A new concept about carbon source roles on in vitro microtuberization of potato (Solanum tuberosum L.)

The present investigation was conducted to understand carbon source roles on rapid in vitro microtuber production of potato. The single-node explants from in vitro plantlets were cultured into microtuberization medium including MS basal medium supplemented with different concentrations (0.0, 0.05, 0.11, 0.17 and 0.23 mol.l-1) of sorbitol (nutrient or osmotic effect), sucrose or PEG (osmotic effect). After 5 weeks of incubation (at 18±2oC in dark condition), the microtuber initiation and formation percentage, microtubers fresh weight, length and diameter as well as eye number on microtuber were evaluated. The results showed that microtuberization traits were significantly influenced by carbon sources and their concentrations. Comparison showed that the sucrose was more suitable and effective for microtuberization than PEG and sorbitol. Microtuberization decreased when nodal explants were cultured on medium containing different sorbitol concentrations. The PEG treatments conducted to a decrease of microtuber production process. Also it is a well established fact that usage of PEG in microtuberization media had osmotic role. Our research showed that sorbitol treatments, on all microtuber traits had only osmotic role. We suggest that microtuberization is related to the nutrient/osmotic pressure ratio, where increasing of nutrient source by high concentrations of sucrose reduce the negative effect of osmotic pressure.