Cryopreservation of fruit and ornamental trees

Abstract

Non-forest woody plants include many fruit trees and ornamental plants. They not only provide delicious fruit but are also important as horticultural landscape plants. Conservation of these germplasm resources is necessary for the continued development of agriculture. As most species and cultivars of woody plants are genetically heterozygous, their genetic integrity must be maintained through vegetative propagation. The conventional method for woody plants is conservation in the field. However for longterm preservation of these genetic resources the field genebank is not only costly, because of the land and constant maintenance, but also susceptible to insects, diseases and environmental stress (Engelmann 2000; Reed et al. 2005). In-vitro cultured plantlets can be mass propagated with limited space and under disease-free conditions. Most cultures can be held under reduced or minimum growth conditions for years without reculture. Thus in-vitro plantlets are suitable materials for short- or medium-term backup storage of plant germplasm (Engelmann 2003; Reed and Chang 1997). Cryopreserved storage of plants in liquid nitrogen (LN) is the most promising approach to achieve long-term maintenance of woody plant germplasm (Sakai 1995). Cryopreservation can save labor and space, and it complements current germplasm storage methods, making it an important tool for long-term storage of vegetatively propagated plants (Engelmann 2000). Sakai (1960) first demonstrated that winter-hardy twigs survived after immersion in LN for 1 year. Since then many reports indicate that materials with meristems or embryogenic cultures of woody plants can be conserved successfully in LN (Kartha 1985, Sakai 1995, Reed and Chang 1997).