Asymbiotic and symbiotic seed culture of Polystachya concreta (Jacq.) Garay & H.R. sweet from Ecuador

Abstract

The Orchidaceae is the most numerous and diverse family in Ecuador with more than 4200 species. Information on the interaction between these neotropical orchids seed and mycorrhizal fungi during germination and seedling development in situ is very limited. Symbiotic seed germination culture allows screening for compatible mycobionts resulting in mycorrhizal associations to develop under sterile and controlled environmental conditions. A previously developed symbiotic seed culture protocol was used to screen seed germination and seedling development in the neotropical orchid Polystachya concreta. Mature seeds collected from native populations in the northwest Andes Mountains of Ecuador display high viability (92%) and germination percentage (96%). Light was not a limiting factor for gemination and seedling development in this orchid species. Tulasnella isolates from roots of different orchid species in situ facilitated seed germination only, whereas Tulasnella calospora (UAMH 9824), isolated from Spiranthes brevilabris in Florida, facilitated both seed germination and seedling development in P. concreta. Ceratobasidium strains, isolated from roots of different orchid species in Ecuador, neither promoted seed gemination or seedling development. Symbiotic seed culture did not significantly improve germination compared to that observed in the absence of fungi. Higher germination rates and percentages of more advanced seedling development were observed on asymbiotic PhytoTechnology Orchid Seed Sowing Medium (P723). However, significantly larger seeds seedlings were observed when seeds were cocultured with certain fungal isolates. Information obtained from this study confirm that this symbiotic seed culture application will be both beneficial for screening potential mycobiont isolates and seedling production for conservation of native orchid species in Ecuador.