Ex situ seed baiting to isolate germination-enhancing fungi for assisted colonization in Paphiopedilum spicerianum, a critically endangered orchid in China

Using orchid mycorrhizal fungi to facilitate orchid recovery projects is considered to be an effective method for orchid conservation. In this study, we used ex situ seed baiting to isolate fungi to assist seed germination in Paphiopedilum spicerianum, a critically endangered orchid with only a single population found in south China. Two fungal species, GYBQ01 and GYBQ02, were successfully obtained and identified as belonging to Tulasnellaceae. Both fungi were capable of promoting seed germination up to the seedling stage, as the percentage of seedlings in GYBQ01 and GYBQ02 treatments reached 34.9 ± 2.7% and 50.8 ± 3.5%, respectively, at 120 days after incubation. Both fungi also showed a strong host-specific relationship with P. spicerianum. Using these fungi, we developed fungi-seed bags to be used as propagules for assisted colonization of P. spicerianum. This approach had 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 environmently-friendly biodegradable paper bags. This is the first time that this approach has been applied to assisted colonization of an endangered orchid, and has universal application to other orchids. Our results have potential to provide a complete solution for orchid reintroduction, as well as assisted colonization, based on symbiotic seed germination.