In vitro callogenesis and screening of local varieties of Vicia faba L. to salt tolerance

Faba bean (Vicia faba L.) is one of the most important winter crops for human consumption in the Middle East, where it is facing a significant problem due to the increasing salinity in soil and groundwater. Tissue culture may be used as a useful tool to contribute in the improvement of this plant to tolerate such abiotic stress. This study was undertaken to develop an optimized protocol for in vitro callogenesis and screening to salt tolerance in three faba bean landraces, Iraqi, Halabi and Baraqat, widely cultivated for human consumption in Iraq, Syria and Iran, respectively. Sterilized seeds were sown on MS basal medium deprived of growth regulators. Five types of explants, i.e., epicotyls, stems, shoot tips, leaves and root segments, were excised from the seedlings and used for callus initiation on MS basal medium supplemented with BAP (0.5, 1.0, or 1.5 mg L^‐1). Well established calli were then transferred onto MS medium supplemented with 1 mg L^‐1 BAP and increasing concentrations of NaCl (0, 0.5, 1.0, 1.5, 2.0, 2.5 g L^‐1). Callogenesis rates recorded after six weeks varied between 33 and 100% according to landraces, explants and media. The best results were obtained with shoot tip segments and at 1 and 1.5 mg L^‐1 BAP, in terms of callogenesis rate and callus weight as well. Although unintended in this work, the production of somatic embryos was hopefully possible (33%) during this experiment, occurring within two months after callus initiation, thereby indicating the embryogenic potential of these calli for the three landraces tested. As for the tolerance to salt, the most drastic effect was recorded with 2.5 g L^‐1 NaCl, leaving only 22% of surviving explants for Iraqi and causing the complete loss of calli for Halabi and Baraqat landraces. On the other hand, 2.0 g L^‐1 NaCl allowed 58, 50 and 33% of surviving calli for Iraqi, Halabi and Baraqat, respectively. These surviving calli are currently under proliferation to regenerate somatic embryos that may be tolerant to salt.