Evaluation of the Quantitative Characteristics of Sugar Beet O-Type Lines under Drought Stress

One objective of drought resistance breeding of sugar beet is to introduce cultivars with lower yield loss under drought stress. In this study, 29 sugar beet O-type lines together with a tolerant foreign cultivar as control (IR7); a susceptible genotype (191); genotypes 30908, 31290, 31291, and 31292; and forage beet bulk 7221 were evaluated in a split-plot experiment on the basis of a Randomized Complete Block Design (RCBD) with three replications in Motahari Research Station in 2012. The main plot was devoted to stress (at two levels of normal irrigation and stress application) and the sub-plots were devoted to 36 lines and cultivars under study. Under both conditions, the plots were normally irrigated until thinning and plant establishment and then, they were irrigated on the basis of about 80-90 and 270 mm evaporation from evaporation pan under normal and stress conditions, respectively. The results indicated that mean root, raw sugar, and white sugar yield decreased by 59, 72, 76% respectively in response to drought stress. The significance of the effect of genotype and the interaction between stress and genotype on crop quantitative traits show the wide diversity of genetic materials in terms of the response to drought stress. Under drought stress, O-type lines 2, 3, 5, 7, 10, 13, 16 and 26 had significantly higher root yield. However, no significant difference was observed among genotypes in terms of raw and white sugar yield. In conclusion, the development of sugar beet lines tolerant to drought appears to be promising.