Screening,Identification Of Two Strains Of Streptomyces Antagonizing Plant Pathogens And Study On The Fermentation

The research for biocontrol microbe resources from actinomycetes is a hot topic at present.In this study,five species of important plant pathogens were used as targets to screen actinomycetes that isolated from soil and shrimp shells.Two strains with good inhibition effect were screened from 115 isolates.Their inhibition properties and fermentation conditions were studied.Hope to lay the foundation for the further development and utilization of actinomycetes.The main results are as follows:1.115 actinomycetes were obtained from soil and shrimp shells samples by using the different pretreatment and spread-plate methods.2 strains of Streptomyces with good inhibition effect were selected after twice screening by using plate confrontation method and combining with other factors.2.Two strains of Streptomyces spp.were identified as S.hygroscopicus(No.F4)and S.reticuli(No.Y12)respectively by analyzing the data of colony growth morphology,electron microscopic morphology,sequence alignment,phylogenetic tree and physiological-biochemical techniques.3.PSA medium was used to determine the inhibition rate of two strains Streptomyces against five plant pathogens by using method of the plate confrontation.By investigating the effect of inoculation time and the type of the medium on its antifungal properties,the inhibitory rate of two strains of Streptomyces was determined by setting 5 sorts of media and 5 inoculation time gradients.The results showed that the best inhibition medium for Streptomyces strains F4 and Y12 was Sabouraud and Oat respectively(The inhibition rate of strain F4 was 73.33%,The inhibition rate of strain Y12 was 53.33%).When two strains of Streptomyces were inoculated 0-4 days in advance,the inoculation time was positively correlated with the inhibition rate.Finally,through the different experiments of these two factors,it was concluded that the growth state of Streptomyces is positively correlated with the inhibition activity.4.It was determined that the medium L5 was the optimal formulation of 2 strains of Streptomyces,temperature 30℃,pH=8,inoculation size 5%and fermenting for 4 d were optimal conditions by liquid fermentation single factor experiment.The inhibition activity of the fermentation broth was measured by using a moisturizing culture method.The results showed that the fermentation broth of Streptomyces strains F4 and Y12 had inhibition rate of 63.32%and 98.94%against Botrytis cinerea respectively.5.11 kinds of solid-state fermentation medium were used to screen the solid fermentation medium formulation suitable for growth of Streptomyces strain Y12,and different inoculation methods were tests through the examination of solid fermentation capacity.The results showed that the medium of sand rice flour was suitable for the growth of Streptomyces strain Y12.Inoculation with bacterial suspension can increase the yield of Streptomyces fermentation.