Studies On Screening Of New Agricultural Antibiotics

The primary studies on screening of actinomycetes which metabolize the insecticidal, fungicidal and herbicidal components in soil have been carried out from May, 2001 to May, 2003. The main results are as follows:Taking Cause's Synthetic medium, Glucose Aspargine Agar medium, Arginine Glyceral salt Agar medium, Czapek medium and Gorodkowa medium as separating culture medium, 104 strains of actinomycetes were separated from the soil collected in 12 provinces of China.The activities of stomach poison and contact poison of the fermentation products of 104 strains were tested against the 3th instar larvae of Mythimna separata. The results showed that the fermentation products of 104 strains exhibited no insecticidal activity against the tested larvae.The herbicidal activity of fermentation extracts of 104 strains were tested against the Amaranthus retroflexus L. The results showed that only the fermentation products of No.24 had an intensive herbicidal activity against Amaranthus retroflexus L, and had an inhibition of 80.6% to taproot, an inhibition of 66.5% to caulis.By means of mycelium growth rate ,the fermentation products of 104 strains were tested against Botrytis cintrea, Fusarium graminearum, Alternaria longipes, Fusarium oxysporium, Exserohilum turcicum, F.oxysporium f.sp pumpkin, Glomerella cingulata Schr.et.Spauld, Macrophoma kuwatsukai, Alternaria solani. The results showed that thefermentation products of No.24, No.65, No.68 and No.102 had a certain degree fungicidal activity. The results of pot test indicated that the fermentation products of No.24, No.65 and No.102 exhibited 78.9%--84.3% of protective efficacy ,43.7%~76.1% of therapeutic efficacy.Eight fractions were isolated from the fermentation products of No.24 strain by bioassay-guided and Pre-HPLC. The fraction No.4 had the most intensive herbicidal activity, the inhibiting rate of No.4 was 95.8% , 93.76% and 86.36% against the taproot ,caulis and the bourgeon of Amaranthus retroflexus L respectively. The fraction of No.7 had the most intensive fungicidal activity. The diameter of inhibition zone was 2.4 centimeter against microzyme.By means of observation OD substrate mycelium, aerial mycelium, spore and sporothrix, No.24 strain was primaryly identified asStreptomyces.