Abstract
Seeds of fourteen tomato (Lycopersicon esculentum Mill.) cultivars were germinated under 0, 25, 50, 75, 100 mM NaCl. According to their germination response, six cultivars were selected as follows: salt-tolerant (Pascal and Tnshet Star), moderately salt-tolerant (Imperial and Tnshet Crystal) and salt sensitive (Pahuja and Queen). Explants from hypocotyls of these cultivars were selected for callus induction. About 0.2 g of callus was grown under previous salt levels for four weeks. Callus relative growth rate (RGR), fresh and dry weights, proline, Na+ and K+ contents were evaluated. Significant differences were found among cultivars. Tnshet Star had the highest callus growth, while Pahuja had the lowest under salt levels during the incubation period, high salinity resulted in lowering callus fresh and dry weights as well as reducing callus RGR. In addition, high proline and Na+ content and low K content were obtained. High callus weight correlated with low proline content. Tnshet Crystal had highest callus growth and lowest proline content. Shoot apices were grown in vitro at the same salt levels to evaluate plantlet's growth. Significant differences were reported in vegetative growth traits of tomato plantlets under salt treatments. Tnshet Star had the highest shoot length while Pascal had the highest number of leaves. High salt levels adversely resulted in shortening shoot length, and reducing number of leaves. Shoot and root fresh and dry weights were also reduced.