Effect of drought stress on the quality of sugar beet.

Quality of sugar beet is a combination of physical and chemical properties of beets which effect on product process. Water stress is one of the main factors affecting the quality properties of sugar beet. is water stress. The objective of this experiment was to study the effect of water stress on the quality and quantity of sugar beet. The present research was conducted in Motahary Station, Karaj in two years, 2005 and 2006. The experiment was based on split plot design, in which eight irrigation regimes (non-stress, in this situation irrigation is applied always in the growth season after 80 mm evaporation from pan evaporation, three levels of irrigation cut in early growth stage, after plant establishment, irrigation after 130 and 180 mm evaporation from evaporation pan and after about 45 days, two levels of continuous drought stress, in these situations irrigation were applied in the growth season after about 130 and 180 mm evaporation from pan evaporation, two levels of late season drought stress, irrigation was cut when estimated that evaporation from pan have been about 130 and 180 mm till the end of growth season) were allocated to the main plots. Three sugar beet genotypes, 191, BPmashhad and BPkaraj, were arranged in the sub-plots. The results showed that water content of storage roots were not affected by drought stress treatments (P 0.05). Sugar Content (SC) was influenced by beet water content. Determining coefficient showed about 58 and 55 percent changing in SC and WSC in roots depends on water content of root. Therefore, it may recommend that SC base on dry weight of root in order to study effects of irrigation management on these properties.-Effects of different levels of irrigation management on SC base on dry weight of root were not significance. Irrigation has not significant effects on extraction coefficient of sugar. Sever early drought stress, irrigation after about 45 days, reduced sodium quantity in compare to non stress and other irrigation levels. Nitrogen content was increased significantly by both levels of drought continues in compare to other irrigation levels. Potassium content was not significantly affected by irrigation. –Generally, drought stress decreased alkalinity and increased marc percentage. Minimum alkalinity and maximum marc percent were observed in two levels of continuous drought. In this research, the effect of irrigation was not significant for reducing sugar, resistance and elasticity of beet (P 0.05). Totally, stress decreased root yield. Least root yield was observed in two levels of continues drought stress, 25.01 and 25.78 t.ha-1, respectively. Root yield in severe drought stresses in the early (42.27 t.ha-1) and late (34.65 t.ha-1) season were significantly lower than root yield in compare to non stress conditions (46.68 t.ha-1, P 0.05). Although, other stresses had less root yield in compare to non stress but the differences were not significant (P 0.05). White sugar yield was decreased in two levels of continuous drought stress in compare to non stress conditions. This important property was not affected significantly by other levels of irrigation treatment. Genotype of 191 has the most SC in dry weight of root and Extraction coefficient of sugar in compare two other genotypes. Also, sodium content and alkalinity of genotype 191 were lower than two other genotypes. Alkalinity of BPkaraj was more than BPkaraj. F test did not show significant interaction between genotypes and irrigation for all traits.