Characterization of Mesorhizobium ciceri isolates from chickpea root nodules: A biochemical approach

Abstract

Root nodules of chickpea plants from 44 locations in Maharashtra and Madhya Pradesh were collected for isolating Mesorhizobium ciceri. Isolation involved direct inoculation on Congo Red Yeast Extract Mannitol Agar medium. Isolates underwent screening tests (Glucose Peptone Agar, Hofer's alkaline, Ketolactose agar) for authentication. 22 Positive isolates were further tested biochemically and enzymatically, revealing variability in reactions. While most isolates showed typical reactions for certain tests (e.g., citrate utilization, gelatin liquefaction), they varied significantly in others (e.g., starch hydrolysis, H2S production). Preference for glucose, sucrose, and mannitol as carbon sources was noted, with mixed reactions in the skim milk test. These findings underscore the importance of thorough screening during isolation to authenticate Mesorhizobium and highlight the metabolic and indeed genetic diversity among strains.