Progress and Prospects of Mycorrhizal Fungal Diversity in Orchids

Abstract

Orchids form mycorrhizal symbioses with fungi in natural habitats that affect their seed germination, protocorm growth, and adult nutrition. An increasing number of studies indicates how orchids gain mineral nutrients and sometime even organic compounds from interactions with orchid mycorrhizal fungi (OMF). Thus, OMF exhibit a high diversity and play a key role in the life cycle of orchids. In recent years, the high-throughput molecular identification of fungi has broadly extended our understanding of OMF diversity, revealing it to be a dynamic outcome co-regulated by environmental filtering, dispersal restrictions, spatiotemporal scales, biogeographic history, as well as the distribution, selection, and phylogenetic spectrum width of host orchids. Most of the results show congruent emerging patterns. Although it is still difficult to extend them to all orchid species or geographical areas, to a certain extent they follow the “everything is everywhere, but the environment selects” rule. This review provides an extensive understanding of the diversity and ecological dynamics of orchid-fungal association. Moreover, it promotes the conservation of resources and the regeneration of rare or endangered orchids. We provide a comprehensive overview, systematically describing six fields of research on orchid-fungal diversity: the research methods of orchid-fungal interactions, the primer selection in high-throughput sequencing, the fungal diversity and specificity in orchids, the difference and adaptability of OMF in different habitats, the comparison of OMF in orchid roots and soil, and the spatiotemporal variation patterns of OMF. Further, we highlight certain shortcomings of current research methodologies and propose perspectives for future studies. This review emphasizes the need for more information on the four main ecological processes: dispersal, selection, ecological drift, and diversification, as well as their interactions, in the study of orchid-fungal interactions and OMF community structure.

Orchidaceae-Derived Anticancer Agents: A Review

“…Considering the enormous number of orchid species, their symbionts remain poorly recognized. Noteworthy, most of the experiments on orchid endophytic fungi included only root tissue, [76,77] while in traditional medicine, stems, and leaves are organs usually used for therapies [43,48,49,[78][79][80][81]. The importance of recognition of orchid endophytic fungi for secondary metabolites synthesis and their potential application in medicine were summarized by Sarsaiya et al [39] and Pant et al [82].…”

Interaction With Fungi Promotes the Accumulation of Specific Defense Molecules in Orchid Tubers and May Increase the Value of Tubers for Biotechnological and Medicinal Applications: The Case Study of Interaction Between Dactylorhiza sp. and Tulasnella calospora

“…In general, mycorrhizal fungi supply plants with inorganic nutrients and water in exchange for carbohydrates. Conversely, this mutualism may occur even at an immeasurably low profit for fungi, and that is characteristic for orchidaceous mycorrhizae ( Li et al, 2021 ). Orchids start their lives as mycoheterotrophs and depend on their fungal benefactors.…”

Diversity of Root-Associated Fungi of the Terrestrial Orchids Gavilea lutea and Chloraea collicensis in a Temperate Forest Soil of South-Central Chile

“…Most of our understanding of the symbiotic associations of terrestrial orchids colonizing temperate forest ecosystems is from the northern hemisphere [ 17 , 18 , 19 ]. These studies have demonstrated the direct influence of the forest on the soil microbial communities and the preferences for specific mycorrhizal fungi [ 20 , 21 , 22 ]. Considerably less is known about terrestrial orchids, particularly those inhabiting the native temperate rainforest such as the Coastal Cordillera without volcanic influence and in the piedmont of Andes Cordillera with recent volcanic ash-derived soils in south-central Chile.…”