Isolation And Mechanism Of Biocontrol Strain AC29 Against Phytophthora Sojae

Phytophthora sojae is one of the most important plant pathogens, and could cause plant disease. This disease always causes multibillion-dollar crop losses in agricultural production. Currently, the use of chemical pesticides to prevent the Phytophthora pathogens could cause serious resistance and pesticide residues problems. Biological control shows great potential of development, which could effectively control the diseases without causing environment pollution.The strain AC29 was isolated from Changshu, and showed good antagonistic effect to Phytophthora sojae. The inhibition rate was above 50.0% at the 6th day. Strain AC29 shows good antagonistic effect on leaves and bean sprouts in vitro. The inhibit efficiency of the mycelial growth and spore suspension of Phytophthora sojae by AC29 were 57.5% and 23.0% respectively. AC29 also has good efficiency in greenhouse. By morphological, physiological and biochemical characterises, and analysis of 16S rDNA sequence, strain AC29 was identified as Bacillus sp..The supernatant of strain AC29 showed no antagonistic effect to P. sojae, which implied that the antagonism of strain AC29 was impossible by antibiotics or bacteriocins. The inhibition rate was above 50.0% when P.sojae exists, which might be induced by certain signaling molecules. Studies found that strain AC29 could secretion cellulase, siderophore, and protease, which could affect mycelial growth and sporangium germination of P.sojae. Strain AC29 which was marked of GFP could form biofilm and had high efficiency of colonization ability in vitro. Antagonistic mechanism of strain AC29 might be associated with cellulase, siderophore and protease.Exploring the growth conditions of strain AC29 showed the best growth temperature, pH and aeration are 30℃,7.5 and 160 rpm respectively. Sucrose and yeast extract are the optimal carbon and nitrogen. AC29 growth curve was obtained under optimum growth conditions. By the growth curve, strain AC29 entered into the logarithmic growth phase in 6 h, stationary phase in 14 h.