Study the Possibility of Using the Electrolyte Leakage Index for Evaluation of Cold Tolerance in Sugar Beet (Beta vulgaris L.) Cultivars

In order to evaluate the electrolyte leakage as an indicator for cold injury in eight sugar beet (Beta vulgaris L.) cultivars including Rasoul, Shirin, IC, 7233 (national cultivars), Afshari, Paolina, Rhizofort and Laetitia (foreign cultivars), a trial carried out at Crop Physiology Lab. of Agriculture College of Ferdowsi University of Mashhad in 2006. In this study beet cultivars, with 8 freezing temperatures (0, -2, -4, -6, -8, -10, -12 and -16 °C) as a complete randomized design in a factorial arrangement with three replications. Plants were kept until 4-5 leaf stage in natural environment, then transferred to the thermogradient freezer. The cell membrane stability of beet cultivars was measured through electrolyte leakage and the lethal temperature 50 (LT50) of leaf samples based on electrolyte leakage percent also were determined. Results showed that there were significant differences (p≤0.01) among freezing temperatures and cultivars for electrolyte leakage and LT50. As temperature decreased below -4 °C, electrolyte leakage of all genotypes were increased. Among beet cultivars, IC cultivar had the highest, and 7233 cultivar had the lowest cold tolerance according to the LT50. Also in grouping sugar beet as local and foreign cultivars, there were no significant different in electrolyte leakage among cultivars. According to the high correlation between electrolyte leakage percent and LT50 (r= -0.81), it seems that using this index for evaluation of freezing tolerance injury in sugar beet could be useful.