Abstract

Salinity is one of the major environmental threats to agriculture. In particular, soil salinization is a major limiting factor of symbiotic nitrogen fixation for legume growth. The adverse effects of salinity on the rhizobial symbiosis of common bean genotypes CocoT and Flamingo and the subsequent photosynthesis and plant-growth were investigated in glasshouse. Common bean plants were grown in sterilized sand and irrigated with salt concentrations of 2, 4, 6, 8 and 10 gl-1, respectively and inoculated with rhizobial strains of Rhizobium tropici CIAT899 or Rhizobium etli 12a3. Nodule number and biomass, shoot content of nitrogen and chlorophyll were decreased by increasing salinity with all used symbiosis, whereas, the proline accumulation increased. The interaction between symbioses and salt levels for all parameters was highly significant. Overall, Flamingo inoculated with R. etli had the highest plant growth and nitrogen fixation under salinity. It is concluded that Flamingo has potential for application in field conditions exposed to soil salinization or irrigated with saline water, unless native rhizobial would interact negatively.

Key words: Legume, mediterranean area, rhizobia, salinity.