Screening And Identification Of Actinomycetes Antagonistic Against Cylindrocarpon Destructans

The 126 soil samples were collected from ginseng planting fields in Tonghua city,Jingyu county and Changbai county in Jilin province during 2006～2007.39 strains of fungi,68 strains of bacteria and 232 strains of actinomycetes were isolated from the soil samples.The variations of fungi,bacteria and actinomycetes populations in ginseng rhizosphere were also studied.The results showed that the microbal populations were decreased with the increasing planting ages.The variations of microbal populations between 5-year planting fields and replanting fields were more significant than the variations of microbal populations between preplanting fields and 1-year planting fields.The variations of microbal populations between 0～5 cm layers and 5～10 cm were more significant than The variations between 5～10 cm layers and 10～15 cm layers.But the same trend did not appear in the same layers of different ages planting fields.The antagonistic tests were carried out among the microbes which isolated from all the soil samples against Cylindrocarpon destructans.None of 39 strains of fungi had antagonistic effects against Cylindrocarpon destructans.Only 3 in 68 strains of bacteria had antagonistic effects,but the effects were not stable.9 in 232 strains of actinomycetes had antagonistic effects.The antagonistic tests were done again by the liquids.The best antagonistic catinomycetes called MS32 were screeninged,width of antagonists is 11 mm,Inhabiting rates is 76.45%.The liquid culture conditions of MS32 were primarily studied including medium,pH,temperature and time.After that the orthogonal tests were done.Eventually the optimal conditions were determined:the corn flour and bean flour medium,29℃,pH8,120h.The morphological observation and physical and biochemical characters were examined.The sequences of 16SrDNA were analysed.MS32 had the typical morphological characters of Streptomycetes.The results of physical and biochemical characters were the gelatine liquefication,no production of H₂S,no solidification and peptonization of milk,starch hydrolyzafion,Cellulose hydrolysis;It utilized D-glucose,D-xylose, D-fructose,sucrose,gossypose,inositol as carbon source.The length of 16SrDNA sequences were 1250 bp.Comparing with the high homological 32 strains of Streptomycetes in GenBank,the sequences of MS32 were the 98%similar as Streptomyces naraensis(AB184391).and the homology of 2 identified strains were also 98%.It indicated that the 4 strains might be the same species.