Cryopreservation of Ancient Apple Cultivars of Veneto: a Comparison between PVS2-Vitrification and Dormant-Bud Techniques

Abstract

A comparison between the PVS2-vitrification and the dormant-bud techniques for cryopreservation of ancient apple cultivars, recovered in Veneto (North-East of Italy) and preserved in the field by the Veneto Agricoltura regional agency, is described. In the PVS2-vitrification method, in vitro shoot tips were cold hardened (4 degrees C) for 2 days, exposed to a pre-loading solution (2 M glycerol and 0.4 M sucrose) for 30 min at 25 degrees C, treated with PVS2 for 60 or 90 min at 0 degrees C and then directly immersed in liquid nitrogen. After thawing and plating, the best survival rates for 3 ancient apple cultivars ('Campanin', 'Rosetta Mantovana' and 'Pom dell'Oio') were 57 to 100%. The dormant-bud protocol was based on winter collection of scions from which 35 mm uni-nodal sections were cut, desiccated, slow cooled (-1 degrees C/h) down to -30 degrees C, stored in liquid nitrogen, thawed, re-hydrated and used for vegetative propagation by chip budding. Out of the three tested cultivars ('San Piero', 'Canada Ruden' and 'Rosa Gentile'), the best result was achieved with 'San Piero', with 100% plant recovery when buds desiccated to either 30 or 26% moisture content prior to cryopreservation were used for chip budding. A cost-benefit analysis of the two cryopreservation techniques showed that the dormant-bud method was most effective in terms of time and labour. This outcome is discussed critically, considering many of the parameters that influence time and labour estimations.