Rhizosphere microbial diversity drives differences of peppers N absorption

Abstract

The rhizosphere microbiota is crucial for biogeochemical cycling and plant nutrient uptake, but the molecular mechanisms by which it influences pepper nutrient traits remain poorly understood. Using four cultivars (Yuanzhu pepper, YZ; bell pepper, BE; line pepper, LN; and horn pepper, HR), we investigated the relationships between rhizosphere microbial composition, CNP functional genes, and NPK uptake/allocation in pepper organs. YZ exhibited 15 % greater rhizosphere available nitrogen (N) than BE and 26 % more than LN and HR. Similar trends occurred for root total N content and rhizosphere soil abundances of nitrification genes (nxrA, amoA2) and dissimilatory N reduction gene (napA) across cultivars. Notably, the relative abundance of the N mineralization gene gdhA was significantly higher in YZ, while the ammonification gene ureC was elevated in both YZ and BE compared to other cultivars. Within the rhizobacterial co-occurrence network, YZ and BE also enriched specific functional microbes in modules (#3, #15). The abundance of these modules (included Arthrobacter, Leifsonia, o_Gaiellales, etc.) positively correlated with N-related gene abundance and significantly influenced pepper N nutrient content. This indicated that rhizosphere-recruited microbes significantly drive N availability differences among pepper cultivars. However, these rhizosphere-enriched microorganisms minimally affected phosphorus activation. Modeling analysis revealed that bacterial module abundance, N-functional genes, and soil N collectively explained 90.3 % (approximately 2.18-fold that for P content [41.5 %]) of the variance in pepper aboveground N content. This study enhances our understanding of microorganism-mediated N cycling across pepper cultivars.