Study On The Biocontrol Bacteria D3-1 Against Potato Virus Y On Tobacco

Tobacco is an important agricultural cash crop.Potato Virus Y(PVY)is becoming serious in tobacco-growing areas of Hunan Province,which limits the yield and quality of tobacco.In this study,the antagonistic strains were separated from the tobacco field soil to further identify the taxonomic status by morphological identification,physiological and biochemical characteristics and molecular biological characteristics.The mechanism of the antagonistic strain D3-1 was preliminary study by whole genome sequencing analysis of the active metabolites.The results are as follows:1.124 bacterial strains were successfully isolated and identified.5 strains showed obviously resistance to PVY,which were obtained by the blight spot method.Interestingly,the inhibition rate of the antagonistic strain D3-1 to PVY reached 99.71%.2.The antagonistic strain D3-1 was identified as Bacillus evelzensis by morphological identification,physiological and biochemical characteristics,16 S r DNA sequence alignment.3.The fermentation conditions of the antagonistic strain D3-1 were optimized.The results showed that the optimum fermentation conditions for strain D3-1 to PVY were LB medium,Ph 7.0,1.5%,30 °C and 180 r / min,72 h,respectively.4.The results showed the inhibition rate of the fermentation broth of antagonistic strain D3-1 to PVY decrease after 60℃ treatment.In the range of PH5-9,the inhibition rate of antagonistic strain D3-1 remained above 90%.After 8 hours of ultraviolet irradiation,the inhibition rate of antagonistic strain D3-1 could still reach 96%.5.Field trials were conducted to verify the biological control effect of D3-1.The incidence rate and disease index of artificial inoculation of PVY and control area were77.48% and 32.74,respectively.The incidence rate and disease index of D3-1 fermentation broth treatment area were 46.09% and 14.04,respectively.The relative control effect of D3-1fermentation broth reached 57.12%.6.The expression level of PR1 genes was obviously up-regulated in the tobacco plants treated with D3-1 fermentation broth.7.The D3-1 chromosome genome contains 12 secondary metabolite synthesis gene clusters by genomic sequencing analysis,including of three antibacterial substances(Bcillibactin,Fengycin and macrolactin).There is a lipopeptide active product Surfactin in D3-1,which may invulve in anti-virus.