Rhizosphere metabolite dynamics in continuous cropping of vineyards: Impact on microflora diversity and co-occurrence networks

Abstract

The metabolism of the crop rhizosphere affects microflora diversity and nutrient cycling. However, understanding rhizosphere metabolism in suitable crops within arid desert environments and its impact on microflora interactions remains limited. Through metagenomic and non-targeted metabolomic sequencing of rhizosphere soils from one uncultivated land and four vineyards with cropping years of 5, 10, 15 and 20 years, the critical importance of rhizosphere metabolites in maintaining bacterial and fungal diversity was elucidated. The results revealed that Nocardioides, Streptomyces, and Solirubrobacter were the relatively abundant bacterial genera in rhizosphere soils, while Rhizophagus, Glomus, and Pseudogymnoascus were the relatively abundant fungal genera. The composition of rhizosphere metabolic changed significantly during the continuous cropping of grapevines. Dimethylglycine, Formononetin, and Dehydroepiandrosterone were the most important metabolites. Enrichment analysis revealed significant involvement of metabolic pathways such as biosynthesis of amino acids, unsaturated fatty acids, and linoleic acid metabolism. Procrustes analysis highlighted stronger correlations between rhizosphere metabolites and bacterial community compared to those of fungal community. This suggests distinct responses of microflora to crop-released chemical elements across different soil habitats. Co-occurrence network analysis demonstrated complex associations between rhizosphere metabolites and soil microflora, the positive correlations between rhizosphere metabolites and microflora networks predominated over negative correlations. Partial least squares path model indicated that the effect of cropping years on rhizosphere metabolites was greater than that on bacterial microflora diversity. Futhermore, pH, total phosphorus, and alkali-hydrolyzed nitrogen were the key environmental factors affecting rhizosphere metabolites and microbial diversity. These results deepen our valuable insights into the complex biological processes that rhizosphere metabolites influence on microorganisms, and provide strong support for maintaining microbial diversity in farmland soils in arid regions.