Molecular evidence reveals fungi associated within the epiphytic orchid Laelia speciosa (HBK) SCHLTR

Abstract

Fungi-orchid relationships have been studied mainly in terrestrial orchids. The present work deals with diversity and biological role of the fungi associated to the epiphytic orchid Laelia speciosa through molecular evidence. ITS sequences confirmed fungal presence in roots, capsules, seeds and in vitro seedlings. None of the fungi found formed characteristic pelotons, so we do not assume they are mycorrhizal. We identified 18 taxa of fungi belonging to eight known genera (Alternaria, Curvularia, Cylindrocarpon, Fusarium, Myrmecridium, Neonectria, Penicillium, and Tetracladium) and unknown species of Atractiellales, Helotiales, Hypocreales, Lasiosphaeriaceae, Nectriaceae, Sordariomycetes, and Tricholomataceae. From these, we infer the biology of nine parasites, four saprobes, and two endophytes. One of the fungi, a Helotiales species, was able to colonize all orchid tissues, including seeds and in vitro seedlings, so, even if all precautions were taken, "axenic culture" of L. speciosa is a difficult task. There is a considerable diversity of fungi within L. speciosa organs. Endophytic fungi interact with the whole plant of L. speciosa along its life cycle.