The Role of Rhizobial Biodiversity in Legume Crop Productivity in the West Asian Highlands. III. Rhizobium meliloti

Abstract

The native rhizobia capable of symbiosis with potential pasture legume crops for the west Asian highlands were surveyed and estimates made of the numbers and nitrogen fixing efficiency of isolates of Rhizobium meliloti with a range of annual Medicago species. Soils were collected from 105 sites at elevations between 500 and 2200 m. Numbers of bacteria were generally adequate to permit efficient nodulation but the nitrogen fixing efficiency of three of the four host species with the indigenous rhizobia was often low. In contrast, nitrogen fixation in M. aculeata was generally highly efficient. No overall geographic pattern in either numbers or efficiency of nitrogen fixation was evident. Substantial further research is required before annual medic crops can be successfully introduced into highland crop/livestock systems in Turkey and elsewhere in the west Asian highlands.