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

Abstract

ABSTRACT(Seed germination and protocorm development of Epidendrum secundum Jacq. (Orchidaceae) in association with Epulorhiza mycorrhizal fungi). In nature, species of Orchidaceae are always associated with mycorrhizal fungi. Th e comprehension of fungal-plant specifi city in this association can assist with the establishment of programs that focus on symbiotic propagation of orchids. Epulorhiza mycorrhizal fungi have frequently been isolated from Epidendrum secundum Jacq. Th us, the objective of this study was to evaluate the germination of E. secundum seeds and protocorm development associated with diff erent isolates of Epulorhiza spp. Sixteen Epulorhiza fungi obtained from diff erent E. secundum populations were used. Aft er 44 days, all isolates promoted seed germination of this species. However, differences were observed in the effi ciency in promoting seed germination and protocorm development, even among the isolates that had morphological similarities. Th e highest stage of protocorm development and the highest growth indexes were obtained in the presence of isolate M65. Th e results suggest that seed germination and protocorm development of E. secundum depend on the mycorrhizal fungi and, despite the high frequency of association between this plant and Epulorhiza, it is important to select isolates with high effi ciency to establish symbiosis. Effi cient isolates are useful for the production of seedlings that have economic and ornamental importance, as well as for endangered orchids.

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

“…1) confirms the dependence of C. glutiniferum seeds on mycorrhizal fungi to initiate germination. In some orchids, the seed embryo can intumesce (stage 1, Pereira et al 2011) or develop until the testa ruptures (stage 2, Peterson et al 1998) in symbiotic medium without fungi, but they develop no further. This development is the consequence of water imbibition, and the inoculation of a suitable symbiont can allow for the continuation of seed development (Peterson et al 1998).…”

“…These authors selected the Epulorhiza sp. isolate that had the best results in promoting seed germination of E. secundum (Pereira et al 2011).…”

“…Mycorrhizal colonization and fungi consumption persist in orchid roots into adulthood, when the interaction serves an important role in orchid nutrition (Dearnaley 2007;Rasmussen & Rasmussen 2009). Inoculation with mycorrhizal fungi has been applied to in vitro symbiotic seed germination and orchid cultivation (Pereira et al 2011;Guimarães et al 2013), with promising applications in the propagation of ornamental (Pereira et al 2003a;2005a), endangered (Zettler & McInnis 1992;Zettler et al 2007), and medicinal orchids (Chang & Chou 2001;Tan et al 2014).…”

“…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).…”

“…An alternative is to test mycorrhizal isolates obtained from other orchid species for their ability to prompt seed germination in C. glutiniferum, as proposed by Zettler (1997) and Zettler et al (1999). However, it is very important to select a fungus that establishes an association with the specific orchid species in order to achieve better results with symbiotic methods (Esitken et al 2005;Pereira et al 2005a;Brundrett 2007;Pereira et al 2011).…”