| Fusarium wilt is the main soil-borne fungal diseases in cucumber productionseriously which affect the yield and quality of cucumber. Long-term use of chemicalpesticides to control had cause bacterial resistance, environmental pollution,hazardous substances residue and quality reduce, and restrict the sustainabledevelopment of cucumber production. Biological control is one of effective means tocontrol cucumber Fusarium wilt. The complex microbiological agents which cancontrol Fusarium wilt of cucumber; effectively included Bacillus subtilis (BacillusSubtilis) BSD-2, Actinomyces (Actinoplanes) S317, Trichoderma (Trichoderma) T36,had been developed on the base of the earlier study by Project group. This paperresearch on the function of the complex microbiological agents by exam the cucumberleaves defense response, the number of microorganisms and soil enzyme activitypatterns change, the diversity of soil microbial communities.We induced cucumber with BSD-2, S317and T36. Each one biocontrol strainsand the mix of three strains can reduce the incidence of Fusarium wilt and improvethe activity of polyphenol oxidase (PPO), catalase (CAT), β-1,3of glucanase andchitinase. The effect of compound of three strains was better than a single strain andcompound of two strains. The maximum activity of four defense enzymes was5.5times,0.9times,2.53times,3times higher than that of the control on the7th dayrespectively. It can be seen that compound of three strains can be significantlyincrease resistance and reduce the incidence of Fusarium wilt when it was applied oncucumber.The number of microorganism and enzyme activity in cucumber rhizosphere soilrelated with adding complex microbiological agents were researched. The resultsshow that: transplant seedlings when applied complex microbiological agents in thewhole growth period in cucumber, the number of microorganisms in the soil presentsa different dynamic changes.The number of bacteria and actinomycete showed a trendof increasing first and then decreasing afterward, complex microbiological agents oftreatment is always higher than the control group, the number of fungi and Fusariumoxysporum showed a trend of decreasing first and then increasing, complex microbiological agents of treatment is always lower than the control. The number ofbacteria in rhizosphere soil reached its maximum at fruit period; at flower period thenumber of actinomycetes reached its maximum, while fungi and Fusarium oxysporumreached its minimum. On the dynamic changes of soil enzyme activity takes on adifferent, the activities of catalase and urease had a similar trend of increasing firstand then decreasing, neutral phosphate enzyme activity decreased,while the sucraseactivity increased, but complex set of four kinds of soil enzyme activities in differentgrowth period is higher than the control group. But extend their effects of differentgrowth stages of cucumber with declining trend, visible, to achieve the desiredimprovement of complex microbiological agents and effect of soil community, youneed supplementation during the appropriate application.At different growth stages was applied to the complex microbiological agents,using the method of combining traditional microbiological analysis and molecularbiology (BIOLOG and DGGE), this study was influenced on soil microbialcommunity and enzyme activities of cucumber rhizosphere soil. Results showedthat appling complex microbiological agents at different growth stages can improvemicroorganism quanlities and soil enzyme activities. Complex microbiological agentsappended into seedling and flowering period were the most evident effect, comparedwith control, bacteria increase23.26%, actinomyces increases20.53%, fungi reducedby36%, Fusarium oxysporum reduced by40%; enhance its utilization ofmicroorganisms on carbon sources (AWCD), increase the functional diversity of soilmicroorganisms significantly (Shannon index). DGGE gel electrophoresis resultsindicate that the number and abundance of bacteria and fungi were notable increase.Indicates that the complex microbiological agents applied to increase the quantity ofrhizosphere bacteria and actinomycetes in soil, reducing the number of fungi andFusarium oxysporum, enhance the functional diversity of microbial communities.Meanwhile, Each period of treatment compared with the control, soil enzyme activityhave improved to varying degrees. Which applied at the seedling and floweringadditional compound microbial preparation was most obvious.Compared with thecontrol, urease, catalase, sucrase, neutral phosphatase enzyme activity increased by44.80%,71.61%,31.97%and32.28%respectively. The complex microbiological agents can improve the environment of the rhizosphere soil and promotemicroorganisms multiply.Mechanism of complex microbiological agents control of Fusarium wilt oncucumber, included improving activity of defense enzymes of cucumber, enhancingdisease resistance of plant itself; improving the microecological environment of soil,enhanceing soil enzyme activities, facilitating the plant’s absorption of nutrients in thesoil, conducivinge to robust growth of plants, and improved the capacity to resistdisease. The application of complex microbiological agents can improve themicro-ecological environment of soil and plants, can increase microbial diversity andtransform the structure to bacterial, which can reduces fungal diseases. |
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