Screening of antagonistic actinomycetic strains and their inhibitions against Phytophthora infestans

In order to obtain highly effective and stably antagonistic actinomycetes strains against Phytophthora infestans,the inhibitory effects of living and fermentation filtrates of actinomycetic strains isolated from vegetable-grown soil on mycelial growth of P.infestans were detected with dual-culture and filter paper methods,and inhibitory manner,response to P.infestans,stability of inhibition effect after continuous passage culture,and influence on P.infestans mycelial morphological character were investigated in this experiment.The results showed that 17 of 74 strains were evidently antagonistic to P.infestans,but all of fermentation liquors of 17 strains were not antagonistic to P.infestans.Sy11 strain had response to P.infestans,and could produce and secrete some substances inhibiting P.infestans.After continuous passage culture for 25 times,the inhibitory rate of Sy11 strain on P.infestans still maintained over 81%.Sy11 strain could cause to lose original sketch and structure seriously.However,Sy11 strain just inhibited P.infestans but did not kill it.These results indicated that Sy11 strain might have a great potential in control potato late blight in future.