Comparative Responses of Helianthus annuus Plants and Calli Exposed to NaCI: II. Selection of Stable Salt tolerant Calli Cell Lines and Evaluation of Osmotic Adjustment and Morphogenic Capacity

Salt tolerant cell lines of Helianthus annuus L. cv. SH222 were selected by sub-culturing cotyledon-derived calli on MSmod medium containing 0, 50, 100, 200 and 300 mmol/L NaCl. NaCl-adapted calli were compact and developed a dark green colour but sustained a regular growth on salt media. Calli adapted to 200 mmol/L (HA2) and to 300 mmol/L NaCI (HA3) had maximum growth rates at, respectively, 50 and 100 mmol/L NaCI; Na, Cl- and B contents increased in HA2 and HA3 calli, whereas K, Ca, NC3-, HPO42-, Co, Fe and Mo levels decreased. There was an increase in glucose, fructose and sucrose levels in NaCl-adapted calli. Also, the contents of free amino acids increased significantly in adapted calli. This increase was mainly due to Pro followed by Ser and Gly. The presence of 50 mmol/L NaCl increased the rate of shoot formation, while higher concentrations inhibited it. Rooting was completely inhibited even at low concentrations of NaCI. Leaves from tolerant shoots (HA2-2 and HA2-5 lines) were transferred to MSmod medium to induce calli in the absence of NaCl. Calli from HA2-5 line sustained growth after transference to 200 mmol/L NaCl, indicating the persistence of salt tolerance at the mitotic level. It was possible to regenerate plants from HA2-5 shoots but plants were stunted and did not survive to acclimation.