Integrating Drought-Tolerant Germplasm and Bacterial Endophytes to Improve Maize Performance under Water Deficit

Drought remains a major constraint to maize production, particularly in regions where water supply is uncertain. It affects plant growth by altering key physiological processes that lead to unpredictable yield losses. In this study, genetic variability among 25 maize genotypes was assessed under water-limited conditions, followed by an evaluation of bacterial endophytes in improving drought response under controlled conditions. Genotypes with distinct drought tolerance characteristics were screened under field conditions and selected based on morpho-physiological traits and drought susceptibility index. The drought-tolerant genotypes were further evaluated in a greenhouse factorial experiment with the interactions of Bacillus subtilis and Pseudomonas sp. under well-watered and water-deficit conditions. Significant variation (P < 0.05) was observed among genotypes, water regimes, and endophyte treatments. Grain yield was positively associated with ear diameter, thousand grain weight, and photosynthetic rate, while water use efficiency contributed to maintain performance under stress. Bacterial endophyte treatment improved root biomass, chlorophyll content, and photosynthetic activity, while reducing membrane damage under water-deficit conditions. Among the tested combinations, Bacillus subtilis with a tolerant genotype showed the most promising results. The overall performance of genotypes with endophytes interaction increased by up to 25% under water deficit. These findings highlight the combined role of genetic background and microbial association in shaping drought response. The use of suitable genotype together with beneficial endophytes may provide a practical option for improving maize productivity under water-limited conditions.