Plant regeneration from embryogenic tissue of Pinus luchuensis Mayr, an endemic species in Ryukyu Island, Japan

Somatic embryogenesis in Ryukyumatsu (Pinus luchuensis Mayr.), an endemic species in Ryukyu Island, Japan, was initiated from megagametophytes containing zygotic embryos on a medium supplemented with 10 µM 2,4-dichlorophenoxyacetic acid and 5 µM 6-benzylaminopurine. Embryogenic cultures were maintained and proliferated by subcultures at 2- to 3-week-intervals on the same fresh medium. The maturation of somatic embryos occurred on media containing maltose, activated charcoal, abscisic acid and polyethylene glycol. High frequencies of germination were obtained after the post-maturation treatment of somatic embryos under conditions of high relative humidity, and around 90% of them were converted into plants. Growth of the somatic embryo-derived regenerated plants has been monitored in the field.