Biological Control And Mechanism Of Bacillus Subtilis BS193 Against Pepper Phytophthora Blight(Phytophthora Capsici)

Pepper phytophthora blight that caused by Phytophthora capsici is one of the notorious diseases in pepper cultivation.Generally,chemical pesticide was the main measures used to control pepper phytophthora blight,which can make pathogens drug-resistant and may induce problems as pesticide residues.Bio-control bacteria were widely used and have advantages in the future.In this study,a strain of Bacillus subtilis BS193 with bio-control activity was isolated from the early laboratory.And then,bio-control effects and antifungal mechanism of the strain BS193 were studied.Main results were as follows:(1)Broad-spectrum antifungal was found for Bacillus subtilis BS193 using plate cultivation method.Bacillus subtilis BS193 inhibited the growth of 10 plant pathogens from 9 genera which indicate biocidal potential and development prospects.(2)Bacillus subtilis BS193 had the good bio-control effects against pepper Phytophthora blight:Our results showed that the inhibitory effect of BS193 on the selection of four strains of P.capsici was stable.In vitro antifungal experiment,we found that BS193 inhibits infection of P.capsici blade and the efficiency reached 63.50%;In plot experiment,The results showed that the control effect of individuals,Sterile filtrate and fermentation broth were 30.75%,29.76%,52.56%,34.56%,and 23.53%.9 days after inoculation of the pathogen.In ninth day,the control efficacy of 1.0 ×108,1.0×106,1.0 X 105cfu · m L-1 BS193 fermentation broth were 52.56%,34.56%,23.53%.The seedlings watered roots with BS193 fermentation broth and inoculated the pathogen at 0,24,48 and 72 h,in ninth day the control efficacy were 23.43%,41.25%,49.41%and 51.44%,respectively.It can be seen that Bacillus subtilis BS193 has a good anti-disease effect against pepper Phytophthora blight.At the same time,it was found that BS193 fermentation broth also had the significant growth promoting effect on pepper seedling.Compared with the control group,the plant height,root length,fresh weight and dry weight of the capsicum were increased by 50.04%,48.16%,73.27%and 48.83%.(3)The aseptic filtrate of Bacillus subtilis BS193 has significant inhibitory activity against mycelial growth,sporozoite formation and zoospores germination of P.capsici:The results showed that the mycelial growth rate was decreased significantly after treatmented by sterile filtrate of BS193 strain.The morphological changes of mycelial were observed in optical and electron microscopy,including mycelial branching increased,deformity swelling,distortion,shrinkage.Phytophthora spores and zoospores germination were significantly reduced,while inhibition rate were significantly increased.(4)Using concentrated hydrochloric acid precipitation method and ULPC-QTOF/MS analysis,antifungal substances was primary identified from BS193.Moreover,significant antifungal activity was found.The three types of lipopeptides are Iturin,Feycin and Surfactin.