Importance of explant size and origin and of preconditioning treatments for cryopreservation of garlic shoot apices by vitrification.

This paper investigates the effect of the origin and size of the explants employed and of the preconditioning (cold acclimation, preculture) and loading treatments on survival and regeneration of cryopreserved garlic shoot apices using vitrification with the PVS3 vitrification solution. Both the origin and size of explants had a significant effect on regeneration of cryopreserved apices. Higher regeneration was generally observed with apices excised from bulbs and bulbils, followed by cloves, and those originated from larger propagules regrew more rapidly. Smaller apices (1.5 or 3.0 mm in diameter) displayed higher regeneration than large ones (4.5 mm in diameter). Cold acclimation at 5 degree C of apices before freezing had no positive effect on regeneration after cryopreservation. Preculture of apices at 10 or 23 degree C for more than 3 days had a detrimental effect on regeneration. The optimal sucrose concentration in the preculture medium was 0.3-0.5 M. Loading apices for 30 or 60 min at 23 degree C in medium containing 2 M glycerol + 0.4 M sucrose or 1 M glycerol + 0.8 M sucrose had no effect on regeneration after cryopreservation, in comparison with apices cryopreserved without loading treatment. Under optimal conditions, regeneration of cryopreserved apices sampled from large cloves was above 90 percent.