Comparative symbiotic effectiveness of Bradyrhizobium (Vigna aconitifolia) on heterologous hosts

An experiment was conducted under controlled conditions to evaluate the comparative symbiotic effectiveness of four legume host species modulated by Bradyrhizobium (Vigna aconitifolia), namely, Vigna aconitifolia, Vigna radiata, V. ungiculata, and Cyamopsis tetragonoloba. The rhizobia used for establishing the symbioses were a set of 15 phage resistant mutants of Bradyrhizobium (Vigna aconitifolia) strain MR67 and which was susceptible to a lytic phage MRV 67. Inoculated plants were grown for four days under sand culture supplemented with N-free nutrient medium. The three Vigna species established effective symbiosis with all the rhizobial cultures whereas clusterbean was not nodulated. The nodule morphology was distinguishable species wise. On mungbean and mothbean few rhizobial mutants showed significantly higher effectiveness whereas on cowpea four rhizobial strains were ineffective. Although, nodules/plant and nodule dry weight considerably varied among the three hosts, the symbiotic effectiveness was comparably same.