Asymbiotic seed germination, in vitro seedling development, and symbiotic acclimatization of the Mexican threatened orchid Stanhopea tigrina

Abstract

Stanhopea tigrina commonly known in Mexico as “cabeza de vibora” or “calaverita”, is an endemic orchid from the mountain cloud forest of this country and it is currently an endangered species. The objective of this study was to stablish an in vitro propagation system for S. tigrina in order to contribute to the development of alternatives in the preservation of this species. Therefore, seeds from a mature capsule were cultivated in a Murashige and Skoog basal medium. Then, 16-week-old seedlings, counting weeks from the moment of germination, were transplanted into several treatments fortified with organic extracts (OE) or 6-benzylaminopurine (BAP) to induce the proliferation of the seedlings. These treatments fortified with OE and 5.0 mg of L− 1 BAP developed 1.25 ± 0.35 shoots with no significant differences. For the rooting process, the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid were tested either alone or in combination with salicylic acid or coconut water. The addition of 100 mL L− 1 of coconut water, alone or in combination with 2.5 or 5.0 mg L− 1 of IAA auxin were the best treatments for root production. For the establishment of symbiotic acclimatization, the vitroplants were inoculated with fungal spore suspensions of Trichoderma hamatum and Penicillium sp. The vitroplants to which T. hamatum was added as a symbiote achieved 100% survival and developed an average height of 2.54 ± 0.33 cm. In conclusion, the in vitro propagation protocol proposed in this study was effective for the symbiotic obtaining and acclimatization of S. tigrina plants. Stanhopea tigrina is an endemic orchid to Mexico and currently threatened. This research was designed in order to contribute to its conservation through the use of plant biotechnology. In this study it has been shown that the use of organic extracts and symbiotic acclimatization with fungi can be a useful method to regenerate and massively propagate this orchid.