| Strains of Actinomycetes and Bacillus against soil-borne pathogens were isolated from rhizosphere in vegetable bases in Fujian Province.Actinomycetes SC-33 and Bacillus YB-1 which have good antagonistic effect on soil-borne pathogens were screened and identified,fermentation conditions and Properties of intracellular antagonistic substance of actinomycetes SC-33 were studied.(1)Actinomycetes SC-33 and Bacillus YB-1 with a broad-spectrum of antagonistic activity were screen and identification for species:Actinomycetes SC-33 and Bacillus YB-1 were screened from 58 Actinomycetes or 70 strains of Bacillus spp.based on the dural culture method and filter paper diffusion method.The two strains were showed strong antagonistic activity on Fusarium oxysporum,Colletotrichum gloeosporioides,Sclerotinia sclerotiorum,Phytophthora infestans,and Botrytis cinerea,Pectobacterium carotovorum,Ralstonia solanacearum.Fermentation filtrate of the two strains also have antagonistic effect on second-juvenile(J2)of Meloidogyne enterolobii.Based on the culture traits,morphological characteristics,physiological and biochemical characteristics,and phylogenetic analysis based on 16SrDNA gene sequence and phylogenetic trees derived from Mrbayes analysis the actinomycetes strain SC-33 was identified as Streptomyces sp.and the bacillus strain YB-1 was identified as Bacillus methylotrophicus.(2)Pot experiments showed that Streptomyces SC-33 and Bacillus YB-1 have high effects on tobacco bacterial wilt disease suppression and growth-promoting effects:Control efficacy of Streptomyces strain SC-33 or Bacillus YB-1 against tobacco bacterial wilt disease was 60%and 40%respectively,while inhibition rate for root knot nematode disease was 40.05%and 70.12%respectively.The growth-promoting experiments showed that the 100-fold fermentation broth of Bacillus spp.YB-1 and Streptomyces SC-33 was found to have a promoting effect on the spinach seeds and cucumber seeds.(3)The liquid fermentation medium and suitable culture conditions of the Streptomyces SC-33 were studied:The suitable culture medium was selected through testing the antibacterial effect of fermentation broth to pathogen of F.oxysporum.The formula was:soluble starch 5g,corn flour 10g,Soy flour 10g,K2HPO4 0.5g,H2O 1000ml.The optimized fermentation conditions were:initial value 7.0,fermentation temperature 30℃,time 96-168 h,inoculum volume(v/v)4%,liquid volume 200ml/500ml.(4)Crude extracts of intracellular antagonistic substance of Streptomyces SC-33 were isolated and Properties of antagonist substance were studied.The results of antagonistic activity of solvent extract with five different polarity showed ethyl acetate extracts have strong antagonistic activity on many soil-borne pathogens.Ethyl acetate extracts showed strong antagonistic activity when keeping at the temperature below 40℃,stable in weak acidity and UV light irradiation for 45 min.The active substances were not sensitive to proteinase-K. |
