Study On The Isolation, Selection And The Antagonistic Metabolites Of Soil Actinomycetes

This research took Gause's Synthetic medium as the separating medium. More than 400 strains of actinomycetes were separated from the soil collected form Shaanxi Yangling of China. One genetically stable strain J-129-08 was selected after comparison on inhibition activity to pathogenic fungi by means of selected in solied culture and fermental filtrate. Its metabolites had strong fungicidal activities. The main results were as follows:(1)By means of mycelium growth rate, spore germination and agar diffusion method, the fermentation broth of strain J-129-08 was tested against agricultural pathogen. The results showed that it had a certain degree of fungicidal activity. The results of the spore germination test showed that it had a great inhibitory effect to the Exserohilum turcicum (Pass.) Leonard et Suggs and Alternaria alternate.The inhibition rate were 92.8% and 83.2% respectively at the concentration of 600μg/ml. At the concentration of 300μg/ml, the inhibition rate could reach to 67.8% and 64.8%. The results of the pot experiment showed that its preventing and cure efficacy to Blumeria graminis could be 78.6% and 72.2%. However, it could get to 76.4% and 66.0% at a higher concentration.(2) The stabilities of strain J-129-08 and its fermented broth were tested.The results indicated that the secondary metabolites of strain J-129-08 was stable to acid and temperature when subculturing for ten generations. The fungicidal activity did not decrease.(3) By means of observation on substrate mycelium, aerial mycelium, spore and sporothrix, Cultural characteristics, Biochemical and physiological characteristics, strain J-129-08 was primarily identified as streptomyces and lavendlarectus.(4)Crude substances with biological activities were extracted from the fermentation broth of strain J-129-08 and its inhibition ability was tested .The results of mycelium growth rate method indicated that the extracted materials had an inhibition efficiency above 80% against Pyricularia grisea,Alternaria solani Sorauer,Gibberella zeae and Bipolaris sorokiniana (Sacc.)Shoemakey at the concentration of 1000μg/ml. It expressed the best inhibition activity against the mycelium growth of Pyricularia grisea.The inhibition efficiency could get to 90.8%. The results of the spore germination test showed that it had a great inhibitory effects to Pyricularia grisea,Bipolaris sorokiniana (Sacc.)Shoemakey and Alternaria alternate. The inhibition rate were above 80% at the concentration of 600μg/ml. The results of the pot experiment showed that its preventing efficacy to Blumeria graminis is good but not its cure efficacy.