Growth Performance and Nitrogen Fixing Efficiency of Faba Bean (Vicia faba L.) Genotypes in Symbiosis with Rhizobia under Combined Salinity and Hypoxia Stresses

The present study was carried out in order to investigate the behaviour of six faba bean (Vicia faba Minor) genotypes (Saber 02, Locale, Baachar, Badii, Chourouk and Najeh) in response to salinity and flooding (hypoxia), either alone or combined, to identify tolerant genotypes and to select efficient faba bean-rhizobia symbiosis under salinity and/or hypoxia conditions. faba bean genotypes were cultivated in three agricultural soils with either low (160 p.s/ cm) or moderate (1850 ps/cm) salt content and submitted or not to a 30-day long flooding period. Growth parameters and photosynthetic performance were analyzed at the end of the flowering period. At harvest time, the Najeh genotype showed the highest dry mass production in both control and hypoxia conditions (7.90 and 6.75 g /plant, respectively), whereas Saber 02 showed the lowest (3.75 and 2.25 g/plant, respectively). Differences between genotypes were less marked in salinity or combined salinity/flooding conditions. Principal component analysis of the analyzed parameters revealed that the Najeh genotype presents the best growth and the lowest photosynthetic perturbation and lipid peroxidation levels, whether under control or hypoxic conditions, whereas Saber 02 and Locale genotypes were less productive. Ninety bacteria strains were isolated from Vicia faba root nodules. Of these, 47 strains were identified as rhizobia, and 20 were able to re-nodulate the host plant. After the characterization, identification and selection process, four strains were selected as the best faba bean symbiotic partners based on their symbiotic efficiency and salt tolerance behaviours. Our results suggest that faba bean tolerant genotypes in symbiosis with these strains could be useful in enhancing legume cultivation under saline and hypoxia field conditions.

Automated summary

This study investigates the behavior of six faba bean genotypes in response to salinity and flooding, and selects efficient symbiosis partners under these conditions. The results show that the Najeh genotype exhibits the best growth and lowest photosynthetic perturbation levels, while Saber 02 and Locale genotypes are less productive. Four strains of rhizobia are selected as the best symbiotic partners based on their efficiency and salt tolerance behaviors.