In vitro germination and development of three endangered species of Rubiaceae and Palmae from New Caledonia
New Caledonia is one of the world’s 34 biodiversity hotspots because of the originality of its flora. The 19 000 km2 island possesses 2432 endemic plant species growing among several natural vegetation types. Human activities have led to the reduction and fragmentation of these ecosystems, thus to the reduction of populations and specimen numbers, particularly the most original species. Our laboratory, has been working since 1996 on the multiplication, using in-vitro methods, of endangered species for their conservation and re-introduction in natural or artificial environments. This research is supported financially by two Provinces of New Caledonia and by a vast program dedicated to the "Sclerophyllous Forest Conservation".
Three species belonging to endemic genera are concerned : two critically endangered palms, Lavoixia macrocarpa and Pritchardiopsis jeanneneyi (from evergreen rain forests) and one endangered Rubiaceae, Captaincookia margaretae (from sclerophyllous forests), which seems interesting for rehabilitation and has a commercial potential. In both cases, we worked on seeds and/or on extracted embryos. Seed structures and embryo positions were described for the first time.
After optimising the disinfection methods, their germination on several media was investigated. In two cases, we obtained plantlets and in all cases embryogenic callus. We then tried to optimise the growth of plantlets before acclimatation. We also used callus, obtained either directly from embryos or produced from cotyledons, to regenerate an entire plant that could finally be acclimated.
The results we obtained were encouraging. On one hand, we managed to produce plantlets of L. macrocarpa and callus of P. jeanneneyi, and on the other, we have established a protocol to produce C. margaretea plants ready to be elevated in green house after acclimatation. These data are essential to prevent extinction of these particular species and for the conservation of New Caledonian ecosystems biodiversity.