Existence and characteristics of rhizobiophages in soybean grown fields in India

Rhizobiophages infective against Bradyrhizobium strains nodulating soybeans were detected in soils of soybean grown fields. Phages infective on two Bradyrhizobium japonicum strains and eight indigenous bradyrhizobia strains were isolated. Distributions of phages in rhizosphere soil were different on indicator strain. The field with soybean after wheat or gram or sorghum contained phages infective on more strains than soybean monocropping fields. Phages were also found in nodule exudates and maximum titre was 4.5x104 particles/g nodule. Host range, lytic activity, plaque characteristics of four phage strains was studied. Competitive ability and symbiotic effectiveness test revealed that ASR011 strain was most compatible and competitive to soybean cv JS335. Phages can be used for an easy test of nodule occupancy by a particular phage susceptible strain at under laboratory and field conditions