Effect of freezing stress on some of sugar beet (Beta vulgaris L.) genotypes electrolyte leakage

In general, spring cultivation of sugar beet is Prevalent, but nowadays because of water sources limitation and also plants low water use efficiency in this time of cultivation, autumn cultivation is growing up. Several assessments also have showed that in compare with spring cultivation, autumn cultivation of sugar beet has other benefits including reducing the likelihood of plant disease and pests outbreaks as well as high radiation use efficiency and also other resources use efficiency. In contrast,in autumn cultivation several vital processes will be disturbed when sugar beet plantsare exposed to chilling stress condition. Thus, it’s necessary to identify chilling tolerance of sugar beet genotypes for this purpose, but because of temporal and spatial variation in chilling stress occurrences in natural environmental condition, it might be lead to uncertain results. As well as, selection processes of sugar beet chilling tolerance genotypes in the natural conditions will take long time and more cost than controlled conditions. In order to evaluation ofchilling tolerance in number of sugar beet (Beta vulgaris L.) genotypes (Jolge,Palma,Giada, Monatunno, SBSI1, Super Ma and PP8) that were candidate for autumn cultivation, an experiment was performed in 2009 in the Faculty of Agriculture Ferdowsi University of Mashhad as a factorial experiment in completely randomized design with three replications. In this study, sugar beet genotypes were exposed to 10 freezing temperatures (including 0, -2, -4, -6, -8, -10, -12, -14, -16 and -18 °C) at controlled conditions and then amount of electrolyte leakage was measured. Results showed that the effects of freezing temperature and genotype on electrolyte leakage were significant. Jolge, PP8 and Super Ma genotypes with 38.7 %, 38.5 % and 37.7 % had the highest amount of electrolyte leakage, respectively and the Monatunno genotype with 26 % had the lowest amount.Interaction effect of genotype and temperature on LT50el was significant, statistically.Monatunnogenotype with -11.1 and Palma genotype with -9.6 degree centigrade had the highest and the lowest freezing tolerance, respectively. Based on correlation between electrolyte leakage and LT50el, sugar beet genotypes separated in to two groups. Sensitive group including Jolge, PP8, Sbsi1 and Superma genotypes and resistant group including Monatunna, Giada and Palma genotypes. There was high significant correlation (r=0.98***) between electrolyte leakage and LT50el into resistant group while it was low (r=0.64) into the sensitive group.Chilling stress is one of the major limiting factors for sugar beet cultivation in regions that have moderate weather. Therefore, identify and select the genotypes that are able to resist under this conditions is the first preference. As well as, based on exist of high correlation between electrolyte leakage, LT50el and plants resistance to chilling stress in several experiments it seems that we are able to use this trait to assessment of high tolerant genotypes candidate for autumn cultivation in the Iran.