This study was carried out to determine the tolerance of grass pea genotypes to salinity stress at callus and seedling stages under in vitro conditions. The calli and seedlings of six selected tolerant genotypes based on the primary screening in the field were separately exposed to salinity treatments (0, 125 mM) in vitro. Salinity was imposed with NaCl during in vitro culture, and it significantly affected all seedling traits. Genotype of Iran had the lowest seedling dry weight and therefore was more sensitive to salinity stress. According to salinity tolerance indices for seedlings, genotype Greece-III was characterized as high-yield and relatively high–salt-tolerant genotype. Salinity significantly affected callus size, callus RWC, callus RGR, and callogenesis index. Calli fresh and dry weights were not affected by the treatments. For callus dry weight, genotype Greece-III had the highest mean; and the lowest mean belonged to Greece-I. The stress tolerance indices showed that the highest values belonged to genotype Greece-III, which showed high yield and yield stability and so reasonable salinity tolerance. Cluster analysis divided the genotypes into two separate groups. The first cluster consisted of Iran, Greece-II, and Greece-III genotypes, and the second cluster consisted of Bangladesh, Canada, and Greece-I genotypes. Cluster analysis potentially separated the tolerant and sensitive genotypes to salinity in terms of callus dry weight. Grass pea callus and seedlings were able to survive at 125 mM salinity. Salinity did not affect callus dry and fresh weights, but its effect was remarkable on seedling dry and fresh weights (55% less than control). Therefore, calli were reasonably salinity tolerant. The present study suggests that grass pea was reasonably tolerant to salinity and can survive under salinity conditions during the seedling and callus stages.
