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

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.

[1]  H. Jacquemyn,et al.  Fungi isolated from host protocorms accelerate symbiotic seed germination in an endangered orchid species (Dendrobium chrysotoxum) from southern China , 2020, Mycorrhiza.

[2]  J. Jersáková,et al.  Altered rhizoctonia assemblages in grasslands on ex-arable land support germination of mycorrhizal generalist, not specialist orchids. , 2020, The New phytologist.

[3]  K. Jahreis,et al.  The micorryzal fungi Ceratobasidium sp. and Sebacina vermifera promote seed germination and seedling development of the terrestrial orchid Epidendrum secundum Jacq , 2019, South African Journal of Botany.

[4]  M. Selosse,et al.  Are fungi from adult orchid roots the best symbionts at germination? A case study , 2019, Mycorrhiza.

[5]  H. Jacquemyn,et al.  Mycorrhizal symbioses and the evolution of trophic modes in plants , 2019, Journal of Ecology.

[6]  C. Yeh,et al.  New Insights into the Symbiotic Relationship between Orchids and Fungi , 2019, Applied Sciences.

[7]  Shengjie Liu,et al.  Do the fungi associated with roots of adult plants support seed germination? A case study on Dendrobium exile (Orchidaceae) , 2019, Global Ecology and Conservation.

[8]  D. Whigham,et al.  Mycorrhizal fungi affect orchid distribution and population dynamics. , 2018, The New phytologist.

[9]  N. S. Pradeep,et al.  Seed germination and seedling growth promoted by a Ceratobasidiaceae clone in Vanda thwaitesii Hook. f., an endangered orchid species endemic to South Western Ghats, India and Sri Lanka. , 2018 .

[10]  Kelly A. Carscadden,et al.  Using niche breadth theory to explain generalization in mutualisms. , 2018, Ecology.

[11]  H. Rasmussen,et al.  The epiphytic habitat on a living host: reflections on the orchid–tree relationship , 2018 .

[12]  L. Richardson,et al.  A comparision of ghost orchid (Dendrophylax lindenii) habitats in Florida and Cuba, with particular reference to seedling recruitment and mycorrhizal fungi , 2018 .

[13]  Hui Huang,et al.  Host-specificity of symbiotic mycorrhizal fungi for enhancing seed germination, protocorm formation and seedling development of over-collected medicinal orchid, Dendrobium devonianum , 2018, Journal of Microbiology.

[14]  G. Gebauer,et al.  Exploiting mycorrhizas in broad daylight: Partial mycoheterotrophy is a common nutritional strategy in meadow orchids , 2018 .

[15]  R. Brys,et al.  Mycorrhizal Associations and Trophic Modes in Coexisting Orchids: An Ecological Continuum between Auto- and Mixotrophy , 2017, Front. Plant Sci..

[16]  K. Burgess,et al.  Using In Situ Symbiotic Seed Germination to Restore Over-collected Medicinal Orchids in Southwest China , 2017, Front. Plant Sci..

[17]  B. Gravendeel,et al.  You are what you get from your fungi: nitrogen stable isotope patterns in Epipactis species , 2017, Annals of botany.

[18]  J. Men,et al.  Phylogenetic constrains on mycorrhizal specificity in eight Dendrobium (Orchidaceae) species , 2017, Science China Life Sciences.

[19]  R. Brys,et al.  Mycorrhizal specificity does not limit the distribution of an endangered orchid species , 2017, Molecular ecology.

[20]  S. Sede,et al.  Associated fungi, symbiotic germination and in vitro seedling development of the rare Andean terrestrial orchid Chloraea riojana , 2016 .

[21]  Ping Zhang,et al.  The dual inoculation of endophytic fungi and bacteria promotes seedlings growth in Dendrobium catenatum (Orchidaceae) under in vitro culture conditions , 2016, Plant Cell, Tissue and Organ Culture (PCTOC).

[22]  G. Gebauer,et al.  Partial mycoheterotrophy is more widespread among orchids than previously assumed. , 2016, The New phytologist.

[23]  M. Weiß,et al.  Sebacinales - one thousand and one interactions with land plants. , 2016, The New phytologist.

[24]  K. Dixon,et al.  Symbiotic seed germination of an endangered epiphytic slipper orchid, Paphiopedilum villosum (Lindl.) Stein. from Thailand , 2016 .

[25]  H. Jacquemyn,et al.  Specificity and localised distribution of mycorrhizal fungi in the soil may contribute to co-existence of orchid species , 2016 .

[26]  K. Yokoya,et al.  Non-specific symbiotic germination of Cynorkis purpurea (Thouars) Kraezl., a habitat-specific terrestrial orchid from the Central Highlands of Madagascar , 2016, Mycorrhiza.

