Study On The Biocontrol Of Sclerotinia Sclerotiorum By Antagonistic Actinomycetes

Sclerotium with the characteristic of soil-borne and aeroborne disease was one of the important rape disease. The higher resistant actinomycete strains were screened from rhizosphere soil and endophytic actinomycetes of chinese cabbage, Camellia sinensis, Ormosia hosiei and Ginkgo bilob. Meanwhile, the influence of rape seedling resistance by using antagonistic actinomyces. The coloniza-tion of actinomyces in soil, hylloplane of rape, and rape seeding was studied. And, indoor pot, leaves in vitro and field tests provided theoretical evidence for developping microbial manure.1. Isolation and screening of antagonistic actinomyces165 actinomycete strains were separated from rhizosphere soil and endophytic actinomycetes of chinese cabbage, Camellia sinensis, Ormosia hosiei and Ginkgo bilob.25 strains of the isolates were found suppressing Scleotinia sclerotiorum mecylium growth by pairing culture. Among them, YJ1, BC32, HD8 and CS4 with higher resistance were found. YJ1 was from the branch of Ginkgo bilob, and the other three were from soil. The inhibition zone wide of YJ1, BC32, HD8 and CS4 were 11,11,8 and 10mm. In the dual plate assays, and the anti-actinomycetes effect respectively reached 73.5%,84.4%,58.1% and 50.7% The germination of sclerotium and thecasporous were inhibited in high-concentration actinomycete liquid, but the antibacterial effect decreased in low-concentration actinomycete liquid.2. Identification of actinomycete strainsYJ1, BC32, HD8 and CS4 were classified as Streptomyces by morphological characters, cultural characters, physiological biochemical characters and 16S rDNA sequence analysis.3. Rape seedling resistance was increased by antagonistic actinomycesSOD,PPO and POD enzymatic activity of rape seedling increased markedly. There's no apparente quantitative relation among the three enzymes. In this experiment, the PPO enzymatic activity was lower, that maybe because of lower PPO content of rape seedling. The enzymatic activity increased higherly by YJ1 and CS4. As indicated by pot cultures, the results indicated that the four actinomycete strans significantly limited the enlargement of disease spots.4. Actinomycic prophylaxis effectThe result of laboratory test indicated using actinomycete liquid to daub rape leaves and spray leaves in vitro limited the enlargement of disease spots. The prophylaxis effect of HD8 was lower, agreeing with colonization and resistance experimental results. Leaves in vitro experiment showed that actinomyces had disease prevention effect and treating disease effect. Prophase of inhibitory action of BC32 was better than anaphase. In a field trial, the prophylaxis effect of YJ1 was the best.5. Actinomycic colonizationHD8 and CS4 could colonize in soil in short term. At the 40 days, the population of HD8 and CS4 were 107cfu/g and 104 cfu/g, and the population was trend to descend. The population of YJ1 and BC32 showed an increasing tendency in soil. The colonization ability of actinomyces on leaves was poorer. There's no marked HD8 and CS4 existent after 6～9d. BC32 and YJ1 were existing longer than HD8 and CS4 on leaves. It was found that actinomyces could be colonized in rape, and the number of thalline rises first and fall later. The number of root colonization was the most. The four actinomycete strains could colonize in rape by waterring root and soaking root.