Micropropagation of strawberry tree (Arbutus unedo L.) from adult plants

Arbutus unedo L. is a species of strawberry tree, widely represented in the Mediterranean climates of southern Europe. Fruits are used to make jellies and a spirit called “medronheira.” Shoot apices and nodal segments from epicormic and coppiced shoots of adult plants were used for plant propagation. Shoot apices from epicormic shoots, which were developed in a growth chamber, showed higher rates of in vitro establishment. The results also indicated that shoot apices are more effective for plant establishment than nodal segments, with rates of establishment significantly higher after 12 wk of culture. Of the three basal media used in combination with 9.0 μM benzyladenine and 0.087 M sucrose, the FS medium with the micronutrients of the Murashige and Skoog medium gave the highest rates of multiplication, especially when the parameter analyzed was the number of clusters formed. When shoot apices from selected adult plants (AL01–AL06) were tested, the multiplication rate was not significantly different among the plants. However, in the conditions tested, shoots from the clones AL1, AL2, and AL3 showed better development, whereas shoots from AL4, AL5, and AL6 showed an impaired development and could not be rooted. Rooting was achieved in all the conditions tested, even in the absence of auxin. The inclusion of an auxin significantly increased root formation, whereas the addition of charcoal did not improve root formation. Rooted plantlets were acclimatized, and some of them are now in the field for further study.