Selection and characterization of effective Azospirillum isolates from rice field of Chhattisgarh plain

Abstract

Twenty-two soil samples were collected from farmer’s field of Bilaspur district for isolation & enumeration of Azospirillum bacteria. Out of these 13.64% soil samples lacked Azospirillum. Based on a population threshold of ≥2 × 10⁴ g⁻¹ of soil, 9 samples were selected for further physiological characteristics and performance assessments. These 9 local isolates were compared with a state check under both laboratory and pot conditions. The selected Azospirillum isolates, including the state check, were tested for different salt concentration, temperature, and pH tolerance under in vitro conditions. All isolates tolerated up to 3% salt concentration. The optimal pH range was 7-8, with 8 out of 10 isolates (excluding Azs-02 and Azs-03) tolerating pH 5-8, but none could withstand pH 4. In terms of temperature, all isolates grew between 20 °C and 40 °C, while only Azs-05 and the state check could tolerate 50 °C. Pot experiments evaluating Biological Nitrogen Fixation (BNF) parameters—such as plant height, grain per panicle, yield, and nitrogen uptake—identified local isolate Azs-13 as the most efficient among all isolates, including the state check. Thus, Azs-13 is suggested as the most potent nitrogen-fixing strain for rice cultivation in the Chhattisgarh plains.