Superior symbiotic performance of native bradyrhizobia isolates over foreign inoculants with cowpea cultivars in India.

Efficiency of symbiotic interactions of native and foreign inoculants bradyrhizobia isolates with six cowpea varieties (CO1, CO3, CO4, CO6, Paiyur 1 and Vamban 1) were evaluated under field conditions. Based on sequence analysis of 16S-23S rRNA intergenic spacer (IGS) region, three native isolates were classified as B. yuanmingense . Cowpea varieties inoculated with bradyrhizobia showed significantly superior nodulation, nitrogenase activity, dry matter accumulation, and seed yield compared to uninoculated treatments. The native B. yuanmingense strains CR03 and CR09 exhibited host-cultivar specificity with CO3, and Paiyur 1, respectively. Plants inoculated with native B. yuanmingense isolates produced higher plant dry matter accumulation and seed yield compared to foreign B. japonicum inoculated plants. Correlation coefficients analysis revealed that plant dry matter accumulation emerged as the best criterion for selection of effective cowpea-bradyrhizobia associations in given physical and biological conditions.