Regulation Mechanism Of Leguminous Crops Rotation On Soil And Microbial Communities In Continuous Cropping Solanum Tuberosum L.

Potato(Solanum tuberosum L.)is the most essential "consumed as both grain and vegetable" crop in the semi-arid region of central Gansu Province.The gradual intensification of potato continuous cropping has led to severe ecological and environmental problems in the region’s farmland.Under this background,a number of studies have devoted to explore the impacts of rotation of different crops with potato on soil physicochemical properties,enzymes and microbial diversity.However,the interaction pattern between "yield-soil-microbial-metabolites" in the legume-potato rotation system is unclear.Therefore,exploring the effects of legume-potato crop rotation on soil physicochemical properties,enzyme activity,microbial community structure and function and metabolites has important scientific significance for improving soil quality,increasing potato yield and promoting healthy development of farmland in semi-arid region.Here,our study conducted a two-year legume and potato rotation experiment based on three-year potato continuous cropping field,aimed to analyze the response of soil physicochemical properties and microbial diversity to different mulching treatments and legume crop rotation,and to study the effects of legume-potato rotation on soil properties,potato yield and quality under mulching conditions.Meanwhile,the study also clarified the interaction patterns between "yield-soil-microbial-metabolites" in legume-potato rotation system via combining the analysis of soil microbial community and function and soil metabolite.The main results are as follows:(1)Potato-legume mulch rotation significantly altered soil physicochemical properties,increased soil alkaline nitrogen(AN),available phosphorus(AP),available potassium(AK),total carbon(TC)and total nitrogen(TN)contents.Pea rotation and broad bean rotation under mulching conditions favored the increase of fungal α-diversity and β-diversity,and increased the relative abundance of bacteria(such as Proteobacteria,Bacteroidetes,and Olivibacter spp.),as well as the relative abundance of fungi(Basidiomycota,Glomeromycota,Clonostachys and Humicola spp.),and altered the number of microbial differential species.Redundancy analysis(RDA)indicated that the main environmental factors driving microbial community changes under potato legume rotation were p H,electrical conductivity(EC),TN and AN.(2)Legume-potato rotation improved soil quality in continuous potato fields and had significant effects on potato root growth and tuber yield and quality.Pea and broad bean rotation increased soil p H,water content(SWC),organic matter(SOM),total phosphorus(TP),TN,TC and AN,as well as the activities of soil enzyme(catalase,sucrase,alkaline phosphatase,and urease).Compared with potato continuous cropping,The yield of potato increased by 25.13% and 28.38% under pea-potato rotation and broad bean-potato rotation,respectively.Moreover,legume-potato rotation significantly increased total root length,root surface area,root volume,root diameter,root tip number,root vigor,tuber starch and vitamin C(Vc)content of potato.Among the treatments,the best overall physicochemical properties were observed under the broad bean-potato rotation.(3)According to macrogenomic analysis of soil microorganisms,the dominant bacterial communities are Actinobacteria,Proteobacteria,Acidobacter,etc.;The dominant archaea communities are Thaumarchaeota and Euryarchaeota;The dominant fungi are Mucoromycota,Ascomycota and Basidiomycota.The rotation of leguminous plants significantly changed the composition of soil microbial communities.The broad bean-potato rotation significantly enhanced the relative abundance of Actinomycetes,Proteobacteria,and Nocardioides in the soil,reduced instead the relative mass of Acidobacteria,Curvularia,Blastomonas,and Rhizophagus.In view of metagenomic differential functional analysis,this study has uncovered three critical pathways: "carbon metabolism," "nitrogen metabolism," and "sulfur metabolism".In the "carbon metabolism" pathway,the ethyl malonyl pathway(M00373)and the hydroxybutyrate dicarboxylate cycle(M00374)of the broad bean-potato rotation were enhanced.In the "nitrogen metabolism" pathway,the changes in the abundance of functional genes in the broad bean-potato rotation line enhanced assimilatory nitrate reduction,dissimilatory nitrate reduction,denitrification,and nitrogen fixation.In the "sulfur metabolism" pathway,broad bean-potato rotation promoted the assimilation sulfate reduction pathway.(4)Non-targeted metabolomics study found that soil metabolites include mainly lipids and lipid-like molecules,organic heterocyclic compounds,organic acids and their derivatives,phenylpropanoids and polyketides,etc.Under pea-potato rotation,320 key metabolites were upregulated,and 76 were downregulated,which enriched in metabolic pathways such as ABC transporters,purine metabolism,phenylalanine metabolism,galactose metabolism,etc.Under broad bean-potato rotation,375 key metabolites were upregulated,and 48 were downregulated,which enriched in metabolic pathways such as ABC transporters,purine metabolism,pyrimidine metabolism,and flavonoid and phenylalanine biosynthesis.Differential functional pathways of metabolites and metabolite enrichment analysis were performed to uncover three important metabolic pathways of ABC transporter protein,phenylalanine metabolism and purine metabolism.Leguminous plant rotation increased the content of metabolites such as LSerine,Guanosine,Inosine,and Adenosine in ABC transporters,and the abundance of metabolites such as Guanine and Adenine in purine metabolism was significantly upregulated,and the number of metabolites in broad bean rotation was higher than that in pea rotation.(5)Spearman correlation and RDA analysis revealed that the main influencing factors of soil microbial communities are SOM,AP,TP,TN,soil catalase,sucrase,urease,alkaline phosphatase,etc.;Significant correlation between dominant soil microorganisms and metabolites indicate that these microorganisms may participate in the absorption and transformation of soil nutrients through a series of metabolic pathways.The results of PL-SPM showed that soil physicochemical properties,soil enzymes,and soil microbial communities affected positively yield,soil metabolites instead affected negatively yield.In summary,legume-potato rotation significantly improved the quality of potato continuous soil and altered the diversity and community structure of fungi.legumepotato rotation also improved soil physicochemical properties,enzyme activity and potato root growth,which in turn contributed to the increase of potato tuber yield and quality.The bean-potato rotation regulated the soil microbial community structure,significantly affected the functional genes related to carbon,nitrogen and sulfur metabolism of important functional metabolic pathways,and reduced the abundance of potential pathogenic bacteria.Broad bean-potato rotation significantly affected the abundance of soil metabolites and important metabolic pathways such as purine metabolism and phenylalanine metabolism.