Preliminary Studies On The Fungicidal Activity Of Secondary Metabolic Products Of Streptomyces

912 colonies Streptomyces were obtained from 105 set of soil samples from Beijin and five provinces Guangzhou, Yunnan, Hunan , Sichuan, Xinjiang, on selective plates Gause 1 cultural medium.5 strains have antagonistic activity against Ralstonia solanacearum, 3 trains have antagonistic activity against Pyricularia oryzae, Phytophthora parasitica var. nicotiana. After preliminary screening tests, antagonistic activity of fermentation filtrates of those isolates were tested against several important plant pathogens including R. solanacearum, P. oryzae, P. parasitica var. nicotiana etc. Two stains, D35 and D12, were found to have stong antagonistic activity agaist R. solanacearum with inhibition zones of 12 mm and 8 mm respectively at 20 μLper plate. One strain , D39, was found to have stong activity against both Pyricularia oryza and Colletotrichum nicotianae, with mycelium grouth inhibition rates of 47.6% and 54.2% respectively at 3 mL per plate. In antibiotic test, the datum showed that the antagonistic Actinomyces extensive distribute in the soil, but the strongly antagonistic Actinomyces were few. D35,D12 and D39 isolated from Guangzhou, Hunan and Xinjiang , respectively, they were identified as Streptomyces.Optimum fermention conditions for D35,D12 and D39 were studied. According to the results, the best fermention condition as fellows: D12 is in the B-liquid medium shaked 60 hours; D35 is in the B-liquid medium shaked 48 hours; D39 is in the C-liquid medium shaked 72 hours.Three antagonistic Streptomyces optimum temperature and pH value are 27 ± 1 ℃ and 7.0, respectively. Meanwile, the optimum foster way was shaked all day.Results from greenhouse trial showed that the fermentation extract of D12 could drop down the disease percentage and disease index of P. parasitica var. nicotiana. The germination of rape seeds was promoted by the diluent of fermentation extract in the indoor environment test.