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

Abstract

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 µs/cm) or moderate (1850 µs/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.

Recent progress and potential future directions to enhance biological nitrogen fixation in faba bean (Vicia faba L.)

“…This suggests that there is potential to select for these traits in breeding programs. For example, a faba bean genotype with tolerance to salt in Mediterranean‐type climates has been identified from pot studies (Benmoussa et al., 2022 ), although it is not clear whether the increased tolerance is a result of increased BNF. Selecting for further genotypes with increased tolerance to particular stresses and subsequently assessing their performance for BNF and yield under field conditions in future studies are a potential route to enhancing these traits in faba beans (Figure 3 ).…”

Plant–Environment Response Pathway Regulation Uncovered by Investigating Non-Typical Legume Symbiosis and Nodulation

“…This has also been shown to be the case with Vicia faba (faba bean), where rhizobia strains with different levels of salt tolerance could lead to increased salinity tolerance for the host. Rhizobia with higher salt tolerance themselves had on average higher N 2 fixing capacity (32.28 ± 1.47 µmol h −1 Plant −1 ) compared to rhizobia with a lower salt tolerance (13.83 ± 1.65 µmol h −1 Plant −1 ), and testing these under salt conditions may help V. faba survive these conditions [ 94 ]. Salt-tolerant rhizobia have also been shown to directly improve the salt tolerance of plants by changing amino acid composition towards the accumulation of amino acids with protective functions in the nodules, such as proline, which is involved in osmoregulation [ 95 , 96 ].…”