title: Cryopreservation of Salix species using sections from winter vegetative scions.
abstract: Twigs of Salix species are candidates for cryopreservation procedures because they become tolerant of freezing temperatures during mid-winter. We examined several variables in developing a two-step cryopreservation procedure for sections from these twigs. Samples of Salix triandra cooled to -30 or -35 degree C and then transferred to the vapor phase over liquid nitrogen gave the greatest percent shoot formation. Cooling rate to -35 degree C had a major influence on shoot formation. Samples cooled at rates greater than 10 degree C/hour showed no shoot formation. The highest percent of shoot formation was achieved by cooling at 0.21 degree C/hour. Cooling rate from -35 degree C to liquid nitrogen did not influence shoot formation. Warming procedures affected shoot formation. Transferring samples from -160 degree C to either a +2 degree C cold room or to -3 degree C methanol gave similar levels of shoot formation. No shoot formation occurred either with warming in +40 degree C water or very slowly in a Styrofoam box. Eight of eleven Salix taxa tested using the established protocol had significant levels of shoot formation after cryogenic treatment.
authors.affiliation: USDA-ARS National Center for Genetic Resources Preservation, Fort Collins, CO 80521, USA.
authors.forename: Leigh E
authors.initials: LE
authors.lastname: Towill
authors.forename: Mark
authors.initials: M
authors.lastname: Widrlechner
mesh_terms: D015925:Cryopreservation / Q000379:methods*; D018520:Plant Shoots / Q000502:physiology*; D018547:Plant Stems / Q000502:physiology*; D017694:Rewarming / Q000379:methods; D032108:Salix / Q000502:physiology*; D012621:Seasons