Abiotic and biotic stress mitigation in rice using rhizospheric isolates for zinc solubilization

Rhizospheric bacteria play a critical role in plant health by enhancing nutrient availability, promoting stress resilience, and suppressing pathogens. This study aimed to isolate and characterize zinc- solubilizing bacteria (ZSB) from rice rhizosphere soils and evaluate their dual potential for biotic and abiotic stress management. Eighty-three bacterial isolates were obtained from 20 soil samples collected at the RPCAU Campus in Pusa and Dholi. Among these, 15 isolates demonstrated strong zinc solubilization ability, with 6 identified as Gram-positive and 9 as Gram-negative. Biochemical analyses revealed that 9 isolates exhibited catalase activity (top performers: I-44, I-60, I-74), 5 produced siderophores (highest: I-73), and 13 synthesized indole-3-acetic acid (best: I-6). In vitro assays showed that most isolates produced ammonia, and 7 strains (I-65, I-68, I-78, I-79) exhibited hydrogen cyanide production and antagonistic activity. Additionally, these isolates enhanced nutrient availability and demonstrated promising traits for stress mitigation. Strains I-6, I-61, I-65, I-67, I-73, I-78, and I-79 showed significant biocontrol efficacy against Helminthosporium, a major rice pathogen. This study highlights the dual benefits of ZSB in promoting zinc solubilization and providing integrated stress management, offering a sustainable approach to enhancing rice cultivation under both biotic and abiotic stress conditions.