Bioinoculants as a means of increasing crop tolerance to drought and phosphorus deficiency in legume-cereal intercropping systems.

Ensuring plant resilience to drought and phosphorus (P) stresses is crucial to support global food security. The phytobiome, shaped by selective pressures, harbors stress-adapted microorganisms that confer host benefits like enhanced growth and stress tolerance. Intercropping systems also offer benefits through facilitative interactions, improving plant growth in water- and P-deficient soils. Application of microbial consortia can boost the benefits of intercropping, although questions remain about the establishment, persistence, and legacy effects within resident soil microbiomes. Understanding microbe- and plant-microbe dynamics in drought-prone soils is key. This review highlights the beneficial effects of rhizobacterial consortia-based inoculants in legume-cereal intercropping systems, discusses challenges, proposes a roadmap for development of P-solubilizing drought-adapted consortia, and identifies research gaps in crop-microbe interactions.

Benefits of phosphate solubilizing bacteria on belowground crop performance for improved crop acquisition of phosphorus.

Although research on plant growth promoting bacteria began in the 1950s, basic and applied research on bacteria improving use of phosphorus (P) continues to be a priority among many agricultural research institutions. Ultimately, identifying agriculturally beneficial microbes, notably P solubilizing bacteria (PSB), that enhance the efficient use of P supports more sustainable cropping systems and the judicious use of mineral nutrients. In parallel, there is more attention on improving crop root P acquisition of existing soil P pools as well as by increasing the proportion of fertilizer P that is taken up by crops. Today, new lines of research are emerging to investigate the co-optimization of PSB-fertilizer-crop root processes for improved P efficiency and agricultural performance. In this review, we compile and summarize available findings on the beneficial effects of PSB on crop production with a focus on crop P acquisition via root system responses at the structural, functional and transcriptional levels. We discuss the current state of knowledge on the mechanisms of PSB-mediated P availability, both soil- and root-associated, as well as crop uptake via P solubilization, mineralization and mobilization, mainly through the production of organic acids and P-hydrolyzing enzymes, and effects on phytohormone signaling for crop root developement. The systematic changes caused by PSB on crop roots are discussed and contextualized within promising functional trait-based frameworks. We also detail agronomic profitability of P (mineral and organic) and PSB co-application, in amended soils and inoculated crops, establishing the connection between the influence of PSB on agroecosystem production and the impact of P fertilization on microbial diversity and crop functional traits for P acquisition.