Isolation And Screening Of Endophytic Actinomyces From The Wild Plants

Endophytic actinimycetes were isolated from the wild plants harvested from QinLing for finding new strains in biological control. The isolates had been assayed for colonization, antagonistic activity, activity of fermentation broth in vitro, optimized fermentation conditions, the biological characteristic and greenhouse experiment. The strain SG2 was identified. So new strains could were offered for improvement and preparation exploitation of biocontrol.The result showed that twenty-nine strains of endophytic actinimycetes were isolated from the wild plants, gained more from pink (Dianthus chinensis) and wild soybean (Glycine soja). The isolates quantity was more in root than leaf and stem of plant, different strains quantity was acquired in different media, S-medium was excellent. The treatment method of sample tissue was better than rubbing sample.The surface-sterilized effect with sterile water, existent test and colonization were studied to validate endophytes. The result indicated that twelve strains were endophytic actinomycetes and could colonize in plant they were in different family and different genus with host plants.Antagonistic activity test in vitro found that six strains had significant inhibiting effect 88.0% inhibiting rate could be gained to Botrytis cinerea by strain SF20, The fermentation filtrate of SG2 metabolites was detected to have stronger antagonism against Alternaria solani, inhibiting zone got 35mm. The strain SG2 fermentation filtrate suppressed on conidia germination of pathogens, 100% inhibiting rate could be gained to Botrytis cinerea, Fusarium oxysporum f.sp. niveum, Fulvia fulva, Alternaria solani, Verticillium dahliae.Optimum fermentation condition test for strain SG2 showed fittest carbohydrate was dextrose, nitrogen compound was bean flour, optimum fermentation time was 7d, optimum fermentation temperature was 26℃,fittest inoculum quantity was 10%, fitting ferment pH was 7.0, fittest media volume was 50ml·250mL-1.The biological characteristic studies of six strains showed that they had different effect on growth of cucumber, tomato and soybean. Actinomycetes suspension of strain SF4 and SF20, ferment broth of strain SF19 could promote seed germination and plant growth. Strain SF20 and strain SF4 also increased Chlorophyll quantity in cucumber and tomato leaves.The study on control fungal diseases in the greenhouse found that 89.72% and 73.27% of control effect to Alternaria solani were obtained by ferment broth of strain SG2 and strain SF20, and 89.61% and 78.08% to Sphaerotheca fuliginea were acquired by strain SF4 and SF20. The result also showed control effect of ferment broth on diseases was better than actinomycetes suspension'.Strain SG2 was identified to Griseofuscus group, the species of Streptomyces albidofuscus on the basis of the morphological features, cultural, physiological & biochemical characteristics and the phylogenetic analysis of 16SrDNA.