Development of Alfalfa Tolerant to Salinity Stress Using Organogenesis Technique

The possibility of using Organogenesis culture to evaluate salt tolerance of cultivated alfalfa plants (Medicago sativum L.) was studied and related to the response obtained by callus culture. The research was carried out in the tissue Culture Lab, Department of Aridland Agriculture, College of Food Systems, UAE University during seasons 2000/2001 including two Lab Experiments: 1) Callus Initiation and shoot formation and 2) Evaluation of in vitro callus and plantlets under salinity stress. Seeds of alfalfa were sown in pots, then leaves of the seedlings were separated to blades and petioles and placed in jars containing 50 ml of the modified MS medium. For callus induction and shoot formation, modified Murshig and Skoog and B5 were used in addition to two growth regulators being 2,4-D and BA In order to evaluate the salt response of the in vitro callus and plantlets, the induced calli and formed shoots in Experiment I were taken and placed on modified Murshig and Skoog mineral salts and B5. Sodium Chloride (NaCl) at four doses (0, 3000, 6000 and 9000 ppm) were used in jars. The results of this study indicates that the best concentration of 2.4-D and BA to obtain higher number and weight of callus and also higher values of shoot weights can be obtained from the concentration of 2 mg L-1 in both cases. Increasing of NaCl salt concentration in the media causes significant reduction in the seedling weight but positively correlated with Na and negatively correlated with K concentration in the seedling tissues. NaCl salt concentration of 6000 ppm was high enough to induce harmful effect on the seedling fresh weight, whereas number of generated shoots formed roots was dramatically affected by increasing NaCl concentration up to 3000 ppm and there was no shoots formed roots established afterwards. The results obtained in this study suggest that Organogenesis technique may be useful for rapid evaluation and screening of alfalfa segregant populations in a breeding program using the rooting and shooting parameters.