| In agroecosystem,the soil microbiome performs a variety of ecological services such as mineralization of organic matter,nutrient cycling,and the promotion of plant growth.There is an increasing concern that the the long term over-used of chemical fertilizer has not only resulted in deteriorated soil quality but also led to large-scale ecosystem degradation,loss of productivity and decreasing microbial function.Bio-organic fertilizer can not only reduce the amount of chemical fertilizer,but also optimize the soil microbial ecological environment while improving the soil structure and fertility as well as crop yield.However,how bio-organic fertilizer altered the bulk soil microbiome and subsequently assembled the rhizosphere microbiome to enhance the crop yield in rotation system are still lack of research.Trichoderma guizhouense NJAU4742 was previously isolated in our lab and showed a significant ability to promote plant growth and control of soil-borne diseases.Bio-organic fertilizer produced by NJAU4742 has been used to control soil-borne diseases of different crops.However,the effects of continuous application of this bio-organic fertilizer on crop yield,soil microbiome and the further assembling effects on rhizosphere microbiome of different crops have not been determined.In the present study,pot experiment was conducted to evaluate the effect of different amounts of bio-organic fertilizer on maize biomass,and a six seasons field experiment in maize-cabbage-potato rotation cropping system was conducted to evaluate the yiled enhancement effect of this product.By the two consecutive seasons in the field of maize and cabbage,it was found that fertilization treatment and crop type functioned as decisive roles in the assembling of rhizosphere microbiome,but how fertilization affects the assembly of rhizosphere microbiome by changing the soil microbiome is still not clear.Then bulk and rhizosphere soils of the whole six seasons were investigated to analysis how application of the bio-organic fertilizer affect the assembly of maize-cabbage-potato rhizosphere microbiome through reshaping the soil microbiome,and the assembly mechanism of fertilization treatment and crop type on rhizosphere microbiome was clarified.Besides,the relationship between the characteristics of rhizosphere microbiome and crop yield was revealed in order to provide theoretical support for the construction of high-yield soil microbiome.The main results are as follows:1.Pot experiments showed that Trichoderma bio-organic fertilizer(BOF)efficiently promoted the growth of maize plant as compared to chemical fertilizer(CF)and organic fertilizer(OF).Field experiment showed that 6 seasons continuous applications of BOF effectively increased mean crop yields in maize-cabbage-potato rotation system by 18.30%,7.02%and 27.28%as compared to CF,and 15.81%,7.65%and 12.22%as compared to OF,respectively.Compared with CF and OF,the soil pH and the contents of OM,NH4+,AP and AK were higher in BOF.2.Two-seasons application of different fertilizers in the field experiment was selected to investigate the assembly effect of Trichoderma bio-organic fertilizer under maize and cabbage planting system.Results showed that the application of bio-organic fertilizer may enhance the growth promotion effect of Trichoderma and increase the abundance of potentially beneficial microbial consortia such as Cladorrhinum and Massilia.which were found to be highly correlated to improved crop yields.BOF resulted in significantly higher richness and diversity for bacteria and higher diversity for fungi as compared to CF,and preliminary found that both fertilization treatment and crop type were the major factors that impacted the composition of the rhizosphere microbiome.Besides,the key microbial consortia related to yield were predicted.3.In order to further clarify how fertilization affect the assembly of rhizosphere microbiome through soil microbiome,the effects of Trichoderma bio-organic fertilizer on soil and rhizosphere microbiome of rotation system(maize-cabbage-potato planting one season each year for two years)were then analyzed.In terms of rhizosphere bacterial community,similar to the conclusion of the two seasons,the assembly of rhizosphere bacterial community is determined by fertilization treatment and crop type.Compared to CF,the application of Trichoderma bio-organic fertilizer can improve the richness and diversity of rhizosphere bacteria community every season.Further study showed that the variation of soil bacterial diversity was consistent with that of rhizosphere.It was speculated that the application of bio-organic fertilizer could drive rhizosphere microbial assembly by changing soil bacterial community.Through the ternary analysis,correlation and heatmap analyses,BOF resulted in higher relative abundance of beneficial bacterial consortia,such as Paenibacillus and Pseudomonas,and increased with the planting season.Further analysis of the random forest model found that Paenibacillus and Pseudomonas was also enriched in the rhizosphere of different plants amendment with Trichoderma bio-organic fertilizer,and the relative abundances variation tendency of key bacterial consortia in the rhizosphere was significantly related to the soil.The mechanism of bacterial community construction in soil was studied by using phylogenetic information.It was confirmed that bacterial community construction was a decisive process selected by many factors,and soil pH and organic matter were the most important driving factors.4.In terms of rhizosphere fungal community,similar to the conclusion of two seasons,the assembly of rhizosphere fungal community is determined by fertilization treatment and crop type..BOF harbored the higher diversity of rhizosphere fungal community compared to CF.Further study showed that the soil fungal community constructed by application of bio-organic fertilizer significantly affected the alpha and beta diversities of fungal community.Through the analyses of LEfSe and heatmap,the application of bio-organic fertilizer induced higher relative abundances of Trichoderma,Aspergillus and Cladosporium,which were also the key beneficial fungi in rhizosphere.Through redundancy analysis,it was also found that pH and organic matter were important physicochemical factors affecting the assembly of fungal community.FUNGuild was adopted to analyze the nutritional pattern and ecological function of rhizosphere fungal community.Results showed that continuous application of bio-organic fertilizer increased the relative abundance of saprotroph and symbiotroph trophic fungi,and reduced pathotroph fungi.5.From the analysis of co-occurrence network combining bacteria and fungi communities,the application of bio-organic fertilizer induced more microbial ecological network dominated by fungi which revealed more complex composition,closer connection,and more active and frequent interaction between modules.Microbial community in bulk regulated by bio-organic fertilizer had legacy effects on rhizosphere in network composition and network connection,indicating that application of bio-organic fertilizer induced high-yield and high-efficiency rhizosphere microbiome by the regulation of bulk microbiome.In conclusion,both pot and field experiments showed that the application of Trichoderma bio-organic fertilizer promoted the plant growth and enhanced crop yields;through the comparative analysis of the data from the two and six planting seasons,it was found that fertilization treatment and crop type determined the assembly of rhizosphere microbiome.The application of bio-organic fertilizer driven the construction of microbial community by altering the soil pH and organic matter,and regulations of the formed soil microbial richness,microbial community structure,key beneficial microorganisms(Bacteroides,Pseudomonas,Trichoderma and Cladosporium,etc.)and network interaction characteristics all induced the assembly of high-yield maize-cabbage-potato rhizosphere microbiome. |
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