Symbiotic effectiveness of marked rhizobial and bradyrhizobial mutants in pea, pigeonpea and mungbean

The symbiotic effectiveness of rhizobial and bradyrhizobial mutants of the parent strains, namely, P5 Rhizobium leguminosarum bv. viceae), AO12 (Bradyrhizobium sp.) and MO5 (Bradyrhizobium sp.), resistant to streptomycin, kanamycin, erythromycin and sodium azide, was studied in aseptic conditions. The mutants isolated spontaneously were sensitive to their respective phages, RL1, VAR6 and MRV6 and were found to nodulate their host plants pea, pigeonpea and mungbean. Some of these mutants under reference (strl, eryl, kanl, azrl and azrl of P5; syrl, ery9, kanl6, azr9 and azrll of MO5 and strl, ery5, kanl, azrl, azr9 and azr l6 of AO12) exhibited significantly the increased values for the symbiotic traits (nodule number, nodule dry weight, plant dry weight and nitrogen content/plant) as compared to the parents. The azide resistant mutants of strains P5, MO5 and AO12 showed superiority over the parent strains as well as antibiotic resistant mutants for most of the symbiotic traits