[27]  Jiangyun Gao,et al.  Highly compatible Epa-01 strain promotes seed germination and protocorm development of Papilionantheteres (Orchidaceae) , 2016, Plant Cell, Tissue and Organ Culture (PCTOC).

[28]  R. Corlett,et al.  Orchid conservation in the biodiversity hotspot of southwestern China , 2015, Conservation Biology.

[29]  K. Dixon,et al.  Continent-wide distribution in mycorrhizal fungi: implications for the biogeography of specialized orchids. , 2015, Annals of botany.

[30]  K. Dixon,et al.  Germination and seedling establishment in orchids: a complex of requirements. , 2015, Annals of botany.

[31]  M. Selosse,et al.  Two widespread green Neottia species (Orchidaceae) show mycorrhizal preference for Sebacinales in various habitats and ontogenetic stages , 2015, Molecular ecology.

[32]  S. Sede,et al.  Mycorrhizal compatibility and symbiotic reproduction of Gavilea australis, an endangered terrestrial orchid from south Patagonia , 2014, Mycorrhiza.

[33]  H. Jacquemyn,et al.  What constrains the distribution of orchid populations , 2014 .

[34]  U. Goodale,et al.  In situ seed baiting to isolate germination-enhancing fungi for an epiphytic orchid, Dendrobium aphyllum (Orchidaceae) , 2014, Mycorrhiza.

[35]  C. Wang,et al.  In vitro seed germination and seedling growth of an endangered epiphytic orchid, Dendrobium officinale, endemic to China using mycorrhizal fungi (Tulasnella sp.) , 2014 .

[36]  P. Rudall,et al.  Taxonomy and Classification , 2013 .

[37]  J. Suda,et al.  Ploidy-specific symbiotic interactions: divergence of mycorrhizal fungi between cytotypes of the Gymnadenia conopsea group (Orchidaceae). , 2013, The New phytologist.

[38]  H. Lambers,et al.  Variation in nutrient-acquisition patterns by mycorrhizal fungi of rare and common orchids explains diversification in a global biodiversity hotspot. , 2013, Annals of botany.

[39]  Juan Chen,et al.  Isolation and identification of endophytic and mycorrhizal fungi from seeds and roots of Dendrobium (Orchidaceae) , 2011, Mycorrhiza.

[40]  R. Brys,et al.  Mycorrhizal associations and reproductive isolation in three closely related Orchis species. , 2011, Annals of botany.

[41]  L. Duan,et al.  In situ seed baiting techniques in Dendrobium officinale Kimuraet Migo and Dendrobium nobile Lindl. : the endangered Chinese endemic Dendrobium (Orchidaceae) , 2011 .

[42]  K. Dixon,et al.  Perspectives on orchid conservation in botanic gardens. , 2009, Trends in plant science.

[43]  Jason E. Stajich,et al.  The Fungi , 2009, Current Biology.

[44]  D. Read,et al.  Fungal specificity bottlenecks during orchid germination and development , 2008, Molecular ecology.

[45]  J. Arditti.  Factors affecting the germination of orchid seeds , 2008, The Botanical Review.

[46]  J. Zimmerman,et al.  Variation in sexual reproduction in orchids and its evolutionary consequences: a spasmodic journey to diversification , 2004 .

[47]  Nico Cellinese,et al.  Taxonomy and Classification , 2004 .

[48]  H. Rasmussen.  Recent developments in the study of orchid mycorrhiza , 2002, Plant and Soil.

[49]  M. Selosse,et al.  Chlorophyllous and Achlorophyllous Specimens of Epipactis microphylla (Neottieae, Orchidaceae) Are Associated with Ectomycorrhizal Septomycetes, including Truffles , 2004, Microbial Ecology.

[50]  John P. Huelsenbeck,et al.  MrBayes 3: Bayesian phylogenetic inference under mixed models , 2003, Bioinform..

[51]  M. Ellersieck,et al.  Symbiotic Seed Germination and Mycorrhizae of Federally Threatened Platanthera praeclara (Orchidaceae) , 2003 .

[52]  L. Adamec,et al.  Orchidaceae , 1995, Anatomic Atlas of Aquatic and Wetland Plant Stems.

[53]  H. Rasmussen.  Terrestrial Orchids: From Seed to Mycotrophic Plant , 1995 .

[54]  H. Rasmussen.  Terrestrial Orchids: From Seed to Mycotrophic Plant , 1995 .

[55]  D. Whigham,et al.  Seed ecology of dust seeds in situ: a new study technique and its application in terrestrial orchids , 1993 .

[56]  T. White.  Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics , 1990 .

[57]  W. A. Sledge.  An annotated check‐list of the Pteridophyta of Ceylon , 1982 .