Submitted to: CryoLetters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2005
Publication Date: 9/1/2005
Citation: Towill, L.E. and R.M. Bonnart. 2005. Cryopreservation of apple using non-desiccated sections from winter collected scions. CryoLetters 26:323-332. Interpretive Summary: Cryopreservation of apple germplasm can be accomplished by using winter- collected scions. One method requires desiccation of sections from these scions prior to slow cooling to '30oC and transfer to liquid nitrogen; however, the desiccation step is problematic. In this paper we show that desiccation of buds is unnecessary for survival of cryo-exposed apple buds from cold hardy germplasm. Sections cryopreserved could form a small sprout upon incubation of the scion in water. Buds from these sections could be grafted to form a shoot. Use of non-dried sections simplifies the cryopreservation protocol.
Technical Abstract: Winter vegetative buds of Malus species are cryopreserved at USDA-ARS NCGRP to backup important genetic resources maintained by field collections. The method uses desiccation of nodal sections prior to cooling. Although this method is valuable, desiccation is time and labor intensive, and can damage materials if excessive. This paper reports results of processing sections without desiccation to improve the efficiency of handling Malus accessions. Sections from mid-winter collected scions were cooled at different rates to -30°C or -35°C and transferred to the vapor phase over liquid nitrogen. Sections were warmed at +2°C and held overnight before testing viability. Viability was estimated using a sprouting test or a grafting test. Although samples were viable with a cooling rate of 1°C/h, slower cooling (5°C/day) improved survival for some accessions. Scions from three lines tested survived three cycles of cooling from +4°C to LN. Using a criterion of 50% or greater sprouting from LN-exposed sections, ten of twenty species had accessions that were successfully cryopreserved. Within a species, the percent of accessions successfully cryopreserved ranged from 25 to 100%.