Caracterização morfológica de fungos para a germinação in vitro de sementes de Cyrtopodium saintlegerianum Rchb. f. e Epidendrum nocturnum Jacq.(Orchidaceae), ocorrentes no bioma cerrado

• Autor(a) principal: Sousa, Kellen Cristhina Inácio de
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UFG
• Texto Completo: http://repositorio.bc.ufg.br/tede/handle/tede/9057
• topic: Germinação simbiótica; Especificidade micorrízica; Orquídeas tropicais; Symbiotic germination; Mycorrhizal specificity; Tropic orchids; GENETICA::GENETICA VEGETAL

In Brazil, 2500 to 3000 species of orchids have been reported to occur, of which 300 are found in the “cerrado” region. The orchids Cyrtopodium saintlegerianum (epiphyte) and Epidendrum nocturnum (rupicola) occur in areas anthropized of cerrado and cerrado rupestre, respectively. The orchids posses mycorrhizal association with rhizoctonia-like and endophytic fungi. The identification of these fungi can be done by microscopic and morphological characters. Root infecting fungi also are utilized for in vitro symbiotic germination of orchid seeds, aiming the conservation of plant species and fungi. The objective of the present investigation was isolation and morphological characterization of mycorrhizal and endophytic fungi originating from roots of C. saintlegerianum and E. nocturnum, as well as symbiotic in vitro seed germination. Three isolates of Epulorhiza sp. from each one of C. saintlegerianum, and E. nocturnum and two of Rhizoctonia sp. from E. nocturnum were obtained. Also, two isolates of Xylaria sp. were obtained from roots of C. saintlegerianum. There were, however, differences among isolates Epulorhiza sp. of C. saintlegerianum and of the E. nocturnum, in relation to morphological and enzymatic characters. The fungus was localized in root tissues of both species by optical and scanning electronic microscopes. The seed viability was tested by tetrazolium chloride and found 80.3 and 32.33% viable embryos of C. saintlegerianum and E. nocturnum, respectively. There was no in vitro symbiotic germination of E. nocturnum due to low seed viability. Two experiments of symbiotic germination of C. saintlegerianum seeds were conducted, both under photoperiods of 16/8 h (light/dark) at 26°C ± 2°C. The treatments were two isolates of Xylaria sp., three plant pathogens (Rhizoctonia solani of common beans and R. oryzae of rice ), and three mycorrhiza of C. saintlegerianum, two of Cyrtopodium vernum, and one ofE. nocturnum. Of three culture media tested, germination was obtained only in oat meal agar culture. The isolate En07 of Rhizoctonia sp. from E. nocturnum was found better for seed germination with 81.64 and 90.73% of germination of experiments 1 and 2, respectively. One non-specific isolate, two plant pathogenic isolates and one specific isolate were efficient for seed germination of C. saintlegerianum. On the other hand, for symbiotic in vitro seed germination of C. saintlegerianum, there was no specificity between this orchid and only one rhizoctonia-like fungus. These results showed that C. saintlegerianum can be propagated utilizing different root infecting fungi, which facilitates future programs of reintroduction and commercialization of species.