THE ROLE OF RHIZOBIAL BIODIVERSITY IN LEGUME CROP PRODUCTIVITY IN THE WEST ASIAN HIGHLANDS .1. RATIONALE, METHODS AND OVERVIEW

The numbers of bacteria and the nitrogen fixing efficiency of isolates of Rhizobium leguminosarum, R. ciceri and R. meliloti with appropriate legume crop species were determined from soils collected from a wide range of locations in Turkey with elevations between 500 and 2200 m. For vetch and lentil nodulated by R. leguminosarum, many native rhizobia are present in most locations but they often have limited nitrogen fixation capacity. However, for chickpea nodulated by R. ciceri, relatively small numbers of bacteria and the almost universal ineffectiveness of fixation capacity point to a need for artificial seed inoculation of chickpea crops as a future agronomic priority. The wide range of bacterial numbers, considerable geographic inconsistency and generally low effectiveness of the indigenous rhizobia associated with the annual Medicago spp. suggest that inoculation would initially be a sensible precaution for all sowings.