Asymbiotic germination, effect of plant growth regulators, and chitosan on the mass propagation of stanhopea hernandezii (orchidaceae)

Abstract

Background: Stanhopea hernandezii was collected from natural habitat in Mexico for its beautiful fragrant flowers. Biotechnological strategies of propagation may satisfy the market demand and are useful for conservation programs. Hypothesis: Vigorous seedlings of S. hernandezii can be produced in vitro by asymbiotic seed germination techniques and the addition of chitosan to the culture medium in the temporary immersion system (RITA®) and in semi-solid medium systems. Methods: The first step was the in vitro germination of seeds obtained from a mature capsule of wild plants, followed by multiplication via adventitious protocorm induction known as protocorm-like bodies, using plant growth regulators. For this purpose, we utilized Murashige and Skoog (MS) basal medium amended with 0.5 mg/L α-Naphthaleneacetic acid, combined with different concentrations of 6- Benzylaminepurine (1, 3, and 5 mg/L). The following step comprised the growth and development of protocorms to obtain plantlets in RITA® flasks containing 250 mL of liquid MS medium combined or not with different chitosan concentrations (5, 10, 15, 20, and 25 mg/L). Results: The results showed that media supplemented with 5, 10, and 15 mg/L chitosan concentrations enabled the obtaining of a larger biomass with a range of 40-48 seedlings/RITA® and an average height of 13 mm. The last step was the development from seedlings into plantlets, the latter being, vigorous and achieving up to 100 % survival after 12 weeks of ex vitro cultivation. Conclusion: This paper describes an efficient process of asymbiotic germination and mass propagation of S. hernandezii, a vulnerable orchid species endemic to Mexico.