In vitro propagation from axillary buds of the endangered tree Dalbergia congestiflora Pittier (Fabaceae)

Dalbergia congestiflora Pittier is a woody plant species grown in Mexico and Central America and widely used as timber wood and medicinal material. Since D. congestiflora is an endangered species, an in-vitro micropropagation technique is needed for mass propagation of D. congestiflora plantlets. Nodal segments of D. congestiflora stem cuttings grown in greenhouse conditions were disinfected with an appropriate protocol and in vitro established on Murashige and Skoog medium (MS) supplemented with 0.05 mg l^-1 benzylaminopurine (BA). The explants showed 10% contamination with 90% survival, and the initial shoot was regenerated in 90% of them. Axillary buds of 45-day-old initial shoots were cultured on MS containing BA (0, 0.05, 0.1, 0.5, 1, 1.5 and 2 mg l^-1) singly or in combination with α-naphthaleneacetic acid (NAA) (0, 0.1, 0.5 and 1 mg l^-1). A higher shoot number (9.6 shoots/explant) was obtained on MS with 1 mg l^-1 BA and 0.1 mg l^-1 NAA. Rooting was investigated using half-strength MS, 2% sucrose and different concentrations of indole butyric acid (IBA) (0, 0.1, 0.5 and 1 mg l^-1). After 30 days of culture, developing shoots were elongated and rooted in culture medium without IBA, with production of 3.2 roots/shoot. Micropropagated plantlets of D. congestiflora were successfully transplanted and acclimatized to a mixture of peat moss and perlite (2 : 1) with 100% relative humidity in greenhouse conditions with 80% survival at 30 days of culture. This micropropagation protocol will contribute to the conservation of D. congestiflora, and assure the mass propagation for sustainable usage of this species.