Total fatty acid composition in the characterization and identification of orchid mycorrhizal fungi Epulorhiza spp

Rhizoctonia-like fungi are the main mycorrhizal fungi in orchid roots. Morphological characterization and analysis of conserved sequences of genomic DNA are frequently employed in the identification and study of fungi diversity. However, phytopathogenic Rhizoctonia-like fungi have been reliably and accurately characterized and identified through the examination of the fatty acid composition. To evaluate the efficacy of fatty acid composition in characterizing and identifying Rhizoctonia-like mycorrhizal fungi in orchids, three Epulorhiza spp. mycorrhizal fungi from Epidendrum secundum, two unidentified fungi isolated from Epidendrum denticulatum, and a phytopathogenic fungus, Ceratorhiza sp. AGC, were grouped based on the profile of their fatty acids, which was assessed by the Euclidian and Mahalanobis distances and the UPGMA method. Dendrograms distinguished the phytopathogenical isolate of Ceratorhiza sp. AGC from the mycorrhizal fungi studied. The symbionts of E. secundum were grouped into two clades, one containing Epulorhiza sp.1 isolates and the other the Epulorhiza sp.2 isolate. The similarity between the symbionts of E. denticulatum and Epulorhiza spp. fungi suggests that symbionts found in E. denticulatum may be identified as Epulorhiza. These results were corroborated by the analysis of the rDNA ITS region. The dendrogram constructed based on the Mahalanobis distance differentiated the clades most clearly. Fatty acid composition analysis proved to be a useful tool for characterizing and identifying Rhizoctonia-like mycorrhizal fungi. Os fungos rizoctonioides são os principais fungos micorrízicos de orquídeas. A caracterização morfológica e a análise de sequências conservadas do DNA total são as principais estratégias empregadas na identificação e no estudo da diversidade desses fungos. Contudo, fungos rizoctonioides fitopatogênicos têm sido caracterizados e identificados, de forma confiável e precisa, pela determinação da composição de seus ácidos graxos. Com o objetivo de avaliar a utilização da composição de ácidos graxos na caracterização e identificação de fungos rizoctonioides micorrízicos de orquídeas, três fungos Epulorhiza spp., micorrízicos de Epidendrum secundum, dois fungos não identificados, isolados de Epidendrum denticulatum, e um fungo fitopatogênico Ceratorhiza sp. AGC foram agrupados com base no perfil de seus ácidos graxos, utilizando as distâncias euclidiana e de Mahalanobis e o método UPGMA. Os dendrogramas gerados possibilita