Rhizosphere Core Microbial Community Assembly Induced By Crop Rotation And Its Control Of Banana Fusarium Wilt Disease

Banana is a main cash crop in agricultural production and global markets.Banana Fusarium wilt disease,caused by soil-borne pathogen of Fusarium oxysporum f.sp.Cubense race 4(Foc 4),can have severe impacts on sustainable development in banana plantations.Deploying crop rotation to resistance to pathogen infection offers critical pathways through regulation of soil microbial community.Plant rhizosphere microbiome function as first protective layer for some pathogen invasion,and core microbiome play a key role in plant defense response with specific biological functions.So far,numerous studies have focus deciphering antagonistic microbial community during banana planting,very few studies have reported the variation of antagonistic microbiome in the rotation season and it is still unclear the origination of these beneficial microbiome.For example,a large number of rhizosphere beneficial microbiota induced by pepper in the rotation season whether can stable transfer to that next generation of banana season and effective suppress soil-borne pathogen remains elusive.Thus,a better understanding of crop rotation and banana host plant selects unique core microbiome for suppressing soil borne disease provides indispensable meaning in banana production.In this study,we used pepper-banana rotation and eggplant-banana rotation as rotation regime model to identified antagonistic unique microbiota induced by three different host plants including pepper,eggplant and banana.First,we explore the effects of rotation on soil microbial community assemble using real time PCR and amplicon sequencing method and monitored the dynamic succession of soil microbial community by temporal exchange spatial strategies as well as identified antagonistic core microbiome induced by pepper,eggplant and banana,respectively.Subsequently,we conducted a pot experiment to verified the suppression ability repeatedly for core microbiome induced by pepper and eggplant.Besides,characterization of microbial community in rhizosphere soil and bulk soil after rotation crop returned to the field and identification the core microbiome has been also performed.We further arranged separate greenhouse pot trials in combination with culture-dependent approaches to isolate and validate the core microbiome.Our main results are obtained:1.we conducted two-year field trials to explore the effects of rotation on the number of pathogen abundance and soil microbial community,as well as the response alterations for microbial community to rotation.We found that Pepper-banana and eggplant-banana rotations both induced a significant reduction in disease incidence and pathogen density despite spatiotemporal variation.Disease suppression was related to alterations in the community structure via increased microbe abundance and diversity driven by the rotation regime.The predictors of pathogen density strongly directly affected banana disease incidence,which was highly negatively impacted by the rhizosphere bacterial community structure.The genus of Pseudomonas,Bacillus,Gemmatimonas,Luteolibacter,Phenylobacterium and Chryseobacterium were recognized as a pepper-unique antagonistic core taxon,only Pseudoxanthomonas was referred to eggplant-unique antagonistic core microbiota in the rotation season that were later transferred to the next generation for suppressing pathogen.In contrast,Burkholderia,Formivibrio and Novosphingobium were specifically induced by banana plant itself in the banana season.Soil pH was the best factor connected with community structure and composition.2.we repeatedly conducted two-season pot trials to profile the effects of rotation on the number of pathogen abundance and soil microbial community,as well as the response alterations for microbial community to rotation.We found that Pepper-banana and eggplant-banana rotations both induced a significant reduction in disease incidence and pathogen density in the rotation season and banana season,and there was no significant effect between them.The genus of Bacillus,Enterobacter,Pseudomona,Paenibacillus and Phntoea were recognized as a pepper-unique antagonistic core taxon,in contrast,Chryseobacterium and Aeromonas was referred to eggplant-unique antagonistic core microbiota.Pepper-banana rotation significantly increased bacterial copy numbers while decreased fungal copy numbers both in the rotation season and banana season.The bacterial and fungal community structure in rotation treatments significantly differed from banana monoculture treatments in rhizosphere soil while had little variation in bulk soil.The predictor of bacterial community structure was the most important microbial factor to against pathogen invasion.Bacterial and fungal microbial community structure and composition was best explained by soil pH regardless of rhizosphere or bulk soil.3.we conducted greenhouse pot trials to explore the core microbiota reconstruction induced by rotation crop residues and its disease suppression effect.Compared to banana residues addition,significant decline in banana Fusarium wilt disease,pathogen density and increased banana biomass was observed in pepper and eggplant residues addition treatment.The genus of Klebsiella,Dokdonella,Pseudomonas and Formivibrio were recognized as a pepper-unique antagonistic core taxon,in contrast,Azohydromonas and Luteimonas was referred to eggplant-unique antagonistic core microbiota.The copy numbers of bacteria were significantly increased when pepper and eggplant residues addition,while that of fungi decreased significantly.Higher community richness and diversity indexes was observed in pepper residues of rhizosphere and bulk soil.Clear clustering of bacterial and fungal community structure by different residues addition was revealed and significant difference existed between bulk and rhizosphere soil.Structural equation modelling revealed that shifts in bacterial community composition directly affected the incidence of banana Fusarium wilt.The contents of available phosphorus and potassium was the best determined factor for community structure construction.4.To further validate the antagonistic functions of the unique amplicon-based pepper-unique microbiota,we randomly isolated 240 bacterial strains from the pepper rhizosphere soil from the pots.Overall,a total of 147 isolates were affiliated with Proteobacteria,41 isolates were affiliated with Firmicutes and 12 isolates were affiliated with Actinobacteria.In addition,we found that only 12%antagonistic efficacy was seen among strains,and only the genera Bacillus and Pseudomonas exhibited strong antagonism of FOC4,especially Bacillus velezensis,Bacillus subtilis and Pseudomonas aeruginosa.The strongest inhibitory effects on FOC4 were from B.velezensis,followed by P.aeruginosa while no antagonistic effect was found for the E.tabaci strains using fermentation broth and volatile organic compounds.Following comparisons with disease incidence,F.oxysporum density and biomass of banana plants,we found that P.aeruginosa and B.velezensis both effectively reduced the disease incidence,suppressed the pathogen and marginally promoted the growth of banana plants compared with E.tabaci and the control treatment;the higher the inoculation concentration was,the more significant the effect.Moreover,B.velezensis induced stronger disease suppression than P.aeruginosa.In addition,the suspensions of E.tabaci were not capable of suppressing F.oxysporum,even at 10~7 CFU/g soil.In conclusion,pepper-banana rotation and eggplant-banana rotation both induced a significant reduction in disease incidence and pathogen density under field and greenhouse pot condition.Shifts in rhizosphere bacterial community composition directly affected the invasion of pathogen.The genus of Pseudomonas and Bacillus were specifically induced by pepper and recognized as a pepper-unique antagonistic core taxon,only Pseudoxanthomonas was referred to eggplant-unique antagonistic core microbiota in the rotation season that were later stable transferred to the next generation for suppressing pathogen and was verified by a pot experiment.The suppression of F.oxysporum pathogen can likely be attributed to the antagonistic activity of core microbial strains fermentation broth and volatile organic compounds.