Clonal propagation of <em>Trichocentrum stramineum</em> (Orchidaceae), a threatened species endemic to Mexico

Abstract

Background: Cloning techniques are applied to an endangered orchid species in order to reproduce individual plants and to preserve their genetic characteristics. Objectives: To establish a new protocol for clonal propagation of a threatened orchid of horticultural importance. Study species: Trichocentrum stramineum, a threatened orchid endemic to Mexico. Study site and duration: Totutla, Veracruz, Mexico. All experiments were designed and carried out at the Botanical Garden-UNAM and the IIAF-UMSNH over a course of six years. Methods: Seeds were germinated in a modified KC basal medium; protocorms and apical bud explants were obtained from the resulting in vitro plants and cultivated with or without plant growth regulators (PGRs). Both experimental groups were subcultured in order to evaluate the number of protocorm-like bodies (PLBs) and buds per explant. Results: On average, protocorms generated 51.2 and 54.1 PLBs in the absence or presence of 1 mg l-1 6-benzyladenine (BA), respectively, while 13.1 and up to 23.7 PLBs and / or shoots were observed on the apical bud explants in the absence or presence of 1 mg l-1 kinetin, respectively. In both cases, responses were direct, without the formation of an intervening callus. Approximately 200 PLBs were subcultured and developed into whole plants within 14 weeks. These were acclimatized to greenhouse conditions with a 90 % survival rate after 12 weeks. After 44 weeks, flowering was observed (3 %) individuals measuring at least 12 cm in height. Conclusions: The developed protocol proved to hold great potential for commercial propagation and conservation programs.

Keywords

• Apical bud
• Flowering
• PLB
• Protocorm