Symbiotic Effectiveness of Different Antibiotic Resistant Mutants of Moth bean (Vigna aconitifolia) Rhizobium MR 67

Abstract

Spontaneous mutants of moth bean. Rhizobium (Bradyrhizobium sp.) MR 67, resistant to streptomycin, kanamycin, neomycin and ampicilin were isolated at the graded levels of antibiotics. The mutation frequency was 2.54 x10^-8, 2.66 x10^-8and 3.54 x10^-8 with streptomycin, neomycin and kanamycin, respectivlely. Strain MR 67 was completely resistant to ampicilin. All the twenty mutants' isolated and tested for each antibiotic, were stable in their resistance and sensitive to lysis by lytic phage MRV 67. Studies on the performance of the mutants with moth b~an variety "Jwala", under controlled conditions revealed, that the strains were symbiotically effective. The mutants produced lesser nodules, but their symbiotic efficiency was comparable with the parents. Mutants superior in effectiveness were frequently associated with kanamycin resistance than streptomycin or neomycin resistance.