Propagation deRicinodendronheudelotiipar bouturagein vitro

Abstract

Article original In vitro propagation of Ricinodendron heudelotii by cuttings. Abstract-Introduction. R. heudelotii (Euphorbiaceae) is a fruit tree of the tropical wet, dense forests, exploited by the local populations. The species is dioecious. The currently used regeneration by seeds is not easy and it involves a genetic heterogeneity of the descendants. Until now, the species' horticultural vegetative multiplication was especially based on the use of seedlings resulting from seeds. Our work aimed at developing an in vitro vegetative propagation method of selected adult trees of R. heudoletii. Materials and methods. Cuttings of 2 cm (one node with a single axillary bud) were taken on an adult plant of R. heudelotii, and then cultured, after sterilization, on a half-diluted Murashige and Skoog's medium. Various concentrations of kinetin were added to this basic medium (BM) to study the cytokinin effect on the bud bursting and the axillary bud development. In the same way, effects of benzylaminopurine (BAP) added to BM were studied in parallel on the proliferation of buds present at the level of the cutting node. Lastly, the cutting's rooting after culturing either on medium with kinetin or on medium with BAP was tested by transplanting cuttings onto BM enriched with naphthaleneacetic acid (NAA). Results. The 4.5 mg BAP•L-1 medium allowed the proliferation of 91% of the buds present at the node level on cuttings, with a maximum of 4.8 newly formed buds per cutting. However, the insulation of these buds on medium enriched with NAA did not allow the observation of root differentiation. Medium with 2.5 mg kinetin•L-1 supported bud bursting and the best development of axillary buds (71%). Transplanting onto medium with 2 mg ANA•L-1 supported the rooting of 72% of the cuttings cultured at the beginning on medium with kinetin, with a maximum of 6.3 roots formed by cutting. The acclimatization success rate of the regenerated vitroplants was 52.7%. Discussion and conclusion. By using media with kinetin and NAA, a maximum of 36 rooted R. heudelotii vitroplants were regenerated in 22 weeks from the 50 cuttings cultured. This propagation rate remains weak and, for an effective clonal propagation of the species, it will have to be improved with a vitroplant complementary production starting with proliferation of buds obtained on medium with BAP. Cameroon / Ricinodendron heudelotii / plant propagation / vitroplants / propagation by cuttings / buds / rooting Propagation de Ricinodendron heudelotii par bouturage in vitro. Résumé-Introduction. R. heudelotii (Euphorbiaceae) est un arbre fruitier des forêts denses humides, exploité par les populations locales. L'espèce est dioïque. La régénération par graines actuellement utilisée n'est pas aisée et elle entraîne une hétérogénéité génétique des descendants. Jusqu'à présent, la multiplication végétative horticole a surtout été basée sur l'utilisation de plantules issues des graines. Le but principal de notre travail a été de développer une méthode de multiplication conforme in vitr...