Physiological and biochemical responses of two faba bean (Vicia faba L.) varieties grown in vitro to salt stress

Faba bean (Vicia faba L.) is one of the most important legume crops worldwide. High salinity is a major constraint for faba bean productivity in many countries, including Egypt. Here, we examined the effects of salinity-induced toxicity on the growth of two local faba bean genotypes by analyzing physiological and biochemical responses to identify the salt-tolerant attributes between the genotypes. In vitro experiments were carried out to characterize the response of two faba bean genotypes (Sakha 3 and Nubaria 2) to salinity imposed by different sea-salt concentrations (1000, 3000, 5000 and 7000 ppm). For both genotypes, salinity induced a marked reduction in dry matter gain along with a reduction in shoots height, roots length, leaves number and branches number. In addition, the photosynthetic pigments (chlorophyll a, b) were significantly decreased with the increase in salinity. Changes in tissue ion levels, peroxidase (POD) and polyphenol oxidase (PPO) activities depended on genotype, tissue and salinity level. The deteriorating effect of salt stress on the growth performance of genotype Nubaria 2 was lower than that of Sakha 3. This is maybe ascribed to its better antioxidant enzymes activities. Moreover, Nubaria 2 accumulated low quantities of Na+ in the shoots with a higher accumulation of ions in the roots compared to Sakha 3. The obtained results suggested Nubaria 2 seedlings have a strong ability to sustain sea-salt stress by the regulation of transport and distribution of ions and this genotype may be characterized as a salt excluder.