In vitro expression of sodium chloride tolerance of some solanum species

Fifteen solanum species (13 wild potato forms and two cultivars, Desiree and Hansa), representing different degrees of sodium chloride (NaCl) tolerance, were chosen to study the in vitro expression of NaCl. Two-node explants from in vitro propagated (on a medium of murashige and skoog (MS) -salts) plantlets were placed in honey jars containing 50 ml MS supplemented with 0.1mg/1 indole acetic acid (IAA), 0.2 mg/1 benzylaminopurine (BAP) and either one of four NaCl concentrations (0,40,80 and 120 mM/1). They were placed in a culture room at a temperature of 20C-23C, 4000 lux light intensity and 16 hours light period, and arranged in a complete randomized design with four replicates. The results showed that shoot growth in all species was inhibited by increasing NaCl concentration. Analysis of explant shoots and roots showed that Na''+ and Cl''- concentrations increased with increasing NaCl cocentration, whereas those of K''+ and Ca''2''+ decreased. There was a tendency of lower Na''+ and Cl- concentrations in the shoots and higher concentrations in the roots of the NaCl tolerant compared to sensitive species. K''+ concentrations in the shoots and Ca''2''+ concentrations in the roots were higher in NaCl tolerant species than in sensitive ones. Na''+ and Cl''- concentrations in the shoots and explant main stem length were negatively correlated (r=- 0.91 for both). The correlation coefficients between the main stem length and K''+ concentration in shoots and Ca''2''+ concentrations in the roots were positive and highly significant (r = 0.74 and r = 0.90, respectively). However, Na''+ and Cl''- concentrations in the root were not correlated with shoot length. shoot length could be a good trait for a quick screening of potato genotypes for NaCl tolerance using two-node cuttings in vitro. However, this approach will be of practical value if a close relationship is proved to exist between the in vitro and in vitro response of plants growing under salt stress.(Author)