Abstract
Arbutoid mycorrhizal plants are commonly found as understory vegetation in forests worldwide where ectomycorrhiza-forming trees occur. Comarostaphylis arbutoides (Ericaceae) is a tropical woody plant and common in tropical Central America. This plant forms arbutoid mycorrhiza, whereas only associations with Leccinum monticola as well as Sebacina sp. are described so far. We collected arbutoid mycorrhizas of C. arbutoides from the Cerro de la Muerte (Cordillera de Talamanca), Costa Rica, where this plant species grows together with Quercus costaricensis. We provide here the first evidence of mycorrhizal status for the Ascomycete Leotia cf. lubrica (Helotiales) that was so far under discussion as saprophyte or mycorrhizal. This fungus formed arbutoid mycorrhiza with C. arbutoides. The morphotype was described morphologically and anatomically. Leotia cf. lubrica was identified using molecular methods, such as sequencing the internal-transcribed spacer (ITS) and the large subunit (LSU) ribosomal DNA regions, as well as phylogenetic analyses. Specific plant primers were used to confirm C. arbutoides as the host plant of the leotioid mycorrhiza.