IN VITRO PROPAGATION OF MEXICAN RACE AVOCADO (PERSEA AMERICANA MILL. VAR. DRYMIFOLIA)

A protocol was developed for successful in vitro propagation of Mexican race avocado (Persea Americana Mill. var. drymifolia). Axillary buds were obtained from developing shoots of field grown trees in a germplasm bank (INIFAP, Uruapan, Michoacán, México). Explants were established on basal MS (Murashige and Skoog) medium containing 30 g/L sucrose, 1 g/L activated charcoal, 0.4 mg/L ascorbic acid, 1 g/L commercial fungicide Tecto 60 and gelled with 4 g/L phytagel. This medium was optimal for new shoot proliferation and elongation, the explants developing between 1-2 axillary new shoots after 45 days of culture. The in vitro response to hormones was evaluated subculturing the new shoots in MS medium supplemented with benzyladenine (BA) at 0, 0.25, 0.5, 1.0, 2.5 or 5.0 mg/L in combination with indol-3-butyric acid (IBA) at 0, 0.1, 0.25, 0.5 or 1.0 mg/L. The greatest percentage (71.3%) of shoot induction was achieved with 0.5 mg/L of BA and 0.1 mg/L of IBA, producing 3-5 shoots after 90 days of culture, with a maximum length of 2.25 cm. Rooting was readily achieved upon transferring the microshoots onto MS supplemented with 0.5 mg/L IBA after 90 days of culture. Micropropagated plantlets were acclimatized and successfully grown in greenhouse.