Construction And Manipulation Of Microbiota In Tomato Suppressive Soil

Tomato bacterial wilt,caused by Ralstonia solanacearum,is a destructive disease which seriously hinders the tomato production of world.Therefore,it is important to explore effective strategy for controlling the disease and decipher its control mechanism to maintain the development of tomato production.Deciphering the microbiota characters in the soil which can suppress the disease,studying the assembly process and suppression mechanism of the microbiota,and exploring the mechanism involved in the suppressive soils to resistant pathogen invasion will provide the important basis for manipulating the soil microbiome to pre-control and suppress the soil-borne bacterial wilt disease.This study evaluated the control effect of continuous application of bio-organic fertilizer on tomato bacterial wilt in tomato monoculture soil.Secondly,for exploring an effective strategy to control tomato bacterial wilt diseases in high disease incidence soil,control effect of fumigation combined with organic fertilizer on tomato bacterial wilt in high bacterial wilt disease incidence soil was conducted.After that,for exploring more effective strategy to control tomato bacterial wilt diseases in high disease incidence soil,control effect of fumigation combined with bio-organic fertilizer on tomato soil-borne disease in high disease incidence soil was conducted.Finally,the suppressive soil formed by long-term continuous application of bio-organic fertilizer was selected as a model suppressive soil to construct tomato rhizosphere for exploring the mechanism involved in suppressive rhizosphere microorganisms resisting Ralstonia solanacearum invasion.Real-time fluorescence quantitative PCR(qPCR),and high-throughput sequencing were utilized to explore 1)the characteristics of bulk and rhizosphere soil microbial communities regulated by continuous application of bio-organic fertilizers;2)control effect of fumigation combined with organic fertilizer on soil bacterial wilt and the effect of the combined strategy on soil microbiota;3)control effect of fumigation combined with bio-organic fertilizer on different soil wilt disease in high disease incidence soil,and the effect of the combined strategy on soil microbiota;and 4)to explore the mechanism involved in suppressive rhizosphere microorganisms resisting Ralstonia solanacearum invasion.The main research results are as follows:1.Control effect of continuous application of bio-organic fertilizer on bacterial wilt disease,and the subsequent effect on soil microbiota in the eleventh season of tomato continuous cropping field experiment were evaluated.Results showed that continuous application of bio-organic fertilizer effectively controled the bacterial wilt disease compared with non-fertilization control,organic fertilizer treatment and chemical fertilizer treatment.Continuous application of bio-organic fertilizer did not significantly change the richness and diversity of bacteria in bulk and rhizosphere soil samples,but altered the bacterial community composition.For fungi,application of bio-organic fertilizer significantly reduced the richness and diversity in bulk and rhizosphere soils.Further analysis showed that the bulk and rhizosphere soil bacterial community formed by continuous application of bio-organic fertilizer was significantly correlated with the bacterial wilt disease.The results of network analysis showed that the ecological network of rhizosphere bacterial community induced by bio-organic fertilizer was more complex and connection was more closely than chemical fertilizer and organic fertilizer treatments.Core microorganisms such as Achromobacter,Lysobacter and Chitinophaga which were related to disease suppressiveness in network and stochastic forest model were enriched in bulk and rhizosphere soils from bio-organic fertilizer treatment.The function prediction of rhizosphere bacterial community by PICRUSt showed that the bacterial community induced by bio-organic fertilizer application had stronger ability of antibiotic biosynthesis than other treatments.Consequently,the microbial community of bulk and rhizosphere soils that could control bacterial wilt disease was formed by continuous application of bio-organic fertilizer.2.Effects of fumigation combined with organic fertilizer application on the control of bacterial wilt disease in high incidence soil,and the subsequent effect of the combined strategy on soil microbiota were evaluated.The results showed that fumigation combined with organic fertilizer effectively controlled the disease.Before planting,fumigation had no significant effect on soil bacterial and fungal abundance,diversity and community composition.However,at harvest time,compared with organic fertilizer and single fumigation treatments,fumigation combined with organic fertilizer significantly reduced bacterial and fungal richness and diversity in bulk soil,and meanwhile significantly changed the bacterial and fungal communities composition in bulk and Rhizosphere soils.Further analysis showed that rhizosphere bacterial community was the key factor to directly and indirectly inhibit Ralstonia solanacearum and control bacterial wilt disease.In addition,Rhodanobacter,Terrimona and Chitinophaga were potential key taxa in disease suppression.Therefore,fumigation combined with organic fertilizer regulated bacterial composition and stimulated key bacterial taxa to suppress Ralstonia solanacearum,thereby controlling bacterial wilt disease.3.Effects of fumigation combined with bio-organic fertilizer application on the control of soil-borne disease in high incidence soil,and the subsequent effect of the combined strategy on soil microbiota were evaluated.The results showed that fumigation effectively controlled the tomato soil-borne disease incidence,and significantly suppressed Ralstonia solanacearum and Fusarium oxysporum in the soil during harvest time.Moreover,the disease incidence of application bio-organic fertilizer after fumigation was significantly lower than application of organic fertilizer.Before planting,compared with non-fumigation treatment,fumigation directly reduced Fusarium oxysporum abundance,and regulated the composition of soil microbial community.While further analysis showed that the bacterial community formed by fumigation combined with bio-organic fertilizer application was the key factor to suppress Ralstonia solanacearum and Fusarium oxysporum during tomato cultivation.Moreover,Ohtaekwangia,Chitinophaga,Olivibacter,Flavihumibacter,Flavobacterium and Terrimonas,which were negatively correlated with Ralstonia solanacearum and Fusarium oxysporum,were significantly enriched in fumigated soils.4.The ability and underlying mechanism of rhizosphere microbiota assembled by suppressive soil induced by bio-organic fertilizer application to suppress Ralstonia solanacearum invasion were evaluated.After Ralstonia solanacearum invasion,the rhizosphere microorganisms assembled by disease suppressive soil showed higher resistance to Ralstonia solanacearum than assembled by high disease soil;the richness and diversity of rhizosphere bacterial community significantly increased,while the value for fungi significantly decreased.However,no significan difference of the richness and diversity of rhizosphere bacterial and fungal community assembled by high disease soil was observed.Further analysis of key bacterial taxa revealed that Flavobacleriaceae,Gemmatimonadaceae,Paenibacillaceae,Pseudomonadaceae,and Xanlhomonadaceae were more abundant in suppressive rhizosphere soil than that assembled by high disease soil.Subsequent verification tests in laboratory proved that Paenibacillus,Diaphorobacter,Streptomyces and Achromobacter,had the ability to suppress Ralstonia solanacearum.Therefore,the study showed that rhizosphere communities assembled by suppressive soil could acquire stronger suppressiveness to Ralstonia solanacearum through bacteria response.In conclusion,continuous application of bio-organic fertilizer effectively controlled the bacterial wilt disease incidence,and fumigation combined with bio-organic fertilizer can effectively control the tomato bacterial wilt and Fusarium wilt disease in high disease incidence soil.The application of bio-organic fertilizer and/or fumigation can stimulate the relative abundance of key bacterial taxa and reduce the abundance of pathogens by regulating the composition of soil bacterial community.The rhizosphere microbiota assembled in the suppressive soil can effectively suppression the invasion of Ralstonia solanacearum through the response of key bacterial taxa.