Identification Of Two Antagonistic Microorganisms Towards Fusarium Wilt Pathogen Of Cucumber And Their Effects On Soil Microecology

Fusarium wilt of cucumber, which is caused by soil born fungi Fusarium oxysporumf.sp.cucumerinum Owenis, is now a common disease in most cucumber planting area. It causes seriouslosses of cucumber production. The effective control of this disease has become an urgent problem.Recently, biological control using antagonistic microorganisms attracts much more attention, because itis effective in the control of the disease and without pollution to the environment. It is beneficial to thesustainable development of agriculture. Two antagonistic microorganisms, strain2-17and2-22, wereisolated by the environmental microbiology laboratory, Zhejiang Academy of Agricultural Sciences. Inthis study, these two microorganisms were identified. The effects of different soil pH, moisture contentand different kinds and concentrations of nitrogen fertilizer on the proliferation of Fusarium wiltpathogen of cucumber were studied. The effects of antagonistic microorganisms on the control ofFusarium wilt pathogen, soil microorganism quantity and enzyme activities were evaluated usinglaboratory and pot experiments. The results are as follows:1.Strain2-17and2-22were identified and designated as Aspergillus sp.2-17and Hypocrea sp.2-22, respectively, by PCR cloning and sequence of the18S rDNA.2. The effects of pH, moisture content and different kinds and concentrations of nitrogenousfertilizer on the proliferation of cucumber wilt pathogen were studied at a constant temperature of28℃.The results demonstrated that the pathogen proliferated quickly under the conditions of pH from3to5and soil moisture content of10%~30%. The fastest-growing of pathogen was found at pH3.0andmoisture content of15%~20%. Pathogen proliferated slowly when the soil pH was between7.0and9.0and the moisture content was between30%~35%. Nitrogenous fertilizer would increase the proliferationrate of the pathogen in soil, especially application of3.70g/kg soil ammonium sulfate (ammoniumnitrogen).3. The effects of strain2-17and2-22on Fusarium wilt pathogen, bacteria, fungi, actinomycesquantity and activities of soil catalase, invertase and urease, were studied using pot experiments. Theresults showed that strain2-17and2-22could effectively inhibit the growth of Fusarium wilt pathogen,increase the number of bacteria and fungi, and promote the activities of soil sucrose and urease. Theeffective control of pathogen proliferation in soil made these two strains to be potential useful antagonistic microorganisms. However, inoculation of these two strains reduced the number ofactinomycetes in the soil. The effects of strain2-17and2-22on the soil ecology should be furtherinvestigated.