Effect of drought stress on chlorophyll fluorescence, antioxidant enzyme activities and gene expression patterns in faba bean (Vicia faba L.)

Drought is a major environmental stress that limits faba bean growth, leading to considerable reduction in their productivity. Two genotypes (Giza 3 and Hara) were evaluated under three water treatments (90%, 60% and 30% field capacity). The results showed that water stress affects negatively chlorophyll fluorescence parameters at different levels of water deficit and the variations of Fv/Fm, phi PSII and electron transport rate in Giza 3 were largely higher than those in Hara. Drought preferentially enhanced the activities of superoxide dismutase, catalase and guaiacol peroxidase whereas it did not affect ascorbate peroxidase activity. Real-time reverse transcriptase-polymerase chain reaction results demonstrated that the expression of aquaporin (PIP), myeloblastosis (MYB), nine-cis-epoxycarotenoid dioxygenase, late embryogenesis abundant, dehydrins (Dhn), heat shock protein (HSP) and APETALA2/ethylene-responsive factor was modified in response to drought conditions and that all genes were differentially expressed in Hara and Giza 3. The observed expression patterns of these genes might be due to water deficit intensity according to cultivars tolerance to drought. Hara with the highest level of antioxidant enzyme activities, the accumulation of proline content and the expression level of Dhn, HSP and MYB gene throughout all conditions tested is reported more drought tolerant than Giza 3. This study should contribute to explaining the physiological, biochemical and molecular mechanism tolerance drought stress and improving breeding program in faba bean.