Cryopreservation of in vitro grown fern gametophytes

Two methods of protecting fern gametophyte tissues through exposure to liqu id nitrogen (LN) were examined. In vitro grown gametophytic tissues from si x fern species were exposed to LN after open drying or after encapsulation dehydration, with and without preculture on abscisic acid (ABA). Open dryin g itself decreased survival with little further effect from LN exposure, al though survival was somewhat improved by preculture on ABA. In contrast, en capsulated tissues survived drying and LN exposure at rates comparable to c ontrols (86-100%) irrespective of ABA preculture. Sucrose pretreatment of t he encapsulated tissues was important for their subsequent survival through these procedures. Tissues prepared by encapsulation dehydration were succe ssfully regrown after 3.5 years in LN storage. Thus, cryopreservation appea rs to be a technique which could he used for the stable preservation of in vitro cultures of fern gametophytes and for the long-term storage of rare o r endangered germplasm of ferns.