Isolation and Screening of Azotobacter spp. for Plant Growth-Promoting Properties and Their Survival under Various Environmental Stress Conditions.

Abstract

This study explores the isolation, screening, and characterization of Azotobacter spp. for their potential as plant growth-promoting bacteria (PGPB) and their resilience under various environmental stress conditions. Azotobacter spp. are recognized for their ability to fix atmospheric nitrogen, produce phytohormones, solubilize phosphates, and secrete siderophores, thereby enhancing soil fertility and plant growth. Soil samples were collected from diverse agricultural sites and used to isolate Azotobacter strains on selective Ashby’s mannitol agar medium. The isolated strains were subjected to a series of biochemical tests for genus confirmation. Subsequent screening focused on key plant growth-promoting traits, including nitrogen fixation capacity, production of indole-3-acetic acid (IAA), phosphate solubilization, and siderophore production. These properties were quantified using standard microbiological and biochemical assays. The selected Azotobacter strains were then exposed to various abiotic stress conditions such as temperature extremes, salinity, pH variations, and drought to evaluate their survival and functional efficacy under stress.Results indicated that several Azotobacter strains not only survived these stress conditions but also retained significant levels of their plant growth-promoting activities. Specifically, strains exhibited robust nitrogen fixation, consistent IAA production, effective phosphate solubilization, and continued siderophore secretion despite environmental stresses. Pot experiments with wheat plants under controlled conditions further demonstrated that these resilient strains could significantly enhance plant growth parameters, such as shoot and root length, biomass, and chlorophyll content, under stress conditions.The findings underscore the potential of Azotobacter spp. as effective bio-inoculants to improve crop productivity, particularly in stress-prone environments. This study highlights the importance of selecting stress-tolerant strains for sustainable agriculture, given the increasing incidence of environmental stress factors due to climate change. Future research should focus on large-scale field trials and the development of formulations to harness the full potential of these beneficial strains in diverse agricultural settings.