Study On Biocontrol Of Bacterial Leaf Streak With Antagonistic Bacillus

Bacillus amyloliquefaciens are rich in species and widely distributed on soil and the surfaces of plants.Bacillus amyloliquefaciens is becoming a microbial pesticide development potential of microbial species with the discovery of Bacillus amyloliquefaciens has the ability to inhibit a variety of plant pathogens in recent years.9763 Bacillus strains were isolated from paddy soil collected from various areas in Guangxi and Hunan.310 Bacillus strains with antagonistic ability to Bacterial Leaf Streak,were obtained using Oxford Cup method and the size of inhibition zone diameter as screening indicator.After repeated screening,theJF48 strain,which the diameter of inhibition zone to Xanthomonas oryzae pv.oryzicola reached 37±3 mm,was selected as the further study strain with stable antagonistic ability.By the morphology,physiological,biochemical and 16S rDNA sequence analysis,it was identified that the strain belong to Bacillus amyloliquefaciens strain.By shake flask culture,explored the effect of different carbon source,nitrogen source,inorganic,liquid volume,rotation,initial pH,culture temperature and inoculation on spore production and sporulation rate in Bacillus amyloliquefaciens JF48 fermentation.On the basis of single factor experiment,Plackett Burman test showed that corn flour,soybean meal and temperature were significant influencing factors of spore yield.After optimization of the response surface,the optimal spore culture conditions of Bacillus amyloliquefaciens JF48 were as follows:Corn flour 14.69 g/L,soybean meal 9.54 g/L,CaCl2 2 g/L,NaCl 5 g/L,MgS04 1 g/L,liquid volume 50 mL/250 mL,rotation 200 rpm,initial pH 7.5,temperature 38?,inoculation 1%.Under this fermentation condition,the spore production of JF48 strain reached 3.6×109 cfu/mL,which was 105 times that of optimizing before.By single factor tests,the optimal formulation of the wetting powder of Bacillus amyloliquefaciens JF48 strain were confirmed as follows:the content of carrier diatomite 10%,surfactant PEG 10%,stabilizer K2HP04 2%,UV protection agents VC 0.1%.The result showed that the wettable powder of Bacillus amyloliquefaciens JF48strain spores content was 5.6×109 cfu/g,the suspension rate was 76%,the wetting time was 56s.In the pot experiment,the incidence of rice in the experimental group was lower than that in the blank group.This indicates that the strain of Bacillus amyloliquefaciens JF48 strain has significant antagonistic ability to Xanthomonas oryzae pv.oryzicola in rice plants.