utilization of mannitol as drought stress agent in sugar beet seed germination and early growth stages in vitro

seeds of nine sugar beet lines: five drought tolerant, two susceptible, and two medium tolerant were washed, sterilised, dried, and sown in water agar medium for germination test. seedling growth characters such as cotyledon fresh weight (cfw), cotyledon dry weight (cdw), root fresh weight (rfw), root dry weight (rdw), and root length (rl) were determined after the end of 28 days period of experiment. mannitol was used as osmotic stress inducing substance at 0.0, 0.2, and 0.3m concentrations using a factorial design with three replications and 20 seeds per treatment. relative germination percentage was determined as the germination ratio in the two stresses levels to that of the control (0.0 m mannitol). similarly, relative growth of rl, rfw, and cfw were also determined for sugar beet seedlings. significant differences were found between stress levels for all seedling characters. great genetic variation was found among genotypes for the germination rate and seedling characters except for cdw and rdw. under nonstress condition, relative germination % and relative growth % for tolerant genotypes were greater than those of susceptible genotypes at early growth stage of seedlings. results showed that drought tolerance could be expressed even in the seedling stages of sugar beet plant and may be considered as a criterion for early screening of potentially drought tolerant genotypes.