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Study On The Effect Of Strong Reduction Of Soil Disinfection In Preventing And Controlling Soil-borne Diseases And Its Microbiological Mechanism

Posted on:2020-12-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:L L LiuFull Text:PDF
GTID:1360330578974206Subject:Physical geography
Abstract/Summary:PDF Full Text Request
Reductive soil disinfestation(RSD),consisting of incorporating soil with easily decomposable organic carbon,irrigating soil to the maximum water hold capacity,and covering soil with plastic film before planting,can not only effectively kill soil-borne pathogen,improve soil microbial community,but also repair the physicochemical property of degraded soil.Although a wide range of organic matters can be used for RSD,there is little information about the relationship between the characteristics of organic matters used in RSD treatment and their disinfestation efficiencies(DE).In addition,since the RSD-treated soil inoculated with pathogen still possess the ability to suppress disease and maintain crop health,the key disease-suppressive agents in the biotic and abiotic properties other than killing pathogens regulated by RSD are still unclear.Moreover,during the process of crop planting,the successions and driving factors of the pathogen and microbial community after RSD treatment under the influences of environmental changes and root exudates released by crop need to be further studied.Based on real-time quantitative PCR and Miseq amplicon sequencing,we performed the following studies,1)laboratory control experiment was used to investigate the differences of DE in the RSD treatment incorporated with different types of organic carbon and their influencing factors.2)heat treatment on the diseased soil and RSD-treated soil and pathogen or microbiota self/across reinoculation was used to study the key disease-suppressive agents in the biotic and abiotic properties regulated by RSD and their driving factors;3)the pot and field experiments were used to investigate the successions and driving factors of the pathogen and microbial community regulated by RSD under the cultivation of different crops(susceptible and non-susceptible to soil-borne diseases),and finally another pot experiment was used to verify these results.The main results were as follows:Laboratory control experiment showed that RSD treatments could effectively change the soil bacterial community diversity and decrease Fusarium oxysporum(F.oxysporum)populations in the soil,but DEs of the RSD treatments using different types of organic matter were dramatically different,such as DE in the RSD treatment incorporated with cellulose was only 30.6%,which significant lower than that in the RSD treatments incorporated with glucose(85.8%)and bagasse(72.3%).Content of easialy oxidized organic carbon(EOC)and total nitrogen(TN)in the organic matter had a significant positive correlation with the DE,and the ratio of total organic carbon to total nitrogen(C/N)had a significant negative correlation with DE.These results indicated that the incorporation of organic matter with higher EOC or lower C/N during RSD treatment could kill more pathogens.RSD-treated soil created an environment that was different from that of the diseased soil.Heat treatment and soil microbiota self-and cross-reinoculations resulted in the expansion of various soil microbial communities harbored by the two soil environments,but which had no significant influence in soil abiotic environment.Disease incidence(DI)of cucumber seedlings in the heat-treated RSD soil reinoculated with Rhizoctonia solani Kuhn(R.solani)(83.3%)was significantly higher than those in other RSD soils(0.0%-6.7%),indicating that the biotic properties of the RSD-treated soil may be directly responsible for disease suppression.Populations of R.solani in those heat-treated and microbiota self-and cross-reinoculated soils were approximately equal,whereas the DIs were dramatically different,indicating that the decrease in the abundance of soil-borne pathogens is not the sole determinant for disease suppression,and the soil abiotic factors also play an important role in disease suppression.The contribution rates of soil environmental factors to the successions of bacterial and fungal community were 36.8%and 8.0%,respectively;the contribution rates of reinoculated microbiota to the successions of bacterial and fungal community were 24.3%and 48.7%,respectively.These results indicated that soil environmental factors and reinoculated microbiota was the key driver for the reassembled bacterial and fungal community,respectively.The relative abundances of the bacterial genera Sphingobacterium and UC_Sphingobacteriaceae,as well as fungal genera Zopfiella,UC_Chaetomiaceae,and UC_Lasiosphaeriaceae,were negatively correlated with DI and positively associated with RSD-conditioned soil abiotic environment(pH and TOC),indicating that these potential disease-suppressive agents were highly dependent on soil environment.Furthermore,the verification test further showed that soil only inoculated with Zopfiella could not effectively suppress soil-borne disease,whereas the soil inoculated with Zopfiella accompanied by organic carbon amendment did.Pot experiment showed that the population of F.oxysporum significantly decreased by 99.22%at the end of RSD treatment,and the soil microbial community was also significantly changed.After planting watermelon that susceptible to fusarium wilt,the pathogen of F oxysporum in the RSD-treated soil resurged quickly and the soil microbial community changed to a similar status with the control soil,and the suppressive effect of fusarium wilt-disease index of watermelon in the RSD-treated soil was only decreased by 42.42%compared with control soil.Field experiment showed similar results with pot experiment after RSD treatment,such as the population of F.oxysporum significantly decreased by 99.45%and microbial community significantly changed.Notably,after the cultivation of non/less susceptible to fusarium wilt crops(celery and eggplant),the population of F.oxysporum in the RSD-treated soil was still significantly lower than that in the control soil by more than 95%.The bacterial community was gradually consistent with that of control soil,whereas the fungal community was still significantly different from that of control soil.In addition,the correlation coefficient between the dissimilarity in soil bacterial community and difference in soil pH was higher than that between the dissimilarity in soil fungal community and difference in soil pH.Therefore,it is speculated that crop types(plant root exudates and disease status)and soil environment changes may influence soil microbial community succession regulated by RSD.The verification results of pot experiment showed that rhizosphere soil microbial communities were dramatically different after planting celery,watermelon,and cucumber in rice and forest soils.The contribution rates of soil environment to the assembly of rhizosphere soil bacterial and fungal community were 39.4%and 24.5%,respectively,and the contribution rates of crop type to the assembly of rhizosphere soil bacterial and fungal community were 21.9%and 17.2%,respectively.Moreover,the ratio of contribution value of crop type to soil environment was higher for fungal community(70.2%)than that for bacterial community(55.5%).In addition,although there were no significant effects on the assembly of rhizosphere soil microbial community when the watermelon and cucumber were inoculated with F.oxysporum,the relative abundances of some beneficial microbes were significantly higher than those in the rhizosphere soils of the plants without inoculating.These results indicated that crops inoculated with pathogens could change the components of root exduates and recruit some beneficial microorganisms to enrich in the rhizosphere soil,and then promote the crop growth.In conclusion,the addition of organic matters with higher EOC,TN,and lower C/N during the RSD treatment could kill more pathogens.In addition to the decrease in the pathogen abundance,the abiotic environment created by RSD is suitable for the colonization of some disease-suppressive microbial agents,which contributed to the disease suppression by RSD.Rational fertilization regime after RSD treatment would be beneficial to maintain soil environment and achieve the sustainable colonization of beneficial microorganisms that regulated by RSD.The soil environment determined the compositions of bacterial and fungal communities,followed by crop type,and thus optimizing the microbial community through regulating the soil physicochemical properties and available organic substrates could support plant growth and health.
Keywords/Search Tags:reductive soil disinfestation, organic carbon, disease-suppressive agents, microbial community, soil-borne diseases, soil-borne pathogens, soil environment, crop type
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