Abstract:
A total of eight acid tolerant strains of bradyrhizobia isolates from indigenous cowpea plants
grown in acid soil in Varanasi, Uttar Pradesh, India, were examined for their ability to
survive in soil and yeast extract mannitol broth at low pH levels. All these isolates survived in
acidic (pH 3.5-6.5) conditions. Survival capacity of rhizobia was higher in soil than in
nutrient medium at low pH 3.5-6.5 levels. Symbiotic effectiveness of these strains under
polyhouse conditions in sterilized soil of pH 4.5 recorded the highest and lowest symbiotic
characters for dry matter production and nitrogen improvement per plant in CR09 and CR20
inoculated plants, respectively. All the examined isolates showed variability in their
symbiotic performances. The strain found to be more tolerant to stress were more effective N2
fixers in symbiosis with cowpea cv. Paiyur1 under acid-soil conditions. Symbiotic variation
among different strains showed that there is potential to improve strain performance under
stress conditions.
