Plant Tissue Cult. & Biotech. 24(2): 287-301, 2014 (December)

Cycads in vitro

Jaime A. Teixeira da Silva, Wynston Ray Woodenberg¹ and Songjun Zeng²

P. O. Box 7, Miki-cho post office, Ikenobe 3011-2, Kagawa-ken, 761-0799, Japan

Key words: Cycas revolute, Mature zygotic embryo, Plant growth regulator

Abastract

The Cycadales are a group of botanical and evolutionary importance; however, many species face the threat of extinction due to poaching and habitat destruction. The current investigation reviews previous work on in vitro production of cycads, which holds great potential for mass production and germplasm conservation of these unique plants. Megagametophytes and zygotic embryos have been used as explants in most studies, while seedling tissue and new leaf tissue of mature trees have also been used. Callus, coralloid roots and somatic embryos have been formed in vitro but direct organogenesis appears to be the most promising method for mass production and germplasm preservation of the cycads, as recent studies have reported the acclimatization of numerous plantlets less than 200 days after initial culture of zygotic embryos. Cycads have been referred to by Gilbert (1984) as living fossils because they are an ancient group of plants, the Cycadales being the oldest of the living members of the gymnosperms (Ikeno 1896) and are therefore an important group in the quest to unravel the mysteries of plant evolution. Cycads are made up of three families: Cycadaceae, Stangeriaceae and Zamiaceae (Chavez et al. 1998). In the Cycadales, Hill and Stevenson (1999) listed 273 tropical and subtropical species in 11 genera although Chavez et al. (1998) claim 132 species in 10 living families. Cycas revoluta Thunb., commonly known as Japanese sago palm, is probably the most researched member of the Cycadaceae family and is the oldest of the living cycads (Jones 1993). Native to southern China and Japan (Stevenson 1990), it has several characteristic botanical features: it is evergreen, has palm-like, pinnately divided, glossy green leaves

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