Are fungi from adult orchid roots the best symbionts at germination? A case study

Meng, Yuanyuan; Zhang, Wenliu; Selosse, Marc‐André; Gao, Jiang-Yun

doi:10.1007/s00572-019-00907-0

Cited by 45 publications

(41 citation statements)

References 40 publications

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“…Although less frequently studied, the germination enhancing the effects of endophytic and saprophytic fungi, such as Fusarium spp. or Mycena spp., have also been reported (Meng et al 2019). In this study, most of the isolated endophytes were associated with a limited number of orchid species, suggesting potential specific interactions between these endophytes and their hosts.…”

Section: Discussionsupporting

confidence: 65%

“…Members of Tulasnellaceae and Ceratobasidiaceae are among the most frequently reported mycorrhizal fungi associated with roots of epiphytic orchids (Sathiyadash et al 2020, Suárez et al 2006, and thus, have received most of the attention in orchid germination studies. However, orchid seed germination in nature likely involves other, and perhaps more complex, interactions with non-mycorrhizal fungi (Meng et al 2019), and even other types of organisms (Rasmussen et al 2015). Although the interactions between orchids and nonmycorrhizal microorganisms have been characterized concerning nutrient acquisition, growth stimulation, and pathogen protection processes (Rasmussen et al 2015, Strobel 2002, Yuan, Chen & Yang 2009, the role of this group of microorganisms during orchid seed germination remains less understood.…”

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confidence: 99%

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Endophytic fungi associated with roots of epiphytic orchids in two Andean forests in Southern Ecuador and their role in germination

et al. 2020

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Orchids are known to establish complex relationships with endophytic fungi throughout their life cycle, and particularly during germination of their reserves-deprived seeds. Characterizing generalist or specialist interactions between orchids and associated fungi is key to supporting orchid conservation efforts. Here, endophytic fungi associated with roots of epiphytic orchids were studied in two montane Andean forests in Southern Ecuador. Orchid root samples were collected from ten ~500 m2 plots distributed between two neighboring forests. Endophytic fungi associated with these roots were then isolated, cultured, and identified by sequencing of rDNA markers. In total, 52 pure isolates were recovered from the roots of 10 orchid species. These isolates were classified into nine taxonomic groups except for one isolate that remained unclassified. Most fungal isolates were found in roots of up to two different orchid species; however, Coprinellus radians was found in the roots of all sampled orchids. The potential of C. radians to promote germination of orchid seeds was tested in a separate assay using seeds from two orchid species different than those found in the experimental forest plots. Of the two C. radians isolates tested, one improved germination in the two orchids evaluated to a level about half of that observed in seeds germinated in nutrient-rich medium (Phytamax) and above the null germination observed in plates without the fungus. Together, these results revealed a generalist relationship between C. radians and all the studied epiphytic orchids and the potential role of this fungus as a promoter of orchid seed germination. Key Words: Agaricales, Epidendrum, symbiotic germination

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Section: Discussionsupporting

confidence: 65%

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confidence: 99%

Endophytic fungi associated with roots of epiphytic orchids in two Andean forests in Southern Ecuador and their role in germination

et al. 2020

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“…Symbiotic seed germination in orchids is a complex process, particularly in terrestrial orchids, where different factors affect germination success. Our results did not show a conserved mycorrhizal fungus capable of promoting embryo growth and differentiation, suggesting specific fungal partners for each orchid species, which is consistent with Meng et al [50], who showed that mycorrhizal fungi isolated from advanced seedlings are more efficient at inducing seed germination than fungi isolated from adult mycorrhizal roots of the terrestrial orchid Arundina graminifolia, a process that may explain the low germination rates obtained in our studies, especially in the plants from the Andean sites.…”

Section: Discussionsupporting

confidence: 91%

“…Similar results were reported in the orchids Bipinnula volckmannii and Bipinnula apinnula, despite the fact that mycorrhizal fungi isolated from adult roots (Ceratobasidium spp.) mostly fail to induce embryo growth and differentiation, suggesting that mycorrhizal fungi isolated from adult plants may not be as effective at inducing the germination and development of the protocorms as mycorrhizal fungi isolated from protocorms, such as was the case in the results of our study in orchids from the sampling sites near the Andean mountains [21,50]. Furthermore, temporal variations in mycorrhizal fungi must to be considered by the effect of the habitat conditions as well as neighboring plant species during the vegetative or reproductive growth of some terrestrial orchids [51,52], a process that has certainly influenced the presence of fungi in the orchid roots analyzed in our study.…”

