Desiccation and cryopreservation tolerance of near mature seeds of Citrus garrawayae

The effect of desiccation and liquid nitrogen exposure on seeds of Citrus garrawayae F.M. Bailey was investigated to facilitate ex situ conservation. Near mature seeds demonstrated tolerance to desiccation to low moisture contents (8% moisture content) and liquid nitrogen exposure. Thermal analysis of seeds revealed the absence of phase transitions attributable to ice formation / melting in seeds dried to low moisture contents which coincided with maximal germination after liquid nitrogen exposure. Germination of seeds was achieved in vitro, seedlings were successfully acclimatized to the shade house, and these demonstrated phenotypically normal growth in the field. This study therefore reports a protocol for the cryopreservation of C. garrawayae seeds which, in conjunction with a previously published micropropagation system, allows in vitro propagation of the limited seed material available in this rare listed species (e.g. for restoration purposes).