Initial development of an in vitro propagation protocols for Caracas walnut Juglans venezuelensis, a critically endangered tree endemic to Avila National Park, northern Venezuela.

Abstract

In order to design a micropropagation protocol for Caracas walnut Juglans venezuelensis, (a critically endangered Venezuelan endemic) morphogenesis studies were performed based on different explants. The explants were cultivated in mediums with different combinations of growth regulators under various conditions of light and darkness. Using nodal and apical segments, aerial sprouts developed when using Thidiazuron (TDZ) with concentrations of 0.3, 1.2 and 3.0 mg/l, and Benzilamine Purine (BA) with concentrations ranging from 0.2 to 1.5 mg/l. Microshoots with a lateral bud, cultivated in a medium complemented with Indole Butyric acid (IBA) (0.01 and 0.05 mg/l) + BA (1.0 mg/l) and TDZ (0.01 and 0.02 mg/l), also developed aerial sprouts (later transferred to another cultivation medium to promote root growth). In addition, starting from foliar explants in a medium complemented with Kinetin (Kin) (1.0 mg/l) combined with Naphthaleneacetic acid (NAA) (0.1 mg/l), somatic embryos were developed in globular and torpedo states, as well as thick radical structures and several radical hairs. The formation of new sprouts, followed by rooting and the conversion from embryos to plants is a key factor yet to be achieved in order to produce stock for incorporation into reforestation programmes.