Influence of Environmental Factors on Activities of Bacterial Population Associated With Rhizospheric Soil of Wheat Crop

Abstract

Aim: To study the effect of environmental factors on the activities of soil microbial population in the rhizospheric soil of wheat crop. Study Design: An agroclimatic study was carried out to study the effect of environmental alterations on the activity of soil bacteria in a multifactor climate change experiment in which wheat crop was grown under field conditions and under temperature gradient tunnel maintained at different and higher temperature. Attempt was made to screen high CO2 and high temperature tolerant diazotrophic bacteria from wheat rhizosphere. Place of Study: Department of Microbiology, PAU, Ludhiana. Methodology: Nitrogen fixing bacteria were isolated on Jensen’s medium using serial dilution spread plate technique. The bacterial isolates were characterized biochemically using standard techniques as described in Bergey’s Manual of Determinative Bacteriology.The isolates were also assessed for their ability to produce indole acetic acid, siderophores production, ammonia excretion, qualitative phosphate solubilization and solubilization of phosphate by quantitative method. Results: A total of 21 different nitrogen fixing bacteria were isolated from rhizospheric soil samples of wheat crop grown under field conditions and under temperature gradient tunnel. Out of 21 isolates, 8 isolates were able to grow upto 20% concentration of CO2 and 7 isolates showed growth upto 60°C. Tolerance to high CO2 and high temperature was observed to more in the bacteria isolated from the rhizospheric soil of wheat crop grown under temperature gradient tunnel. Functional characterization of these isolates showed that the isolate WT5 had significantly higher IAA production (44.3 µg/ml) after 5 days of incubation in the medium supplemented with tryptophan. Among these 21 isolates, six were found to have P-solubilizing diazotrophic trait and five were found to show siderophore production on CAS agar plates. The amount of ammonia excretion was non-significant among the isolates and was in the range of 1.14-3.70 µg/ml. The isolate WF6 was found to be the best isolate in terms of the functional characteristics and tolerance to high CO2 and temperature levels. Conclusion: Results indicate that alterations in environmental factors may cause changes in activities of bacterial populations. These results illustrate the potential for complex community changes in terrestrial ecosystems under climate change scenarios that alter multiple factors simultaneously.