Diversidade e especificidade micorrízica em orquídeas do gênero Epidendrum

• Autor(a) principal: Pereira, Marlon Corrêa
• Data de Publicação: 2009
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1545
• topic: Epulorhiza; Ceratorhiza; Rhizoctonia; Opadorhiza-like; Fungos micorrízicos de orquídea; Fungos rizoctonióides; Epulorhiza; Ceratorhiza; Rhizoctonia; Opadorhiza-like; Mycorrhizal fungi to orchid; Rhizoctonia fungi; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::MICROBIOLOGIA AGRICOLA

Orchids are usually associated with Rhizoctonia-like mycorrhizal fungi belonging to Ceratorhiza, Epulorhiza and Rhizoctonia genera. These fungal symbionts have shown efficiency to promote seed germination and development of protocorms and seedlings. Epidendrum is a genus of orchid with the largest number of species, which are common in Atlantic Forest fragments and associate with Epulorhiza fungi. Thus, the objectives of this work were: (i) to compare morphological and molecular characteristics in the analysis of Rhizoctonia-like fungi diversity; (ii) to apply these characteristics in study of mycorrhizal diversity and specificity in Epidendrum secundum, natural from Serra do Brigadeiro State Park MG (SBSP), and in different orchids species of Epidendrum, from Atlantic Forest fragments located in Espírito Santo, Minas Gerais and Rio de Janeiro States; (iii) and to characterize orchid mycorrhizal fungi based on fatty acid composition. Qualitative and quantitative morphological characteristics were analyzed using multivariate techniques, distinguishing among Ceratorhiza, Epulorhiza and Rhizoctonia genera and different species of Epulorhiza spp. mycorrhizal fungi, which was confirmed by analyses of RAPD, ITS-RFLP and ITS rDNA sequence. A great diversity of Epulorhiza fungi and two Opadorhiza isolates were observed in eleven E. secundum populations located in different regions of campo de altitude of SBSP. However, the distinction between Epulorhiza and Opadorhiza, as well as among some Epulorhiza species, was possible just through analysis of ITS rDNA sequence. Sebacina and Tulasnella fungi, teleomorphs of the anamorphic genera Opadorhiza and Epulorhiza, respectively, were obtained from different species of Epidendrum studied. A great variability was observed on ITS sequence of Tulasnella spp. isolates, which formed nine clades. However, Sebacina spp. isolates showed lower variability in this sequence, forming only three clades. The analysis of fatty acid composition, using Mahalanobis distance and the UPGMA method, allowed the distinction between Epulorhiza and Ceratorhiza genera and among Epulorhiza spp. belonging to three different clades observed by the analysis of ITS sequence, demonstrating that the analysis of fatty acid composition is a useful tool to characterization and identification of Rhizoctonia-like mycorrhizal fungi of orchids. The morphological characteristics are important tools to distinction of some species and genera studied. It is suggest that Epidendrum orchids, even showing preference to Tulasnella/Epulorhiza fungi, do not present specificity to this fungal genus, because they associate with Sebacina/Opadorhiza fungi. This is the first report of association among Epidendrum orchids and Sebacina/Opadorhiza fungi.