Isolation and characterization of antibiotic and antimetabolite resistant mutants of Rhizobium sp. and their symbiotic interaction with Sesbania aculeata L.

Abstract

A native rhizobial strain {Rhizobium sp.) nodulating dhaincha {Sesbania aculeata L.) was isolated, and designated as RS-02. The sensitivity of RS-02 strain was studied against two antibiotics (Streptomycin and Rifampicin) and one antimetabolite (Sodium azide). Spontaneously occurring antibiotic / antimetabolite resistant mutants were isolated and designated as Str, Rif and Azi respectively. These resistant mutants were examined for their physiological characteristics (carbon and nitrogen utilization), cross resistance to each other and symbiosis with the host plant dhaincha. The parent strain along with resistant mutants were tested for their nodulation and symbiotic nitrogen fixation traits. It was found that all the mutant strains were able to infect dhaincha roots. The effectiveness of the marked rhizobial mutants in dhaincha exhibited a significant difference in symbiotic traits.