Studies On Biocontrol Of Pepper Phytophthora Blight

As a biocontrol microorganism,bacteria B4 and actinomycetes A10 against Phytophthora capsici were isolated and screened from pepper rhizosphere.B4 and A10 are systematically researched on following aspects:isolating and screening,identification, optimum fermentation condition,colonization,controling effect,growth promotion,activity of defensive enzyme in pepper and so on.Results as follow:1.Isolation and screening of Biocontrol Bacteria and Actinomycetes against Pepper Phytophthora BlightTaking diluteing soil screening method,298 stains of bacteria and 265 stains of actinomycetes strains were isolated from pepper rhizosphere in Liaoning province.Activities of bacteria B4 and actinomycetes A10 were measured by method of inhibition zone and growth rate of hyphae.The results showed that strains and the sterilized ferment filtrate had a significantly inhibition on hyphae growth and the sporangia germination of Phytophthora capsici.The results also showed that hyphae were distortion,fracture,inflate,malformation and more ranification.The cell walls had breaked.Protoplasm had overflowed.The bacteriolysis phenomenon had occurrence.It could reduce the rate of the sporangia germination.At the same time,they could promote the pepper seeds to sprout.2.Identification of Bacteria B4 and Actinomycetes A10Classification strains of B4 and A10 were defined by morphology,cultural character physiological and biochemical properties.Results suggested that B4 was Bacillus pumilus and A10 was theWhite Second Cluster of Streptosporangium.The characteristic of A10 was similar to S.durhamensis,but the detailed classification status of it needed to do the Member Identification.3.Studies on Fermentation Condition of Bacteria B4 and Actinomycetes A10By single favtor and orthogonal test,Screening the optimal fermentation medium and the best optimal fermentation conditions of biocontrol Bacteria B4 and Actinomycetes A10.The results were as follows:the liquid medium of fermentation of B4 constituted by soybean flour1%,glucose0.5%,sodium chloride 0.3%,potassoium nitrate 0.5%.The fermentation conditions included the optimum temperature 30℃,optimum initial pH7.0～7.5,inoculation seed liquid 4%and loading liquid 50ml in 250 flasks.The liquid medium of fermentation of A10 constituted by soybean flour1%,soluble starch 1.5%,tryptone 0.5%,sodium chloride 0.3%,calcium carbonate 0.25%。The fermentation conditions included the optimum temperature 26℃,optimum initial Ph5.5, culture time 96h,inoculation seed liquid 6%and loading liquid 80 ml in 250 flasks.4.Dynamic Influence of Pepper Defense Enzymes Treated with Bacteria B4 and Actinomycetes A10The results showed that the mixture of B4 and A10 could induce the activities of pepper defense enzymes including PAL,POD,PPO,SOD and CAT.Appearing high peak of time and varieties of range were earler and higher than singly inoculating Phytophthora capsici.The variety range of activities of PAL,POD,SOD inoculatting the B4 +A10 were bigger than inoculatting B4 + A10+Phytophthora capsici.5.Studies on Colonization Trends of Bacteria B4 and Actinomycetes A10 on Pepper Root and soilThe results showed that B4 could colonize successfully in pepper root,and B4 and A10 had strong ablity of colonization in pepper rhizosphere.When inoculatting Phytophthora capsici,it could promote A10 to colonize in pepper root and control Pepper Phytophthora blight.The colonization ablities of B4 and A10 had no relationship with the measure of theirs inhibition zone.6.Studies on Action of Control Pepper Phytophthora Blight and Growth Promoting of Bacteria B4 and Actinomycetes A10The results showed that the biocontrol Bacteria B4 and Actinomycetes A10 could postpone outbreak time of disease,reduce disease index and circumstance,and promote pepper growth.The mixture of B4 and A10 could control pepper Phytophthora blight by 72.5%in greenhouse,and by 76.2%in the field after the strains were inoculated 11 days ago.B4 could improve the fresh weight and the dry weight of pepper by 44.1%and 36.2%in greenhouse, and by 81.5%and 69.6%in the field after the strains were inoculated 20 days ago.