12 Orchid Mycorrhizas: Molecular Ecology, Physiology, Evolution and Conservation Aspects

Dearnaley, J. D. W.; Martos, Florent; Selosse, Marc‐André

doi:10.1007/978-3-642-30826-0_12

Cited by 253 publications

(416 citation statements)

References 142 publications

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“…Fungos Micorrízicos de Orquídeas (FMOs) pertencem ao gênero Rhizoctonia sp. (Epulorhiza sp., e Ceratorhiza sp., dentre outras sinonímias) e fornecem benefícios às plantas tanto na germinação de sementes bem como na fase adulta (Rasmussen & Rasmussen 2009;Dearnaley et al 2012).…”

Section: Discussionunclassified

“…Na natureza, as orquídeas associam-se a fungos micorrízicos visando suprir a demanda por nutrientes tanto na germinação de sementes quanto no desenvolvimento inicial das plântulas (Rasmussen & Rasmussen 2009;Hossain et al 2010). Durante a associação micorrízica o fungo coloniza células das raízes formando pelotons (hifas enoveladas) que são digeridos pela orquídea que, em contrapartida, fornece nutrição e proteção ao fungo (Rasmussen & Rasmussen 2009;Dearnaley et al 2012). Os principais fungos micorrízicos obtidos de orquídeas no Brasil pertencem aos gêneros Rhizoctonia sp., Epulorhiza sp., e Ceratorhiza sp.…”

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Cultivo in vitro de Epidendrum nocturnum (Orchidaceae) ocorrente no Cerrado da região Centro-Oeste

et al. 2016

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ResumoAs orquídeas podem ser propagadas in vitro em meios de cultivo assépticos ou em simbiose com fungos micorrízicos. Epidendrum nocturnum ocorre em áreas de Cerrado e neste estudo objetivou-se a visualização de fungos micorrízicos em suas raízes bem como o cultivo assimbiótico de suas plântulas em diferentes meios e a micorrização in vitro. No desenvolvimento assimbiótico testou-se três meios de cultura em um ensaio e, em outro ensaio, foram testadas formulações alternativas do meio Knudson C modificado, com a adição de polpa de frutas. Fungos micorrízicos de orquídeas foram usados na micorrização in vitro. Pelotons foram visualizados nas raízes de E. nocturnum. O meio Knudson C modificado diferiu estatisticamente dos demais, nas duas intensidades luminosas, no primeiro ensaio. No segundo ensaio, após sete meses, os meios com formulação alternativa não diferiram estatisticamente entre si. Na micorrização in vitro as plântulas com o isolado fúngico En07 (Waitea circinata) apresentaram maior vigor visual em relação aos demais tratamentos, mas não houve diferença estatística com o controle. Os meios com formulação alternativa e o Knudson C modificado podem ser utilizados no desenvolvimento in vitro de E. nocturnum e o isolado En07 pode ser usado na micorrização visando estratégias de conservação desta orquídea. Palavras-chave: orquídea, desenvolvimento assimbiótico, micorrização, fungo. AbstractOrchids can be propagated in vitro in aseptic culture media or in symbiosis with mycorrhizal fungi. Epidendrum nocturnum occurs in areas of Cerrado and this study aimed to mycorrhizal fungi visualization in their roots and its asymbiotic growing their seedlings in different media and in vitro mycorrhization. In asymbiotic development was tested three culture in a test and, another test, alternative formulations of medium Knudson C modified with addition of fruit pulp. Mycorrhizal fungi orchids were used in in vitro mycorrhization. Pelotons were visualized in the roots of E. nocturnum. The medium Knudson C modified statistically different from the others, the two light intensities, in the first test. In the second test, after seven months, with the alternative formulation means were not statistically different from each other. In vitro mycorrhization plantlets with isolated fungal En07 (Waitea circinata) showed greater visual effect compared to other treatments, but there was no statistical difference with control. The media with alternative formulation and Knudson C modified can be used in vitro development of E. nocturnum, and the isolated fungal En07 can be used in order mycorrhization of this orchid conservation strategies.

