Rhizobia Strain and Legume Genome Interaction Effects on Nitrogen Fixation and Yield of Grain Legume: A Review

Abstract

Though molecular nitrogen represents nearly 80% of the earth’s atmosphere, it is chemically inert and cannot be directly assimilated by plants. Only limited numbers of prokaryotes are able to convert the N 2 molecule into a usable form of N through a process known as biological nitrogen fixation. Rhizobia are soil bacteria able to form nodules and establish symbiosis with the roots or the stems of leguminous plants. Nitrogen fixation in legume provides important economic advantages for crop production by reducing the cost of N fertilizer. This review covers contribution of biological nitrogen fixation in agriculture, rhizobia and host-legume related factors influencing symbiotic performance. It highlights the rhizobial strain and host-legume interaction effects on N 2 fixation, soil residual nitrogen, and nitrogen and phosphorus uptake of the plant. The review aims to elucidate the approach for selection of the best rhizobia strain-legume variety combination for maximum nitrogen fixation and yield of grain legume. Variation in nodulation and nitrogen fixation frequently occur in a bacteria strain-legume cultivar specific manner. Genotype of both the host and the competing rhizobia strains have been shown to influence inoculant performance .