Beneficial bacteria mitigate combined water and phosphorus deficit effects on upland rice

Limited water and phosphorus availability are major challenges in upland rice production. Plant–microbe interactions, especially with beneficial bacteria, have shown promise in mitigating these stresses. This study investigated the influence of microbial inoculants with hydration-promoting and phosphorus-solubilizing abilities on upland rice yield under drought and phosphorus deficiency.

Upland rice (BRS Esmeralda) plants were grown in a greenhouse with different water availability conditions (well-watered and drought), phosphorus levels (normal 200 mg dm⁻³ and low 20 mg dm⁻³), and microbial treatments (no-microorganisms and single isolates, Serratia marcescens strains BRM 32114 and BRM 63523, and combined isolates Bacillus toyonensis BRM 32110 + BRM 32114 and BRM 63523 + BRM 32114). Root and shoot traits, as well as production components, were analyzed.

While the microbial treatments affected the roots, the larger effects were seen in the shoot rice plants. When both water and phosphorus were limited, grain yield decreased significantly. However, plants inoculated with beneficial bacteria showed a substantial increase in grain yield (average of 39.5% in 2019/2020 and 18.8% in 2020/2021) compared to uninoculated plants under combined stresses. This increase was especially pronounced in plants treated with BRM 63523 (strain) alone or combined with BRM 32114 (strain). These inoculated plants also showed improved photosynthetic activity (average increase of 24.6%), which may have contributed to the higher grain yield.

Inoculating upland rice with specific Serratia strains effectively increased shoot and root traits under combined water and phosphorous stresses. These findings highlight the potential of plant–microbe interactions for sustainable upland rice production.