IN VITRO PROPAGATION OF ADULT STRAWBERRY TREE (ARBUTUS UNEDO L.) THROUGH ADVENTITIOUS SHOOTS AND SOMATIC EMBRYOGENESIS

A method for induction of adventitious shoots and somatic embryogenesis (SE) of Arbutus unedo is presented. Semi-hard woody nodal segments were excised from adult donor tree (12 years old) and cultured for 6 weeks on Murashige and Skoog's (MS) medium without plant growth regulators (PGRs) for the induction of axillary shoots. The induced axillary shoots were then cultured for 8 weeks on MS medium supplemented with TDZ (0-4 mg l(-1)) for their multiplication. The best axillary shoot multiplication (3.9 shoots/explants) was achieved on MS medium supplemented with 3.0 mg l(-1) TDz. Calluses were induced from internodal segments excised from in vitro axillary shoots and cultured on MS medium supplemented with various concentrations and combinations of PGRs. Embryogenic calluses developed over a period of 14 days with the highest response (17 embryos/callus) at 5.0 mg l(-1) BA and 5.0 mg l(-1) NAA. Following induction, the calluses were proliferated on the same medium and somatic embryos at the globular, heart-shaped, torpedo, and cotyledonary stages developed after 35 days in culture. Plantlets developed at 95% on MS medium without PGRs. Non-embryogenic callusses developed clusters of shoot buds. A combination of 2 mg l(-1) BA and 0.5 mg l(-1) NAA promoted the highest number of adventitious shoots (5.3 shoots/callus).