Advances in the cryopreservation of fruit plant germplasm at the CNR-IVALSA Institute of Florence.

Cryopreservation allows the conservation of organs and tissues from in vitro culture (e.g., shoot tips, embryogenic callus, somatic embryos) in liquid nitrogen, as well as the conservation of in vivo collected material (seeds and buds). Working with vegetatively-propagated fruit species, the cryopreservation of shoot tips, using PVS2-based vitrification procedures, still remains the most commonly used approach. However, for specific applications there are also other techniques available today. Among them, the storage in liquid nitrogen of dormant buds has already proved to be effective for the long-term conservation of apple germplasm. Experiments in this direction are in progress at the CNR-IVALSA with ancient apple cultivars from the Veneto region. The protocol is based on winter collection of scions from which uni-nodal sections are cut, desiccated, slow cooled up to -30°C, stored in liquid nitrogen, thawed, re-hydrated and used for vegetative propagation by chip budding. The best result was achieved with the 'San Piero', for which 100% of the plants regrew successfully when both 30%- and 26%-desiccated and cryopreserved buds were used for chip budding on clonal rootstocks. As for seed cryopreservation, an effective procedure by 'desiccation/one-step freezing' has been developed for polyembryonic seeds from an ancient Citrus collection located in a Medicean Villa of Florence.