| Thirty-six isolates of Gliocladium virens were obtained from the soil in citrus garden.comparing their antagonistic ability against citrus green mold (Penicillium digitatum) ,G-26 was chosed for parental strain for UV-inducing.The strain UV-44was got from the mutants of G-26 after UV irradiation that possessed the stronger potential against P. digitatum.The biological characteristic of strain UV-44 was researched,including hyphal growth,conidia production and germination as well as stability and antibiotic spectrum of UV-44's fermented solution.The biocontrol experiment against P. digitatum was made with the living organism and the fermentation solution of UV-44.Treated with UV for 0.5 to 2.0min, conidia lethal rate of Gvirens G-26 strain increased significantly with the time. Irradiated for 3 minutes, the mortality reached 98.67%, for 5 minutes all spores would die. Among the 108 mutants ,UV-44's suppressive ability improved hightliest ,its relative suppression rate was 43.93% compared with which of parental isolate , G-26.G-26 and UV-44's hyphal growth and sporulation condition were still similar:30℃, pH5 and all day darkness.However,some difference of their germinal condition was observed. UV-44 grew more slowly than G-26, and its sporulation ability decreased. The results of study on some biological characteristics of UV-44 showed that the kinds of culture medium, temperature, pH value and culturing days could greatly effect the production of chlamydorespores-The condition fit for chlamydorespore production were 30℃, pH10, oat meal and shaking incubating for 13 days respectively. Themostability of UV-44's fermented lipuid was good. The inhibition rate decreased slightly with the increasing of treatment temperature at the range of 40-80 ℃,and decreased only by 16.71% when treated in 121 ℃. It was relatively sensitive to pH value:the inhibition rate changed greatly with the change of pH value,and the fermented solution in pH5 was the most effective one . It wasn't stable after long time's storing. Inhibition rate decreased greatly with the increasion of storing time,and decreased by 63.51% after stored for 60days. The suppression ability of its fermented liquid arrived the hightest level,after incubated for 8days.And the fitful temperature and pH value were30℃ and pH5 .We also fond that fermented liquid of UV-44 was more effective on soil borning disease than on air borning disease.And it was unantagonistic to bacteria used in this experiment After successive transfers of seven times on PDA, the mutants could maintain their properties well.Storing experiment in room temperature showed that every treatment could decrease fruits' rot rate in different degree.Conidia suspension 's relative control effect were respectively 83.90%, 81.47% and 67.54%, chlamydorespores suspension's were 29.99%, 48.77% and 52.80%, fermented liquid's were65.03 %, 61.12%and 58.78%. But they all were inferior to prochloraz.With the increasion of storing days ,thire relative control effect all decreased,and the effect of chlamydospore decreased most slowly.Multicomparison results showed that relative biocontrol effect of them were significantly different.UV-44 was potential in biocontrol of citrus green mold.
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