| Soil sickness is one of the main obstacles to agricultural sustainable development.As an economically important vegetable,tomato(Solanum lycopersicum L.)is one of the most crucial greenhouse plants.However,soil sickness of tomato is common,which lead to an increase in soilborne diseases and decrease in tomato performance.Biochar is known to enhance soil physico-chemical properties,suppress plant disease and improve plant growth.Nevertheless,the mechanism is not clear.In this study,the mechanism of biochar reducing plant diseases was explored from the perspective of rhizosphere microbial community.Tomato Fusarium wilt was taken as the research object in this research.Firstly,biochar with better effects on growth promotion and disease control of tomato and its application dose were screened from different raw materials.The effects of biochar on tomato rhizosphere microbial community were determined by high-throughput sequencing and q PCR.Secondly,the effects of biochar on PGPR colonization in tomato rhizosphere were studied by root split and chemotaxis experiment.Thirdly,the relationship between biochar induced changes of rhizosphere microbial community and tomato Fusarium wilt resistance was investigated by plant-soil microbial feedback test.Main results of this study are as follow:(1)The dose of 1%(w/w)of biochar made from cucumber,eggplant,artichoke,bean,pepper and tomato straw was added to soil.We found that biochar made from pepper and artichoke straw improved growth and inhibit Fusarium wilt of tomato,and biochar made from eggplant straw inhibited growth and promoted Fusarium wilt of tomato(p < 0.05).Effects of biochar made from different straw on rhizosphere microbial community abundance were different.Biochar made from artichoke increased the abundances of rhizosphere bacteria and Pseudomonas spp.,decreased the abundances of rhizosphere fungi and Fusarium oxysporum f.sp.Lycopersici(FOL),whereas,biochar made from eggplant increased the abundance of rhizosphere FOL(p < 0.05).Miseq sequencing results showed that the effects of biochar made from different straw on rhizosphere microbial community structure were different.Biochar made from artichoke increased the relative abundances of Streptomyces,Pseudomonas,Ceratobasidium.and Ilyonectria spp.Spearman correlation analysis showed that the incidence of Fusarium wilt in tomato was negatively correlated with the relative abundances of Streptomyces,Pseudomonas,Ceratobasidium,and Ilyonectria spp.(2)We added 0%,1%,2%,and 3% dose of artichoke biochar to soil.The result showed that tomato susceptibility to FOL manifests an obvious U-shaped biochar dose/response curve and 1%of artichoke biochar had the potential to suppress Fusarium wilt caused by FOL in tomato,while improving plant growth.Effects of different doses of artichoke biochar on rhizosphere microbial community abundance were different.All doses of biochar increased the abundance of rhizosphere bacteria;1% and 2% biochar decreased the abundance of rhizosphere fungi;1% biochar increased the abundance of rhizosphere Pseudomonas spp.and decreased FOL abundance(p < 0.05).Miseq sequencing results showed that the effects of different biochar doses on rhizosphere microbial community structure were different as 1% biochar increased the relative abundances of Pseudomonas,Microbacterium,Neorhizobium and Chaetomium spp.(p < 0.05).Spearman correlation analysis showed that the incidence of Fusarium wilt in tomato was negatively correlated with the relative abundances of Pseudomonas and Microbacterium spp.(3)Chemotaxis and biofilm formation tests showed that biochar could effectively attract PGPR,but it was not conducive to the formation of PGPR biofilm.However,the root exudates of tomato planted in biochar amended soil significantly attracted PGPR and stimulated the biofilm formation.Furthermore,in the pot experiment,biochar location was spatially separated from the site of PGPR to further ruled out the direct adsorption of biochar in the pot experiment,and it still promoted the rhizosphere colonization of PGPR.These results indicated that biochar promoted the recruitment of PGPR in tomato roots by regulating metabolism of tomato.(4)Biochar inhibited the mycelial growth of FOL and reduced the survival rate of pathogen in pot culture medium in a concentrate-dependent way(p < 0.05).It suggested that biochar can inhibit FOL growth directly.Plant-soil feedback test suggested that rhizosphere biota from tomato amended with biochar suppressed Fusarium wilt disease and up-regulated the expression of defense-related genes(Glu B?Pin2?PR1a?PR3?LOX).In split-root system(biochar and FOL were added to different pots),sterilized soil decreased the tomato growth promoting and Fusarium wilt inhibiting ability of biochar,and inhibited the up-regulation effect of biochar on the expression of defense-related genes in tomato roots.It indicated that biochar improved tomato resistance to FOL by changing the rhizosphere microbial community.(5)The effect of biochar on gene expression in tomato root was analyzed by RNA-seq technique.Biochar up-regulated the expression of defense-related genes in tomato roots,but the increase was modest.LOXD,Sl JAZ2,MAPK3 and WRKY transcription factor were up regulated1-2 times.After pathogen infection,biochar induced the up-regulation of response genes relate to jasmonic acid(PIN2,AOS)and salicylic acid(PR-P6,NPR1).The result indicate that induced systemic resistance in tomato against Fusarium wilt by biochar amendment involves jasmonic acid and salicylic acid signaling.In conclusion,the results of this study suggest that effects of Biochar made from different straw on tomato growth,Fusarium wilt and rhizosphere microbial community abundance were different.1% artichoke biochar can enhance tomato growth and suppress Fusarium wilt.Artichoke biochar inhibit FOL growth directly and inhibit Fusarium wilt indirectly through changing rhizosphere microbial community structure and promoting the recruitment PGPR by tomato. |
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