EFFECT OF VARIOUS PRECULTURE AND OSMOTIC DEHYDRATION CONDITIONS ON CRYOPRESERVATION EFFICIENCY AND MORPHOGENETIC RESPONSE OF CHRYSANTHEMUM SHOOT TIPS

The aim of this study was to evaluate the influence of sucrose concentration in the preculture medium, as well as the duration of osmotic dehydration on the efficiency of chrysanthemum 'Richmond', 'Lady Orange' and 'Lady Salmon' cryopreservation by encapsulation-dehydration technique. For all cultivars tested, the best regrowth of cryopreserved shot tips was recorded with 0.25 M sucrose concentration and 10 mu M ABA during a two-week preculture, followed by a 4-or 7-day osmotic dehydration. The survival rate ranged from 56.8-58.0% (the Lady group) to 63.6% ('Richmond'). However, the ability to grow was smaller and reached 18.2-50.7%. It was found that higher sucrose concentration during the preculture slowed the growth of chrysanthemum shoot tips and led to an increased formation of multiple shoots (by activating axillary buds) or deformed adventitious shoots (incapable of further growth). The frequency of tissue hyperhydricity also increased, while the rhizogenesis efficiency decreased when higher sucrose concentration in the preculture medium was applied. The influence of osmotic dehydration duration on the explants morphogenetic response was cultivar-dependent.