Isolating ecological-specific fungi and creating fungus-seed bags for epiphytic orchid conservation

Abstract

More than 1/3 of Chinese native orchids are used as Traditional Chinese Medicine (TCM) including many species of Dendrobium, and these Dendrobium species have been massively collected. The restoration-friendly cultivation model, i.e. planting targeted species in natural settings, is considered a new conservation tool for these epiphytic medicinal orchids, especially for Dendrobium species. In this study, we set out to develop an easy-to-use solution for practice of restoration-friendly cultivation in D. officinale, an critically endangered orchid with high medicinal value. We isolated fungi both from naturally occurred protocorms and roots of adult plants, and successfully obtained nine orchid mycorrhizal fungi (OMFs). Among them, five OMFs have been experimentally tested to promote seed germination and seedling development, but varied greatly in effectiveness. The most effective fungus, Sebacinales LQ, could quickly promote seedling formation and development in D. officinale. The percentage of protocorm formation could reach 65.90 ± 5.1%, and 4.57 ± 1.3% of seeds developed into seedlings at 30 days after incubation. At 60 days after incubation, the protocorm formation (83.71 ± 2.9%) already reached culmination and the percentage of seedlings (68.19 ± 3.8%) approached to peak level in LQ treatment. The fungus-seed bags, containing mixtures of fungal powders of LQ strains and seeds of D. officinale, were used as propagules and released in the original habitats of D. officinale. After one year, the percentages of seedlings in fungus-seed bags ranged from 13.16 ± 1.1% up to 20.88 ± 2.2% at three sites, and most seedlings appeared seemingly healthy. The fungus-seed bags showed many advantages in practice, e.g., low-cost mass production, long term storage, convenient transportation, controllable seedling quantity and density, ease of use in the field, and environmentally-friendly biodegradable paper bags. This low-cost and easy-to-use method could well achieve the target of restoration-friendly cultivation in D. officinale, and has universal applications for conservation translocations of epiphytic orchid based on symbiotic seeds germination.