In vitro germination of strawberry tree (Arbutus unedo L.) genotypes: establishment, proliferation, rooting and callus induction

Strawberry tree (Arbutus unedo L.), an evergreen shrub, is a post-fire resprouting species in the Mediterranean maquis, relevant for its ornamental value and utilised for fruit, honey, charcoal and fodder production. Seed and cutting propagation is currently used by nurseries. This paper investigates in vitro establishment, shoot elongation, proliferation and rooting of strawberry tree in vitro germinated seedlings, as well as callus induction from different explants. The best results in terms of non infected seeds and germination rate were obtained by disinfecting seeds in a 7% NaClO solution for 1 min. Axillary shoot development was relevant on apices cultured in a WPM medium with 22.2 ?M BA. A light intensity of 25 ?mol·m-2·s -1, in comparison with 40 ?mol·m-2·s -1, increased shoot elongation and axillary bud formation. Genotype noticeably influenced axillary shoot formation. Microcuttings rooted better when pulsed with 0.3 or 0.6 mM IBA for 15 min as compared to continuative treatment and trasferred to auxin-free medium. Yellow friable calluses were obtained from internodes, foliar discs and root cuttings cultured in 1/2 N - MS basal salts and vitamins supplemented with zeatin (1 and 5 ?M) being the largest those derived from internodes and cultured with the highest zeatin level.