Conservation of tropical epiphytic orchids of commercial interest: development of technical protocols for symbiotic propagation through the application of mycorrhizal fungi.

The orchid family, Orchidaceae, is a group of highly attractive plants renowned for their exotic and colorful flowers, and of interest worldwide to horticulturists and plant collectors. Particularly in the neo-tropics, an over-reliance of orchid vendors on specimens collected from native habitats means many species are threatened with extinction in the wild. Illegal extraction, combined with general anthropogenic degradation of tropical ecosystems, make the Orchidaceae plant family a conservation priority worldwide. The majority of the more than 25000 orchid species are epiphytes native to tropical regions. Of the nearly 3500 species in Colombia, many are recognized internationally for their great ornamental potential. However, despite the commercial interest, efficient protocols for orchid propagation are lacking in many cases. In Colombia, the greatest floriculture interest focuses on the orchids of the genera Cattleya and Masdevallia spp., representing more than 50% of the Colombian orchid species threatened with extinction. For both conservation purposes, and to promote environmentally-responsible floriculture enterprises, it is desirable to develop protocols for the efficient propagation of these highly sought-after species. The use of in vitro tissue culture techniques has facilitated rapid propagation of some orchids from clonal tissue. Nonetheless, plant yield is often dramatically reduced during the crucial step of establishment of the plantlet in conditions ex vitro (hardening). Orchid propagation from seed has the advantage of maintaining the genetic diversity of artificial populations, both for commercialization, and particularly for natural population restoration. Orchid seeds are extremely small, lacking the endosperm store that usually provisions the embryo during the initial stages of germination. Instead, orchid seeds rely on a symbiotic interaction with mycorrhizal fungi to provide essential nutrients during the seed germination and seedling growth. Worldwide, only a few fungal taxa are associated with orchid mycorrhizae, mainly Tulasnella, Ceratobasidium and Sebacina. Relatively few studies have focused on the mycorrhizal interactions of tropical epiphytic orchid species, but some species studied show high levels of specificity for a particular fungal genotype, indicating that seed germination success may vary depending of the mycorrhizal fungi present. Protocols have been developed for asymbiotic seed germination for some tropical epiphytic orchid species, however it is likely that the presence of a mycorrhizal symbiont could enhance germination rates and also improve success during establishment ex vitro by enhancing nutrient delivery efficiency. During the course of research project #020100341 in 2013, we have isolated mycorrhizal fungi from Cattleya quadricolor and Masdevallia spp. In this current project we propose to evaluate the function of these cultured fungi in symbiotic seed germination protocols, and also in ex vitro plantlet establishment, in order to generate efficient technical protocols for the propagation and conservation of these orchids of high commercial interest. additionally, in order to enhance ex situ conservation initiatives we will evaluate protocols for long term storage of orchid seed and mycorrhizal fungi.