In vitro germination and induction of direct somatic embryogenesis in 'Bottle Palm' [Hyophorbe lagenicaulis (L.!Bailey) H.E.!Moore], a critically endangered Mauritian palm

Hyophorbe lagenicaulis is a critically endangered palm of Mauritius. Zygotic embryos were isolated from seeds and germinated in vitro on MS salts and vitamins containing activated charcoal. When seedlings were pre-treated in vitro for 2 weeks in liquid medium containing 0.05 mg 1(-1) paclobutrazol, 80% survived the transfer to soil. Three-week-old seedlings were sectioned longitudinally and partially embedded in medium that contained MS salts and vitamins, 30 g 1(-1) sucrose and 3 mg 1(-1) 2,4-dichlorophenoxyacetic acid. Somatic embryos were formed, in profusion, directly (without callus) from the haustorium, plumule and radicle. Direct regeneration is important for the conservation of endangered species, as fewer somaclonal variants are likely to arise than from indirect regeneration. When the haustorium, plumule and radicle of the longitudinally sectioned seedlings were separated, they formed more callus but fewer embryos. Plantlets derived from somatic embryos have not yet been successfully established in soil.