Competitiveness of introduced Rhizobium strains for nodulation in fodder legumes

Abstract

Rhizobial strains were isolated from the root nodules of Medicago sativa (alfalfa) and Trifolium subterraneum (clover) plants. These strains were tested for their growth rate, morphological characteristics and utilization of different carbon sources. Four out of six strains isolated from the alfalfa plants re-nodulated the host plant confirming them as the strains of Rhizobium meliloti. Similarly five out of eight strains isolated from clover plants caused infection on clover corroborated as Rhizobium leguminosarum bv. trifolii strains. The nitrogen fixing ability of these strains ranged from 266 -673 n moles of C 2 H 4 produced h -1 g -1 nodule dry weight. The competitive ability of inoculated strains with indigenous population was studied with two local soils selected on the basis of their cropping history in a pot experiment. The isolated strains MS4 and TS1 were found to be most effective and competitive for alfalfa and clover respectively. Overall recovery of the inoculated strains was 30% for alfalfa and 100% for clover as determined by fluorescent antibody technique. MS4 and TS1 are potent strains for the production of biofertilizer for fodder legumes.