Rhizobium Tropici vs. Rhizobium Etli: A comparative analysis of nitrogen fixation in common bean under water stress

Abstract

Drought stress is one of the most important factors limiting plant growth; in particular, water is
regarded as a major problem in symbiotic nitrogen fixation for legume growth. The adverse effects of
water stress on the rhizobial symbiosis of common bean genotypes CocoT and Flamingo were
investigated in field conditions. Common bean plants were inoculated with rhizobia strains: Rhizobium
tropici CIAT899 or Rhizobium etli 12a3, and grown under field conditions, plants were spray irrigated
until the first flower was observed on set. Irrigation was stopped for 20 days in plants submitted to
water stress. The enzyme-linked immunosorbent assay (ELISA) technique was used with polyclonal
antibody to assess the occupancy in nodule of the rhizobia used for inoculation. Under water stress, a
significant decrease in nodule population, nodules biomass, shoot content of nitrogen, growth and
chlorophyll with all symbioses, whereas proline accumulation increased. The interaction between
symbiosis and water stress for all parameters was significant. Overall, 12a3 was more efficient than
CIAT899 for Flamingo, though not for CocoT. It is concluded that symbiosis between Flamingo and
12a3 has potential for application in field under water stress in desert soil.