Section: Discussionmentioning

confidence: 69%

Mycorrhizal Fungi Isolated from Native Terrestrial Orchids from Region of La Araucanía, Southern Chile

et al. 2020

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Mycorrhizal interactions of orchids are influenced by several environmental conditions. Hence, knowledge of mycorrhizal fungi associated with orchids inhabiting different ecosystems is essential to designing recovery strategies for threatened species. This study analyzes the mycorrhizal associations of terrestrial orchids colonizing grassland and understory in native ecosystems of the region of La Araucanía in southern Chile. Mycorrhizal fungi were isolated from peloton-containing roots and identified based on the sequence of the ITS region. Their capacities for seed germination were also investigated. We detected Tulasnella spp. and Ceratobasidium spp. in the pelotons of the analyzed orchids. Additionally, we showed that some Ceratobasidium isolates effectively induce seed germination to differing degrees, unlike Tulasnella spp., which, in most cases, fail to achieve protocorm growth. This process may underline a critical step in the life cycle of Tulasnella-associated orchids, whereas the Ceratobasidium-associated orchids were less specific for fungi and were effectively germinated with mycorrhizal fungi isolated from adult roots.

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“…The majority of orchids relies on insects for successful pollination and subsequent seed development (Tremblay et al, 2005), while mycorrhizal fungi are needed for seed germination, seedling recruitment, and growth to adult plants (Swarts and Dixon, 2009;Mujica et al, 2018;Rasmussen and Rasmussen, 2018). Because most orchid seeds are very small (microspermy) and lack sufficient resources, orchid seeds critically depend on mycorrhizal fungi for essential carbon, water, and mineral nutrients (Meng et al, 2019b;Yeh et al, 2019). Before they appear aboveground, orchids are completely reliant on fungi, a condition called initial mycoheterotrophy (Merckx et al, 2013;Jacquemyn and Merckx, 2019).…”

Section: Introductionmentioning

confidence: 99%

Co-Cultures of Mycorrhizal Fungi Do Not Increase Germination and Seedling Development in the Epiphytic Orchid Dendrobium nobile

2020

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Orchids are highly dependent on mycorrhizal fungi for seed germination and subsequent growth to a seedling as they provide essential carbon, water, and mineral nutrients to developing seeds. Although there is mounting evidence that orchid seeds are often colonized by multiple fungi simultaneously, most in vitro germination experiments focus on mycorrhizal monocultures and little is known about how mycorrhizal assemblages affect seed germination and growth of seedlings. In this study, we compared the effects of mycorrhizal monocultures and co-cultures on seed germination and seedling growth of the epiphytic orchid Dendrobium nobile. In situ baiting was used to isolate mycorrhizal fungi from protocorms for germination experiments. Germination experiments were conducted under two light regimes for 90 days. In total, five fungal strains were isolated from protocorms of D. nobile, indicating that the species was not highly specific to its fungal partners. Four strains (JC-01, JC-02, JC-04, and JC-05) belonged to the Serendipitaceae and one (JC-03) to the Tulasnellaceae. In vitro germination experiments showed that germination percentages were higher under light-dark conditions than under complete dark conditions, supporting previous findings that light facilitates germination in epiphytic orchids. While all strains were able to induce protocorm formation and growth into the seedling stage, large differences between fungal strains were observed. Co-cultures did not result in significantly higher seed germination percentages and seedling development than monocultures. Taken together, these results demonstrate that effects of fungal assemblages are not predictable from those of component species, and that more work is needed to better understand the role of fungal assemblages determining seed germination and subsequent growth under natural conditions.

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Are fungi from adult orchid roots the best symbionts at germination? A case study

Cited by 45 publications

References 40 publications

Endophytic fungi associated with roots of epiphytic orchids in two Andean forests in Southern Ecuador and their role in germination

Endophytic fungi associated with roots of epiphytic orchids in two Andean forests in Southern Ecuador and their role in germination

Mycorrhizal Fungi Isolated from Native Terrestrial Orchids from Region of La Araucanía, Southern Chile

Co-Cultures of Mycorrhizal Fungi Do Not Increase Germination and Seedling Development in the Epiphytic Orchid Dendrobium nobile

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