Cryopreservation of Embryogenic Cultures of Conifers

Abstract

The cryopreservation methodology, currently used for plant material, originates from the research done on animal cells and tissues. The epoch-making finding in cryobiology was that made by Polge et al. (1949), who demonstrated the ability of fowl spermatozoa to survive freezing at −79°C in 10–20% glycerol for up to ten weeks. Other classical studies on mammals are those of Lovelock and Bishop (1959) and Mazur (1963). Lovelock and Bishop (1959) investigated the effectiveness of cryoprotectants in modulating the rise in salt concentration during freezing, and Mazur (1963) focused on the effect of cooling rate and the likelihood of intracellular freezing. Cryopreservation studies on plant material started in the 1960’s when Sakai (1960, 1965) investigated the cryotolerance of twigs of woody plants. The woody plants investigated for cryopreservation studies in the 1970’s and 1980’s were thein vivo andin vitro material of fruit trees, such asMalus spp (Sakai & Nishiyama 1978, Katano et al. 1983, Kuo & Lineberger 1985, Tyler & Stushnoff 1988) andCitrus (Marin & Duran-Vila 1988), other woody perennials such asRubus spp. (Reed 1988) andVaccinium spp. (Reed 1989),Coffea arabica (Bertrand-Desbrunais et al. 1988),Morus bombycis (Yakuwa & Oka 1988) and the moncotyledons, includingElaesis guinensis (Grout et al. 1983) andPhoenix dactylifera (Tisserat et al. 1981). The first reports on cryopreservation of conifers were published in the late 1980’s, the target species beingPicea abies,Pinus taeda (Gupta et al. 1987) andPicea glauca (Kartha et al. 1988). During the 1990’s the number of target species, both deciduous woody plants (for review see Bajaj 1995, Ryynänen 1999) and conifers, has increased rapidly, partly, due to the increased emphasis on cryopreservation technology in gene conservation, biodiversity, and in maintaining juvenility.