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Section: Discussionunclassified

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Cultivo in vitro de Epidendrum nocturnum (Orchidaceae) ocorrente no Cerrado da região Centro-Oeste

et al. 2016

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“…Starting from early observations (Bernard 1909;Burges 1939), orchid mycorrhiza has often been portrayed as an example of parasitism because of the observation that the fungi occasionally attack and destroy the protocorm. This view was likely reinforced by the fact that the form-genus Rhizoctonia, comprising the most common symbionts of photosynthetic orchids (Dearnaley et al 2012), also included Rhizoctonia solani, one of the most destructive plant pathogens (Parmeter 1970). Rhizoctonia has been later recognized as a polyphyletic group, with mycorrhizal and pathogenic isolates in distinct teleomorphic fungal genera (Taylor et al 2002;Weiss et al 2004), but orchid mycorrhiza is still sometimes referred to as a highly antagonistic interaction mainly because phytoalexins and other antifungal proteins can be accumulated in the plant tissues (Wang et al 2001;Shimura et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Gene expression in mycorrhizal orchid protocorms suggests a friendly plant–fungus relationship

Perotto

Rodda

Benetti

et al. 2014

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Main conclusionOrchid mycorrhiza has been often interpreted as an antagonistic relationship. Our data on mycorrhizal protocorms do not support this view as plant defence genes were not induced, whereas some nodulinlike genes were significantly up-regulated.Orchids fully depend on symbiotic interactions with specific soil fungi for seed germination and early development. Germinated seeds give rise to a protocorm, a heterotrophic organ that acquires nutrients, including organic carbon, from the mycorrhizal partner. It has long been debated if this interaction is mutualistic or antagonistic. To investigate the molecular bases of the orchid response to mycorrhizal invasion, we developed a symbiotic in vitro system between Serapias vomeracea, a Mediterranean green meadow orchid, and the rhizoctonia-like fungus Tulasnella calospora. 454 pyrosequencing was used to generate an inventory of plant and fungal genes expressed in mycorrhizal protocorms, and plant genes could be reliably identified with a customized bioinformatic pipeline. A small panel of plant genes was selected and expression was assessed by real-time quantitative PCR in mycorrhizal and non-mycorrhizal protocorm tissues. Among these genes were some markers of mutualistic (e.g. nodulins) as well as antagonistic (e.g. pathogenesis-related and wound/stress-induced) genes. None of the pathogenesis or wound/stress-related genes were significantly up-regulated in mycorrhizal tissues, suggesting that fungal colonization does not trigger strong plant defence responses. In addition, the highest expression fold change in mycorrhizal tissues was found for a nodulin-like gene similar to the plastocyanin domaincontaining ENOD55. Another nodulin-like gene significantly more expressed in the symbiotic tissues of mycorrhizal protocorms was similar to a sugar transporter of the SWEET family. Two genes coding for mannose-binding lectins were significantly up-regulated in the presence of the mycorrhizal fungus, but their role in the symbiosis is unclear.

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“…The embryo develops and forms the protocorm, an achlorophyllous and heterotrophic stage of the orchid life cycle (Rasmussen & Rasmussen 2009;Dearnaley et al 2012). 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).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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Cyrtopodium glutiniferum is an endemic orchid of Brazil with potential medicinal and ornamental applications. As mycorrhizal fungi are essential for the initiation of the orchid life cycle, the aim of this study was to determine the strains of mycorrhizal fungi suitable for seed germination and protocorm development of C. glutiniferum and to characterize the symbiotic development of protocorms. Seeds of C. glutiniferum were inoculated with nine mycorrhizal fungi, Epulorhiza spp., Ceratorhiza spp., Rhizoctonia sp., originally isolated from Brazilian neotropical orchids. Only Epulorhiza isolates promoted seed germination and protocorm development. Three Epulorhiza isolates (M1, M6 = E. epiphytica, M20 = Epulorhiza sp.) promoted protocorm development until leaf production at 63 days. The protocorms are comprised of parenchyma cells delimited by a unistratified epidermis; the parenchyma cells of the upper part of the protocorms are smaller than those located more towards the base. Intact and digested pelotons were observed inside of protocorms implying that the seedlings were capable of mycotrophy. Additionally, the development of a bud primordium only occurred after colonization by fungus. This study suggests that C. glutiniferum has a preference for strains of Epulorhiza and that fungus digestion is essential to protocorm development.

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12 Orchid Mycorrhizas: Molecular Ecology, Physiology, Evolution and Conservation Aspects

Cited by 253 publications

References 142 publications

Cultivo in vitro de Epidendrum nocturnum (Orchidaceae) ocorrente no Cerrado da região Centro-Oeste

Cultivo in vitro de Epidendrum nocturnum (Orchidaceae) ocorrente no Cerrado da região Centro-Oeste

Gene expression in mycorrhizal orchid protocorms suggests a friendly plant–fungus relationship

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

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