A Antifungal Metabolite Of Trichoderma Virens And Its Inhibition Of Rhizoctonia Solani

Rice sheath blight is one of three serious rice diseases and caused by Rhizoctonia solani. R. solani can produce sclerotia, which can endure reverse, even extreme environmental conditions. Therefore sclerotia play a key role in the survival and transmission of the pathogen. Because of the characteristics of sclerotia, this disease also becomes one of the plant diseases which is most difficult to prevent and control in practice. Trichoderma virens strain TY009, which produced the metabolites inhibiting sclerotial formation of R. solani (AG 1-1A), was screened in our lab. On the base of previous work, we try to separate bioactive fractions from the metabolites and estimate the potential of T. virens strain TY009 as biological control agent.The result of inhibition of sclerotial development of R. solani strain HZ001 by metabolites of T. virens strain TY009 showed that inhibitory periods occurred before sclerotial development and during the initial of sclerotial formation. Once the sclerotia formed, the metabolites failed to inhibit sclerotial development. The antifungal activities of metabolites of T. virens displayed them could completely inhibit the colony growth of R. solani.Bioactivitiy of metabolites through different dialysis membranes with molecular weight Cut Off illuminated that bioactive fraction molecular weight of the metabolite of T. virens is less than 1000 Da in size. The crude extract obtained with ethyl acetate extraction and purified by silica gel Thin-layer chromatography contained three fractions (Rf_0.93 A, Rf_0.76 and Rf_0.43). The fraction with Rf_0.43 were found to be the active compound by bioactivity experiment. The ultraviolet spectra analysis showed that the biggest ultraviolet absorption peak of the active compound is located in 232 nm. The active compound was analized by highly performance liquid chromatography -Mass spectrometry(HPLC-MS) and its molecular weight was 674. Compared with other antifungal compounds obtained from Trichoderma spp., molecular weight of active compound seperated by us was biggest and maybe is a new one.By Studying effect of the metabolites of Trichoderma on variety of ascorbic acid of Rhizoctonia solani during sclerotial development, we find the metabolites could affected the ratio of reduced/oxidized ascorbic acid. It may be one of inhibitorymechanism for sclerotial formation. The result of parasitism of TY009 against the hyphae of R. solani demonstrated that TY009 showed a high degree of antagonism overgrowing R. solani and similar to biocontrol strains TC3(r. harziqnum) and NF^r. harzionum). The result of parasitism of TY009 against the sclerotia of R. solani showed TY009 has shown to be an efficient mycoparasite of R. solani. In Comparion with TC3(r. harzionum), T.G(T. asperellum) and NF9(r. harzionum), TY009 was able to reduce the germination of sclerotia in 40% after 15 days, and other strains were in 90 %. Therefore T.virens strain TY009 is regarded as a potential biocontrol agent against R. solani.