Effect of Osmotic Pressure on In vitro Microtuberization of Potato cv. Agria in Different Concentrations of Sucrose and PEG

In order to evaluate the effects of five concentrations of sucrose and PEG (0.0, 0.05, 0.11,0.17 and 0.23 mol.l-1) on microtubers initiation, formation and growth, a factorial experiment based on completely randomized design with five replications was carried out. Nodes fromin vitro potato shoots were cultured for microtuberization in MS medium and incubated in constant darkness in growth room at 20 ±1oC. Analysis of variance revealed significant differences among treatments for initiation and formation of microtubers, as well as microtuber length, diameter and fresh weight. Sucrose was more effective than PEG on microtuberization process (all traits).Thus; it was show that application of high levels of sucrose was very useful in microtuberization. Increasing of sucrose concentrations efficiently improved in vitro microtubers number without negative side effects on fresh weight and size. PEG led to a decrease in microtuberization (all traits). High concentrations of PEG restricted microtuberization due to reduce water and nutrients uptake by node explants from medium. On the other hand the use of high concentrations of osmotic material was significantly effective on microtubers dormancy which is useful in germplasm exchange. Results of study like the one presented here, could be very useful in better understanding of physiological mechanisms involved in microtuberization process and useful in approaching breeding objectives as well.