Only a few fully mycoheterotrophic (MH) orchids are currently known to be mycorrhizal with saprotrophic, mostly wood-decomposing fungi, instead of ectomycorrhizal fungi. Lee et al. identify mycorrhizal fungi for seven MH orchid species growing in four humid and warm subtropical forests in Taiwan and find that six of them are mycorrhizal with saprotrophic fungi that are either wood- or litter-decaying. They conclude that MH orchids utilizing saprotrophic, non-Rhizoctonia fungi as a carbon and nutrient source are clearly more frequent than hitherto assumed, allowing them to thrive in deeply shaded, light-limiting forest understoreys even without support from ectomycorrhizal fungi.
Yung-I Lee, Chih-Kai Yang, Gerhard Gebauer, 2015, ' The importance of associations with saprotrophic non- Rhizoctonia fungi among fully mycoheterotrophic orchids is currently under-estimated: novel evidence from sub-tropical Asia ', Annals of Botany, vol. 116, no. 3, pp. 423-435 http://dx.doi.org/10.1093/aob/mcv085