Ecology, Environment and Conservation Paper

INFLUENCE OF WEATHER PARAMETERS ON ACTIVITIES OF BACTERIAL POPULATION ASSOCIATED WITH RHIZOSPHERIC SOIL OF RICE CROP

Jupinder Kaur and S.K. Gosal

Abstract

Environmental alterations leads to fluctuations in the activities of soil microbial population, as different weather parameters affect microbial biota and their activities in rhizospheric soil of crop. An agroclimatic investigation was carried out to study the effect of weather parameters on activities of soil bacterial population in rhizospheric soil of rice crop. Rice crop was grown under field conditions and under temperature gradient tunnel which was maintained at 4-5°C higher temperature than open field temperature. Attempt was made to screen high CO2 and high temperature tolerant diazotrophic bacteria from rice rhizosphere. A total of 9 different nitrogen fixing bacteria were isolated from rhizospheric soil samples of rice crop grown under field conditions and under temperature gradient tunnel. Out of 9 isolates, 4 isolates were able to grow upto 20% concentration of CO2 and 1 isolate showed growth upto 60°C. Tolerance to high CO2 and high temperature was observed more in the bacteria isolated from rice grown under temperature gradient tunnel. Biochemical characterization of the isolates showed that all the isolates were catalase, oxidase and citrate positive whereas negative for indole and H2S production test. Most of the isolates were MR and oxidase positive whereas, all the isolates were found to be negative for VP test. Functional characterization of these isolates showed that the isolate RT2 had highest IAA production (31.65 μg/mL) after 5 days of incubation in the medium supplemented with trytophan. Five isolates were found to show siderophore production on CAS agar plates. Among these 9 isolates, one isolate showed P-solubilizing diazotrophic trait. The amount of ammonia excretion for the isolates was in the range of 1.13-3.75 μg/mL. The maximum amount of ammonia (3.75 μg/mL) was excreted by isolate RT5. The isolate RT2 was found to be the best isolate in terms of the functional characteristics and tolerance to high CO2 and temperature levels. Taken together, our results indicate that climate change drivers and their interactions 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.