| Continuous cropping obstacles is a common phenomenon occurred in facility agriculture.The accumulation of phenolic acids is one of the primary causes of continuous cropping obstacles in cucumber cropping.In protected cultivation condition,the continuous cropping of cucumber has become a norm and the content of ferulic acid?FA?has a obvious increase.when the accumulation level of FA exceeds the threshold,the growth of cucumber will be inhibited,even death.In this study,we isolated two bacterium strains which are able to degrade FA.Then we applied the inoculants which were made using the bacterium strains to the soil of continuous cropping and researched the specific mechanism of degradation of ferulic acid through the influences on cucumber development and enzyme activity of rhizosphere soil after applying the inoculants to the soil.The main results are as follows:?1?We isolated two bacterium strains which can degrade the FA efficiently and identified the bacterium strains using molecular biology techniques.One bacterium strain was identified as a actinomycetes named Gordonia terrae.CSY-F2 and the other one named Pseudomonas sp.CSY-F13 is a bacteria.We tried to alleviate the continuous cropping obstacles caused by FA using different kinds of microorganisms,which laid the foundation for developing the inoculants for degrading the FA.?2?The best degradation condition of Pseudomonas sp.CSY-F13 was 0.21g/L initial concentration of FA,6.61 initial PH of medium and 36.72°C of culture temperature,which was determined by the research.The degradation rate of FA was 82.77% after 6h and reached to 100% after 10 h under the beat degradation condition.Compared with other degrading bacteria,Pseudomonas sp.CSY-F13 has much greater degradation ability.Besides,the wide growth temperature and wide range of tolerant p H of Pseudomonas sp.CSY-F13 can lay the foundation for its applying in the soil.The optimum growth temperature of Gordonia terrae.CSY-F2 is 28°C.The main metabolite is 4-Vinylguaiaco1 when the FA is degraded by Gordonia terrae.CSY-F2.The conversion rate of 4-Vinylguaiaco1 reached up to 95.4% under 0.5g/L initial concentration of FA.In the process of degrading the FA by Pseudomonas sp.CSY-F13 and Gordonia terrae.CSY-F2,SOD,APX and other antioxidant enzymes in bacteria changed,which could lay the foundation for researching the degradation mechanism.?3?The inoculants made from Pseudomonas sp.CSY-F13 and Gordonia terrae.CSY-F2 were applied to the soil with exogenetic FA and then the physiological experiments were performed.The results showed that the contents of H2O2,O2.-and MDA in cucumber leaves were increased after adding FA to the soil,while the activities of CAT,SOD,APX and other antioxidant enzymes were decreased.The contents of H2O2,O2.-and MDA were lower and the activities of related antioxidant enzymes were higher in experimental group with FA and inoculants applied than that in treated group with only FA applied.Thus,we concluded that adding inoculants can effectively alleviate the stress caused by FA.?4?The activities of urease,alkaline phosphatase,sucrase and catalase in the soil of experimental group with Pseudomonas sp.CSY-F13 and Gordonia terrae.CSY-F2 applied were improved and the metabolism of soil organic matter were enhanced than that in treated group with only FA applied.Besides,the removal efficiency of harmful substances were also increased,which could remove excess phenolic acids and improve soil microbial consortia structure.Thus,Pseudomonas sp.CSY-F13 and Gordonia terrae.CSY-F2 could alleviate the stress induced by FA and were conducive to the growth of cucumber.In a conclusion,we isolated two bacterial strains named Gordonia terrae.CSY-F2 and Pseudomonas sp.CSY-F13 which have ability in degrading FA.Adding the strains in soil could improve the physiological indicators of cucumber under the stress caused by FA and repaire the soil with continuous cropping obstacles,which lay the foundation for the development of mixed inoculants used for degrading the FA. |
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