Response of potato’s cultivars and promising clones to osmotic and temperature stress under in vitro conditions

In order to study responses of potato plantlets under in vitro conditions to osmotic and temperature stresses, a factorial experiment was conducted in a completely randomized blocks design with three replications. The first factor was osmotic stress caused by polyethylene glycol 6000 in four levels including control, 0.5, 0.1 and -1.5 MPa which were equal to 0, 200, 300 and 370 grl-1 PEG. The second factor was temperature at three levels of 15, 25 and 35 °C applied on plantlets of three Promising clones (143, 301 and 306) and two commercial cultivars (Picasso and Marfona) in MS medium. Physiological and biochemical traits including relative water content (RWC), electrolyte leakage (EL), proline, catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) as well as protein content were measured. Results of variance analysis showed that the simple effects of three factors as well as the interaction were significant at 1≤0.01 on the mentioned traits, but the protein content was not significant. Comparing the mean of treatments showed that by increasing the temperature and concentrations of PEG, RWC was reduced, while EL, proline content, CAT, POX and APX enzymes activity were increased. Also, results indicated that Marfona was more tolerant to stress conditions than other varieties and clones, which seems is due to preventing the effects of stress by increasing the accumulation of proline and the activity of antioxidant enzymes. Clone 306 was more susceptible than other varieties and clones and showed more vulnerability to stress and its plantlets were killed by increasing stress levels. The combination of osmotic and temperature stresses were not tolerated by potato’s plantlets under in vitro conditions, because osmotic stress of -0.5 MPa and higher in combined with 35°C caused the plantlets to dry.