Effect of osmotic stress on the dehydration tolerance and cryopreservationof Solanum tuberosum shoot tips.

Four different preculture treatments were tested for their ability to enhan ce survival of potato shoot tips (cv. Desiree) after both dehydration and c ryopreservation. The encapsulation/dehydration method and rapid freezing we re used. Further, accumulation of sucrose, glucose, fructose, glycerol and proline in the apices during the treatments was measured. Very high interna l sucrose concentration (up to 27.8% of dry mass) was essential to reach hi gh survival rates after cryopreservation, but not after dehydration only. T he highest survival rate (78.8%) was obtained when osmotic stress was induc ed by adding of 2 M sucrose solution to donor plants for 5 days, followed b y 0.7 M sucrose preculture of isolated shoot tips for 1 day. The results de monstrate that drought-hardening would be able to replace the effect of low temperatures in such plants, which are not able to be cold-hardened.