The giant mycoheterotrophic orchid Erythrorchis altissima is associated mainly with a divergent set of wood‐decaying fungi |
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| Authors: | Yuki Ogura‐Tsujita Gerhard Gebauer Hui Xu Yu Fukasawa Hidetaka Umata Kenshi Tetsuka Miho Kubota Julienne M.‐I. Schweiger Satoshi Yamashita Nitaro Maekawa Masayuki Maki Shiro Isshiki Tomohisa Yukawa |
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| Affiliation: | 1. Faculty of Agriculture, Saga University, Saga, Japan;2. Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany;3. Botanical Gardens, Tohoku University, Aoba‐ku, Sendai, Japan;4. Graduate School of Agricultural Science, Tohoku University, Osaki, Miyagi, Japan;5. Faculty of Agriculture, Kagoshima University, Korimoto, Kagoshima, Japan;6. Yakushima Yakutane‐goyo Reseaech Group, Yakushima‐machi, Kagoshima, Japan;7. Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Minami‐Josanjima, Tokushima, Japan;8. Faculty of Agriculture, Tottori University, Koyamaminami, Tottori, Japan;9. Tsukuba Botanical Garden, National Museum of Nature and Science, Tsukuba, Ibaraki, Japan |
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| Abstract: | The climbing orchid Erythrorchis altissima is the largest mycoheterotroph in the world. Although previous in vitro work suggests that E. altissima has a unique symbiosis with wood‐decaying fungi, little is known about how this giant orchid meets its carbon and nutrient demands exclusively via mycorrhizal fungi. In this study, the mycorrhizal fungi of E. altissima were molecularly identified using root samples from 26 individuals. Furthermore, in vitro symbiotic germination with five fungi and stable isotope compositions in five E. altissima at one site were examined. In total, 37 fungal operational taxonomic units (OTUs) belonging to nine orders in Basidiomycota were identified from the orchid roots. Most of the fungal OTUs were wood‐decaying fungi, but underground roots had ectomycorrhizal Russula. Two fungal isolates from mycorrhizal roots induced seed germination and subsequent seedling development in vitro. Measurement of carbon and nitrogen stable isotope abundances revealed that E. altissima is a full mycoheterotroph whose carbon originates mainly from wood‐decaying fungi. All of the results show that E. altissima is associated with a wide range of wood‐ and soil‐inhabiting fungi, the majority of which are wood‐decaying taxa. This generalist association enables E. altissima to access a large carbon pool in woody debris and has been key to the evolution of such a large mycoheterotroph. |
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| Keywords: | mycoheterotrophy mycorrhiza orchid stable isotope symbiotic germination wood‐decaying fungi |
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