Study On Actinomycetes Isolated From Soil And Their Antagonistic Activity Against Four Soil-born Diseases

This research focused on the soil samples collected from different vergetations. Actinomycetes with antagonistic activity against some soil-born pathogenic fungis such as S. Sclerotirem et al. were selected. Six strains were picked for pot trails and four of them were chosen for the morphologic character, culture characters and phenotypic characters tests. The main results are as follows:1. 107 samples were collected from Yan'an and Hanzhong Shaanxi Province. 145 strains of actinomycetes were isolated from them by dilution plate method.2. 154 strains of actinomycetes were screened for the ones with antagonistic activity against Sclerotinia sclerotiorem. The diameters of inhibition zone for 28 strains were more than 20mm, so these 28 strains were chosen for the next study.Four soil-born pathogenic fungis: Verticillium dahlia, Fusarium, oxysporum f.sp. cucumerinum, Phytophthora capsici and Sclerotinia sclerotirem were used for the secondary screening by growth rate method. The results were that: stains 1-1, 4-1, 9-6, 31-2, 35-2 and 104-1 possess high inhibition activity against pathgenic fungins offered. The inhibition efficacy of strain 104-1 against V. dahlia could reach to 90%, strains 1-1, 4-1 and 9-6 showed high activity against 3 pathogenic fungis, the inhibition rate of strains 31-2 and 35-2 reached to 100% and 90.83% respectively.Antibacterial spectrum of strains 1-1, 4-1, 9-6 and 104-1 were tested. Strain 104-1 have special activity against V.dahlia, the other three strains showed wide antibacterial spectrum. The inhibition rate of these three strains against Botrytis cinerea, Fusarium.oxysporum f. sp. cucumerinum, Phytophthora capsici, Magnaporthe grisea, Dothirella gregaria, Sclerotinia sclerotiorum were all higher than 90%.Tissue experiment showed that the inhibition rate of three fermentation broths against Sclerotinia sclerotirem were higher than 70%. The inhibition rate of strain 1-1 and 4-1 against B.cinerea reached to 50%.Pot trails of six strains against four soil-born diseases were also tested. Strain 104-1 showed the special inhibition activity against Verticillium dahlia, the control efficacy reached to 70% both in protection treatment. Control efficacy of three strains 1-1, 4-1, 9-6 against Sclerotinia sclerotirem, Fusarium, oxysporum f.sp. cucumerinum and Blumeria graminis were tested. The control activity against Sclerotinia sclerotirem were higher than 50% both in protection and cure treatment. Ten times dilution of strain 9-6 reached to 70% in pot trails. So 9-6 is worth of the next studies. Three strains have control effects to Fusarium, oxysporum f.sp. cucumerinum and Blumeria graminis. Strains 1-1, 4-1, 9-6, 31-2, 35-2, 104-1 all showed a considerable activity against Phytophthora capsici in pot trails except for 35-2.3 The morphologic character, culture characters and phenotypic characters of three strains were tested; the result indicated that three strains were all belong to the streptomyces.