In vitro propagation of Picconia azorica (Tutin) Knobl. (Oleaceae) an Azorean endangered endemic plant species

Abstract

Picconia azorica (Tutin) Knobl. (Oleaceae) is a woody plant endemic from the Azores. It is considered as a part of a true relict taxon, reflecting its phylogeny, genetics and geography. Given the fragile status of this species, effective management and conservation are necessary for its survival and repopulation, initially for ecological reasons, but ultimately for forestry purposes as a valuable source of timber. Micropropagation is a useful tool for conservation programs, and in vitro culture techniques have, therefore, been developed for P. azorica by testing different combinations of media and growth regulators at each micropropagation stage. Adult plants from the field were successfully established in vitro on Rugini olive medium supplemented with 24.6 µM 2-isopentenyl adenine (2iP), resulting in 91.2 % sprouting of the nodal explants that survived the disinfection stage, although similar results were achieved using 18.2 µM zeatin. At the multiplication stage, the best shoot quality and the best compromise between shoot length and new axillary shoot development were achieved using the modified macronutrients Driver and Kuniyuki walnut medium supplemented with 24.6 µM 2iP and 0.6 µM indole-3 acetic acid. Rooting was most successful with half-strength macronutrients combined with 10 µM indole-3 butyric acid. Using this micropropagation protocol, a wide range of accessions were successfully established in vitro and are now being propagated on a larger scale for ecosystem restoration.