Morphological and molecular characterization of mycorrhizal fungi isolated from neotropical orchids in Brazil

Abstract

To initiate a conservation program of the Orchidaceae from the Brazilian Atlantic rain forest with the purpose of ex situ conservation or reintroduction in the State of Minas Gerais, seven mycorrhizal Rhizoctonia-like fungal strains were isolated from roots of seven neotropical orchid species from three different Atlantic rain forest fragments. Taxonomic studies revealed that the isolates belong to the genera Ceratorhiza and Epulorhiza. The Epulorhiza isolates were identified as Epulorhiza repens (N. Bernard) R.T. Moore and Epulorhiza epiphytica Pereira, Rollemberg et Kasuya. RAPD analysis indicated higher polymorphism between Epulorhiza epiphytica and Epulorhiza repens than found in the PCR-RFLP analysis. RAPD and morphological analyses indicated a degree of relatedness among the Ceratorhiza isolates obtained from the roots of different Oncidium species. A combination of morphological and molecular characterizations permitted integration of fungal strain identification with genetic relatedness among the isolates, thus allowing some inferences to be made on specificity of these endosymbionts under field conditions. Résumé : Les auteurs travaillent à mettre sur pied un programme de conservation pour les Orchidaceae de la forêt ombrophile atlantique du Brésil, avec l'objectif d'effectuer de la conservation ex situ et de la réintroduction, dans l'état de Minas Gerais. À cette fin, ils ont isolé sept souches de champignons de type Rhizoctonia, à partir de racines de sept espèces d'orchidées néotropicales, provenant de trois fragments différents de la forêt ombrophile de l'Atlantique. Les études taxonomiques révèlent que les isolats appartiennent aux genres Ceratorhiza et Epulorhiza. Ils ont identifié les isolats d'Epulorhiza comme Epulorhiza repens (N. Bernard) R.T. Moore et Epulorhiza epiphytica Pereira, Rollemberg et Kasuya. L'analyse RAPD montre un polymorphisme plus grand entre l'Epulorhiza epiphytica et l'Epulorhiza repens, que celui qu'on retrouve avec les analyses PCR-RFLP. Les analyses RAPD et morphologiques indiquent un certain degré de relation entre les isolats provenant des Ceratorhiza obtenus des racines de différentes espèces d'Oncidium. La combinaison des caractéristiques morphologiques et moléculaires permet d'intégrer l'identification des souches fongiques avec la relation génétique entre les isolats, permettant ainsi de déduire des informations sur la spécificité de ces endosymbiontes, sous des conditions de terrain.

Germinação de sementes e desenvolvimento de protocormos de Epidendrum secundum Jacq. (Orchidaceae) em associação com fungos micorrízicos do gênero Epulorhiza

“…1; Pereira et al 2009). Outros trabalhos buscaram isolar fungos presentes em protocormos e plântulas coletadas no campo ou a partir de protocormos obtidos após incubação de sementes das orquídeas de interesse no seu habitat natural (McKendrick et al 2002;Pereira et al 2005a).…”

“…A maioria dos fungos micorrízicos isolados de orquídeas é identifi cada como fungos semelhantes à Rhizoctonia ou rizoctonióides, sendo os principais gêneros Rhizoctonia, Ceratorhiza e Epulorhiza (Pereira et al 2005a;b;Dearnaley 2007). Estes fungos estão dispersos nos ambientes naturais, exercendo outros papéis ecológicos como saprófi tas, pató-genos ou simbiontes de espécies vegetais de outras famílias (Rasmussen 2002).…”

“…Apresenta fl oração durante todo o ano, o que, facilita sua identifi cação no campo. Os fungos do gênero Epulorhiza são os principais simbiontes dessa espécie em campos graminóides (Nogueira et al 2005;Pereira et al 2005a;2009), tendo sido identifi cados três grupos de fungos Epulorhiza spp., morfologicamente distintos, associados a quatro populações de E. secundum (Pereira et al 2009). …”

Characterization of seed germination and protocorm development of Cyrtopodium glutiniferum (Orchidaceae) promoted by mycorrhizal fungi Epulorhiza spp.

“…The degree to which tropical orchids utilize fungi is unclear, but we have attempted to understand the orchidmycorrhizal association in our studies by isolating and identifying fungal symbionts (Pereira et al 2003b;2005b;Valadares et al 2015), by germinating seeds of tropical orchids (Pereira et al 2005a;2011;Guimarães et al 2013) and by characterizing protocorm development. Histological studies have also contributed to understanding the mechanisms involved in the mycorrhizal association (Arditti 1992).…”

The epiphytic orchids Ionopsis utricularioides and Psygmorchis pusilla associate with different Ceratobasidium lineages at Valle del Cauca, Colombia

“…Recent studies have researched tropical orchids in South and Central America (Otero et al 2002;2004;Pereira et al 2005;Otero et al 2007;Otero & Bayman 2009;Pereira et al 2009;Valadares et al 2012;Oliveira et al 2014;Pereira et al 2014), but only one demonstrated ITS rDNA sequences from mycorrhizal fungi in Colombia (Mosquera et al 2010;. In Ecuador, Suarez et al (2006) isolated mycorrhizal fungi belonging to the genera Tulasnella and Sebacina.…”