CONSERVATION OF BANANA GERMPLASM THROUGH CRYOPRESERVATION

Abstract

Since most banana landraces (Musa spp.) do not produce seed and are vegetatively propagated, germplasm must be maintained clonally. Therefore field and in vitro collections were established. Currently, the world's largest banana collection (1080 accessions) is kept as in vitro proliferating meristems under limited growth conditions at the laboratory of Tropical Crop Improvement of K.U.Leuven (Katholieke Universiteit Leuven, Belgium). Cryopreservation is a welcome alternative since during storage at ultra-low temperatures (-196°C), all metabolical, chemical and physical processes are arrested. As such, the material under storage does not need to be subcultured, thus avoiding risks of contamination and human error, and no somaclonal variation will take place. We developed an extremely simple cryopreservation system relying on a two-week-preculture phase of highly proliferating meristems on media with elevated sugar concentrations followed by rapid freezing in liquid nitrogen. This cryopreservation protocol was successfully tested on 20 accessions belonging to different genomic groups. Normal plants were regenerated from each of them. Regeneration frequencies vary from 7.4 to 68.9 %, depending on the cultivar. The mode of action of the sugar preculture phase with respect to the cryopreservation ability of different cultivars is under investigation. It is demonstrated that lipid, sugar and protein contents of non-precultured and sugar precultured plants differ.