In Vitro Propagation, Genetic Assessment, and Medium-Term Conservation of the Coastal Endangered Species Tetraclinis articulata (Vahl) Masters (Cupressaceae) from Adult Trees

Tetraclinis articulata (Vahl) Masters is an endangered tree growing in coastal and arid environments that is widely exploited by the timber and resin industry, among other applications. In this context, the use of in vitro techniques is highly encouraged for its propagation. We present a protocol for micropropagation using twigs from adult trees as a source of explants. The Schenk and Hildebrandt basal medium (SH) supplemented with 30 g L-1 sucrose, 6.5 g L-1 plant agar, 4.0 mg L-1 6-benzyladenine (BA), and 0.05 mg L-1 1-naphthaleneacetic acid (NAA) provided the optimum multiplication rate (90.48 +/- 9.52 explants with basal shoots and 2.58 +/- 0.29 basal shoots per explant). Application of activated charcoal (AC) or 1/2 Knop solution in a liquid overlay produced significantly longer shoots. Supplementation of solid media with indole-3-butyric acid (IBA) or NAA gave low rooting percentages (<17%). Addition of 0.9 g L-1 AC improved rooting (40%) but rooting performance was optimal (66.7%) after a pulse treatment consisting of 4 h immersion in liquid SH medium without growth regulators, followed by 8 weeks of cultivation. Rooted microplants were successfully acclimatized (93.33%) in a peat moss and vermiculite mixture (1:1 v/v ratio). The genetic stability of the in vitro regenerated plantlets was confirmed using the randomly amplified polymorphic DNA (RAPD) technique. Explant survival and growth remained higher than 90% after 28 weeks of cold storage at both 4 degrees C and 10 degrees C. The protocol presented here allows for largescale T. articulata production and could be applied for both ex situ conservation strategies and industrial purposes.

Automated summary

This study presents a protocol for micropropagation of endangered Tetraclinis articulata using twigs from adult trees. The optimized basal medium and supplementation with growth regulators resulted in high multiplication rate and longer shoots. Addition of activated charcoal and a pulse treatment improved root formation, and the acclimatization success rate of rooted microplants was high. The protocol allows for large-scale T. articulata production for conservation and industrial purposes.