| Yam (Dioscorea opposita Thunb.) is monocotyledonous twining vine. Yam anthrax is a restrictive affect which restricts the growth and development of Chinese Yam. During early days of the laboratory experiments, we have isolated and screened Streptomyces 30702 from the rhizosphere soil of medicinal plants which resulted good inhibitory effects on the pathogen of Yam. In this study, we studied the biological control characteristics,field control effects and classification status of strain 30702 .The main conclusions are as following:(1) Strain 30702 produces plate confrontation effect of pathogen growth on Yam and its fermentation broth can inhibit the spore germination and hyphal growth.. At 10μg/mL spore concentration, the inhibition rate was 90.33%, but when the concentration was increased up to 100μg/mL, inhibit rate closed to 100%. Strain 30702 produces a variety of enzymes (chitinase, cellulase, ACC deaminase, proteolytic enzyme, beta glucanase) inhibit the growth of pathogenic bacteria. Strain 30702 has a broad spectrum of antibacterial activity against fungi and bacteria.(2) Strain 30702 has dissolved phosphorus, Siderophore production and promotion of Arabidopsis growth performance as an increase in the number of root hairs,longer root hairs length, healthy plant growth and results greenish leaf hypertrophy.(3) In vitro experiment, Strain 30702 disease index of Yam anthracnose inoculated bacteria reached 26.7%, inoculation of biocontrol strain 30702 leaves almost no sense of disease. Greenhouse experiment results showed that inoculated anthracnose of the healthy plant died after 14 days inoculation. Extraction of Yam anthracnose plantlets metabolites,LC-MS analysis found that inoculated pathogens, biocontrol plants and controled plants were compared, the body produced secondary metabolites. The field test results of Yam anthrax, using 30702 strains fermentation extracts control effects resulted better as compared to recommended control effects of pesticide concentration ratio .(4) The fermentation conditions of strain 30702 were optimized, to obtain the optimal fermentation medium for soluble starch 25 g/L,soybean powder 20 g/L,MgSO4.7H2O 0.6 g/L, CaCO3 0.2 g/L The fermentation conditions initial pH was 7.0, fermentation time 8d,fermentation temperature of 28℃， the solution of 30%. The wet weight of the fermentation product was 200.87g/L, the diameter of inhibition zone was 20.9mm, the wet weight and the antibacterial diameter were increased by 76.2% and 26.7% respectively. The results of this study not only increased the weight of mycelium of strain 30702, but also increased the yield of antimicrobial active substances.(5) The results of 16SrRNA molecular identification and specific primer PCR identification of strain 30702 was Streptomyces violaceoniger branch of actinomycetes, and evolutionary relationship revealed totally similar to Streptomyces malaysiensis CGMCC4.1900T similar rate of 97.75%. Secondly, for Streptomyces samsunensis DSM 42010T similar rate was 97.69%.(6) Strain 30702 substrate mycelium and gas hyphae grew well, aerial mycelium color grey white, later developed into black spore. Electron microscope sanning showed that many branches of aerial hyphae and hypha spore silk borned on the aerial mycelium found spiraland and the surface was not smooth. The morphological characteristics were similar to Streptomyces sp., which were consistent with the morphological characteristics of typical species in the evolutionary branching of Streptomyces violaceusniger 16SrRNA.Strain 30702 was different in physiological and biochemical characteristics and culture characteristics compared with Streptomyces malaysiensis CGMCC4.1900T and Streptomyces samsunensis DSM 42010 . Strain 30702 and strain DSM42010 performed well and grew best under the condition of 28℃ but poor growth was found at controlled conditions of 22℃-24℃. They resulted better growth under the temprature of 24℃-37℃.They could not grow under the conditions of 4 ℃-20℃ and above 40 ℃. The optimum growth temperature of strain CGMCC4.1900 was 28 ℃. Under the conditions of 22℃, the growth rate was poor . The growth rate was better under 24℃-37℃. Under 4℃-20℃ and above 40℃ could not grow. Strain 30702 was able to grow at a salinity of 7%, the strain DSM42010 was able to grow when the salinity tolerance was 5%, the strain CGMCC 4.1900 was able to grow at 4% and it could not grow when the salinity tolerance was 5%.So strain 30702 was better performinig under the salt tolerance of 7%. Strain 30702 were different in physiological and biochemical characteristics and culture characteristics compared with Streptomyces malaysiensis CGMCC4.1900T and Streptomyces samsunensis DSM 42010T. Strain 30702 grew poor on the media of ISP1 and DSMZ54. It prodeced yellow brown pigments on the cultured medium of M8. Strain CGMCC4.1900 produced yellow pigments in M8 and DSMZ54 cultured media. It grew poor in the cultured media of ISP1 and ISP7, the aerial mycelium was yellow green. Strain DSM42010 grew well in all of the above media. Aerial hyphae were found mostly gray colored. It produced brown pigment in M8 and DSMZ54 cultured media. Comprehensive analysis of morphological,physiological, biochemical characteristics of 16SrRNA gene sequence and other characteristics of the multi phase classification, preliminary identification of the strain 30702 helped in identifying a new species of Streptomyces sp. |
