Somatic Embryogenesis and Regeneration of Endangered Cycad Species R.E. Litz and P.A. Moon V.M. Chavez Avila Tropical Research and Education Center Jardin Botanico, Instituto de Biologia University of Florida Universidad Nacional Autonoma de Mexico 18905 SW 280 Street Apartado Postal 70-614 Homestead FL, 33031-3314 USA 04510 Mexico DF Mexico Keywords: Somatic embryo, gymnosperm, Cycadales, conservation Abstract The Cycadales (Gymnospermae) include some of the world's most endangered and rare plant species. Many of the cycad species are known only as single specimen trees (e.g., Encephalartos woodii), as very small populations in the wild (e.g., Ceratozamia hildae) or have become extinct in the wild (e.g., Ceratozamia euryphyllidia). All cycads are dioecious, so that seed production is no longer possible with the rarest of the species. Conditions for induction of embryogenic cultures from leaves of mature phase trees of several species in the family Zamiaceae have been reported, and plants have been regenerated from somatic embryos. Embryogenic cultures of two species have been successfully cryopreserved. These strategies should contribute to the conservation of these endangered species and could lay the basis for commercial propagation of these beautiful but rare plants. INTRODUCTION The Cycadales represent the most ancient surviving group of higher plants, having arisen during the Permian era and flourished in the Mesozoic and Jurassic periods. They have been referred to as "living fossils" (Gilbert, 1984). Norstog (1987) considered that the cycads are unique for the study of the evolution of development in higher plants. There are only three extant cycad families, the Cycadaceae, Stangeriaceae and Zamiaceae, and these contain approximately 224 species. Cycads are generally restricted to tropical and subtropical regions. Many cycad species are extremely beautiful, and have either been collected to near-extinction or no longer exist in the wild, e.g., Encephalartos woodii, etc. The cycads are dioecious plants, and some of the rarest species are known only from specimen adult plants representing a single sex. All cycad species are considered to be in some way endangered, and the international trade of cycads has been curtailed by CITES regulations. Recent revisions to cycad taxonomy, together with increased plant exploration, have resulted in the recognition of several new cycad species (Hill and Stevenson, 1999). Many of these newly described species are confined to small habitats, whose precise locations have not been defined in order to provide some degree of protection from illegal collectors. Conservation of cycad species has been based upon the protection of their native habitats in situ or ex situ as living collections. In situ conservation has not been very effective for a few reasons: 1) habitats of many cycad species have been destroyed for subsistence agriculture; 2) large scale theft of rare species; and 3) the illegal international trade in rare species. It has been suggested that cycad conservation could be more effective if improved methods for propagating various species were developed (Dehgan, 1983; 1996a,b; 1999; Dehgan and Almira, 1993; Giddy, 1996). More efficient propagation methods could improve availability of rare cycads and thereby discourage theft from their native habitats. Dehgan (1999) proposed that this could be accomplished by improving seed production by hand pollination, better seed germination, root pruning in order to enhance vegetative growth rate, and enhanced procedures for vegetative propagation. In vitro regeneration of cycads has made some significant recent advances. In vitro studies involving cycads were initiated by LaRue (1948, 1954), who described the 75 Proc. IInd IS on Biotech. of Trop & Subtrop. Species Eds: W.-C. Chang and R. Drew Acta Hort 692, ISHS 2005