 2-Q-9 were determined by the method of dual-resistant marker. The result showed that three biocontrol bacteria had a strong colonizing ability and the best was B011 in strain's single inoculations. The antagonistic test showed that mutual antagonism between three bio-control strains had no occurrence but the antibacterial activities against R. soanacearum were improved. And colonizing abilities of two strains'associative inoculations in tobacco were generally increased but B011 and 2-Q-9 in mixture inoculation of three strains were inhibited. Furthermore, the total populations of mixed strains reached the maximum values on 60th d after dipping tobacco roots treatment.In order to further stabilize and improve the control effects of three biocontrol agents B001, B011 and 2-Q-9 on tobacco bacterial wilt, the control effects of B001, B011 and 2-Q-9 were tested by the combined inoculation ways of root-soaking, root-watering, stem-injecting, fermented rapeseed-cake and chemical way of streptomycin-spraying. The field trial indicated that effects of different combined treatments on tobacco bacterial wilt were all better than that of single 72% agricultural streptomycin treatment. Impacts of the biocontrol bacteria mixed with fermented rapeseed-cake on tobacco bacteria wilt were better than that of the non-mixed, so did combined injection treatments vs. the corresponding non-injection; and combined treatments of 2-Q-9 plus agricultural streptomycin were superior to the single 2-Q-9 treatment, but the joint treatments of streptomycin plus B001 or BO 11 inhibited the two strains'antibacterial activities against R. soanacearum. Furthermore, The control effects of B001 and B011,which were treated by combined ways of fermented rapeseed-cake, root-watering and stem-injecting, reached 51.37%(B001), 71.20%(B011), respectively, and efficiencies of fermented rapeseed-cake, root-watering of 2-Q-9 plus streptomycin-spraying were 62.32%The combination test of bio-control strains B001, B011 and 2-Q-9 indicated that effects of single bio-strain and mixtures on tobacco bacterial wilt were all better than that of 4000X of 72% agricultural streptomycin, and the mixed treatments of the two strains were also superior to corresponding single bacterium's. Particularly, efficiencies of B011+2-Q-9 and B004+B011 against the disease reached 83.39% and 78.34%, respectively, but effect of B001+B011+2-Q-9 was only 45.49%.