Callus Growth and Ion Composition in Response to Long-Term NaCl-induced Stress in Two Sugarcane (saccharum Sp.) Cultivars

In this work, the effect of different concentrations of NaCl on calli induced from two sugarcane cultivars NCo310 and CP59-73 was studied. Growth and ion concentrations (Na+, Cl-, K+ and Ca2+) of calli were determined after 1, 2 and 3 months of stress with the objective to understand the cellular mechanisms operating in salt stress tolerance and to determine the implication of inorganic fraction in salt tolerance in sugarcane cultivars. A negative effect of the NaCl concentration and the duration of stress exposure on the callus rate growth was observed in both cultivars and with more extent in CP59-73 cv. Results showed an increase in Na+ and Cl– and a decrease in K+ and Ca2+ concentrations after 1, 2 and 3 months of salt stress exposure. It also showed that resistant cv. NCo310 stressed calli accumulated less Na+ and retained more K+ and Ca2+ than CP59-73 calli. Cl- appeared to be involved in osmotic adjustment since the resistant cv. NCo310 stressed calli accumulated more Cl- than CP59-73 ones. These results suggested that the resistance to salinity in sugarcane is associated with a high K+, Ca2+ and Cl- concentrations and a low Na+ concentration within cells. Key words:  sugarcane (Saccharum sp.), salt stress, ion uptake, callus growth, long-term stress exposure.