COMPARATIVE NACL TOLERANCE OF LUCERNE PLANTS REGENERATED FROM SALT-SELECTED SUSPENSION-CULTURES

Batch suspension cultures of Lucerne (Medicago media cv. Rambler), ini tiated directly from surface-sterilized leaflet explants, were used to produce cell lines tolerant to 200, 250 and 300 mol/m(3) NaCl by succ essive subculture into media of progressively higher salinity. Plants regenerated from these cell lines were significantly more salt toleran t than the original, unselected Rambler plants, another cultivar of M. media and 4 cultivars of M. sativa. The salt-tolerant plants showed e nhanced Na+ and Cl- exclusion when compared with the unselected cultiv ars. Comparisons of the salt-tolerant, 250 mol/m(3) NaCl-selected with original unselected Rambler plants showed the salt-tolerant plants we re able to maintain lower Na+/K+ ratios than the unselected plants. Ca 2+ gave some amelioration of NaCl toxicity but the salt-tolerant plant s did not differ from the susceptible plants in this respect. A multip le regression equation has been computed accounting for 90% of the obs erved variation, that relates the growth of the plants to Na+/K+ ratio s and Cl- concentrations of roots and shoots and their interactions.