Inoculation with Pseudomonas Thivervalensis and Variovorax Paradoxus Enhances Yield and Grain Quality and Alters Rhizosphere Microbiota in Cereal–Legume Intercropping System

Purpose Cereal-legume intercropping and inoculation with Plant Growth-Promoting Rhizobacteria (PGPR) have been extensively documented to impact crop performance and the rhizosphere microbiome. However, information on their combined effects is limited, and the influence of PGPR-inoculation of legumes on the rhizosphere microbiome of neighboring cereals remains unknown. This study examines how legume intercropping with or without PGPR inoculation affects yield, grain quality, and rhizosphere bacterial diversity in durum wheat and barley. Methods Field experiments were conducted using three cropping systems: cereal sole cropping (SC), intercropping with legumes (IC), and intercropping with PGPR-inoculated legumes (ICC), where legumes included fenugreek and clover inoculated with a PGPR consortium (Pseudomonas thivervalensis and Variovorax paradoxus). Results The IC system increased grain yield by 26% for durum wheat and 30% for barley compared to SC. The ICC system further enhanced yields by 34% and 41% for durum wheat and barley, respectively. High-throughput 16S rRNA sequencing revealed distinct changes in the rhizosphere bacterial communities in the ICC system, with 445 and 389 Amplicon Sequence Variants (ASVs) enriched compared to IC and SC, respectively. Dominant genera in ICC soils included Stenotrophomonas, Streptomyces, Pseudomonas, and Variovorax. Many of these taxa positively correlated with yield and quality parameters, with Streptomyces and Variovorax linked to increased yields, while Pseudomonas and Serratia were associated with soil health. Conclusions These findings demonstrate that cereal-legume intercropping, enhanced by PGPR inoculation, can significantly improve cereal yield and grain quality while enriching beneficial rhizosphere bacterial communities, highlighting a promising agroecological approach for sustainable agriculture.