Genetic Variation for the Tolerance To NaCl Stress in Relation To Cultivars: Rooted Vs Non-Rooted In Vitro Studies

Abstract

Micro-propagated plantlets were used to screen potatoes for salinity (NaCl) tolerance. Nodal cuttings were placed in media with NaCl. The ability of cuttings to induce roots, in part, determined the tolerance of a given clone. We compared the response of rooted versus non-rooted nodal cuttings to salinity stress. Rooted or non-rooted nodal cuttings of "Russet Burbank", "Dark Red Norland", "Snowden", "Atlantic", and "Superior" potato plants were propagated in vitro on a medium containing 60 mM NaCl with 3 mM CaCl2. Rooted cuttings were produced by growing cuttings in normal MS medium and MS medium + 60 mM NaCl for 11 days. These rooted cuttings were then transferred to media containing salinity treatments. Thirty replicates were used per treatment. Observations were made up to 32 days after transfer. Results show: (i) Rooted cuttings displayed more tolerance to normal MS medium + 60 mM NaCl stress than non-rooted cuttings; (ii) Injury by NaCl does not appear to be due to osmotic stress. The primary cause of injury is likely ionic toxicity rather than osmotic stress, as evidenced by the protective effect of added CaCl2, which mitigates the toxic effects of Na+ ions, and the observed symptoms of necrosis and chlorosis. We suggest that rooted cuttings better simulate the response to saline water irrigation.