Rhizobia: Culture Collections, Identification, and Methods of Preservation

Abstract

Across the globe nitrogen is limiting primary productivity. Although fertilizer nitrogen could supplement soil nitrogen depletion, efforts should be to augment soil biological nitrogen fixation mediated by microbes. This could be addressed by conservation and sustainable use of rhizobia that can fix nitrogen in soil in association with legumes. Rhizobia commonly occur in soils but often fail to produce effective nodulation either because their population in soil is low or those present cannot effectively nodulate the particular legume. Rhizobia present in various ecosystems are considerably diverse; at present 130 species within 15 genera are reported. Rhizobial inoculation is almost always needed when certain new leguminous crops are introduced to new areas or when ineffective and incompatible rhizobia are present in the soils. For this, depository of authentic microbial gene pool is a must. Culture collection centers act as repository of valuable microbial strains. In the changing global scenario, these centers are becoming Biological Resource Centres (BRCs), carry out research, enhance value of strains, and control access to dangerous microorganisms. For adoption and popularizing use of rhizobium-legume technology, their isolation, identification, preservation, and deposition in biological banks are imminent. Moreover, there is a need to identify the compatible rhizobium- legume symbioses for sustainable agriculture. 6.1