IN VITRO PROPAGATION OF 'FRANGIPANI'

Plumeria rubra (‘Frangipani’) belongs to the Apocynaceae (dogbane) family. Native to Central and South America, the genus includes deciduous shrubs and small trees. Commercial hybrids with a large chromatic range of flowers are cultivated as potted trees and flowered potted plants. In Sicily, P. rubra is widely diffused since its arrival in the early 1800s. However, the nursery market cannot satisfy the consumer demand due to lack of propagation material. The aim of the present study was to define an in vitro propagation protocol of a Plumeria rubra commercial hybrid, in order to obtain a massive plant production. A preliminary investigation evidenced that to establish an aseptic in vitro culture, the cuttings’ fresh weight should be less than 30% since a high content of the latex can markedly obstacle the explants sterilization protocol. The multiplication trial was carried out onto a gelled substrate using the Murashige and Skoog salt and vitamin medium enriched with 3% sucrose. Increasing concentrations (0-1-2-3 mg L-1) of BA and 2ip, separately or in mixture with 0.1 mg L-1 IAA were tested. For the rooting trial a half strength MS nutrient medium was used with the addition of different concentrations of IAA (0, 0.3, 0.6 or 0.9 mg L-1). The explants showed a low proliferative aptitude. The highest number of shoots was obtained with 2 mg L-1 BA in combination with IAA. The best rooting rate (4 roots/explant/month) was obtained on half strength MS medium enriched with IAA at 0.3 mg L-1. This preliminary experiment showed that apical dominance is presumably the main limit to establish an efficient micropropagation protocol of the species.