Global meta-analysis of drought associated rice rhizosphere microbiome data and soil application of selected bacteria reveals potential of Pantoea dispersa for drought stress alleviation in rice plants.

INTRODUCTION: Drought stress poses a significant threat to global rice productivity, jeopardizing crop yield and food security, particularly in water-limited agroecosystems. The application of plant-associated microbes to enhance drought resilience in crops has gained considerable attention in recent years. However, systematic investigation on changes in rice rhizosphere microbial diversity under drought stress remains limited. This study aimed to identify drought-responsive bacterial taxa and evaluate selected rice rhizosphere bacteria for their potential to enhance drought tolerance in rice. METHODS: A meta-analysis of 16S rRNA amplicon sequencing datasets from rice drought-associated studies was conducted to identify drought-responsive bacterial taxa. Based on the findings of meta-analysis and previous literature, five pre-isolated rice rhizospheric bacterial strains belonging to the genera Streptomyces, Burkholderia, Pantoea, Pseudomonas, and Variovorax were selected and characterized for key plant growth-promoting traits and osmotic stress tolerance using 25% of PEG. The selected isolates were subsequently evaluated for their potential to enhance drought tolerance in two Indian rice varieties, CR Dhan 802 (drought-tolerant) and Ranjit (drought-susceptible) under pot conditions. RESULTS: Based on meta-analysis of 16S amplicon datasets and literature review bacterial isolates possessing drought tolerance and plant growth-promoting traits, were selected for the pot experiments. Soil inoculation with selected bacterial strains showed that the treatment groups Pantoea dispersa NA-08, Burkholderia cepacia NA-07, and Consortium-I (S. jiujiangensis NA-06, B. cepacia NA-07 and P. dispersa NA-08) alleviated drought stress in both the rice varieties. Furthermore, these treatment groups showed significant enhancement in plant anti-oxidative and soil enzymatic activities. However, the treatments with Streptomyces jiujiangensis NA-06 and Variovorax guangxiensis NA-16 exhibited growth promotion in rice plants, but no significant alleviation of drought stress was observed. CONCLUSION: The isolate P. dispersa NA-08 showed the higher potential for enhancing rice drought tolerance in pot experiments and might serve as a promising isolate for evaluation under field conditions.