Nicolás Saez

Bio: Nicolás Saez is an academic researcher from Pontifical Catholic University of Chile. The author has contributed to research in topics: Ceratobasidiaceae & Orchid mycorrhiza. The author has an hindex of 1, co-authored 1 publications receiving 26 citations.

Mycorrhizal fungi affect orchid distribution and population dynamics

Abstract: Symbioses are ubiquitous in nature and influence individual plants and populations. Orchids have life history stages that depend fully or partially on fungi for carbon and other essential resources. As a result, orchid populations depend on the distribution of orchid mycorrhizal fungi (OMFs). We focused on evidence that local-scale distribution and population dynamics of orchids can be limited by the patchy distribution and abundance of OMFs, after an update of an earlier review confirmed that orchids are rarely limited by OMF distribution at geographic scales. Recent evidence points to a relationship between OMF abundance and orchid density and dormancy, which results in apparent density differences. Orchids were more abundant, less likely to enter dormancy, and more likely to re-emerge when OMF were abundant. We highlight the need for additional studies on OMF quantity, more emphasis on tropical species, and development and application of next-generation sequencing techniques to quantify OMF abundance in substrates and determine their function in association with orchids. Research is also needed to distinguish between OMFs and endophytic fungi and to determine the function of nonmycorrhizal endophytes in orchid roots. These studies will be especially important if we are to link orchids and OMFs in efforts to inform conservation.

Altered rhizoctonia assemblages in grasslands on ex-arable land support germination of mycorrhizal generalist, not specialist orchids

Abstract: Species-rich seminatural grasslands in Central Europe have suffered a dramatic loss of biodiversity due to conversion to arable land, but vast areas are being restored. Population recovery of orchids, which depend on mycorrhizal fungi for germination, is however limited. We hypothesised that ploughing and fertilisation caused shifts in orchid mycorrhizal communities in soil and restricted orchid germination. We examined edaphic conditions in 60 restored and seminatural grasslands, and germination success in 10 restored grasslands. Using a newly designed primer, we screened the composition of rhizoctonias in soil, seedlings and roots of seven orchid species. Seminatural and restored grasslands differed significantly in nutrient amounts and rhizoctonia assemblages in soil. While Serendipitaceae prevailed in seminatural grasslands with a higher organic matter content, Ceratobasidiaceae were more frequent in phosphorus-rich restored grasslands with increased abundance on younger restored sites. Tulasnellaceae displayed no preference. Germination success in restored grasslands differed significantly between orchid species; two mycorrhizal generalist species germinated with a broad range of rhizoctonias at most restored grasslands, while germination success of specialists was low. Past agricultural practices have a long-lasting effect on soil conditions and orchid mycorrhizal communities. Altered mycorrhizal availability may be the main reason for low germination success of specialist orchid species.

Orchid Mycorrhizal Interactions on the Pacific Side of the Andes from Chile. A Review

Abstract: In order to confront the constant decline in global biological diversity, amelioration strategies are needed for threatened species to design reintroduction policies, particularly in plants with critical reproduction steps, such as orchids. Orchids are part of a highly diverse plant family, with several species under imminent extinction risk. This is the case of Chilean Orchidaceae, which has shown a constant decay in their populations due to an increase in the alteration processes of their natural distribution habitats. Successful orchid reintroductions require a full understanding of orchid mycorrhizal fungi and their dynamic according to different developmental stages and environmental conditions because orchid seeds need mycorrhizal fungi to obtain nutritional compounds at early developmental stages. This article performed a critical literature review of the ecological studies conducted on Chilean orchids and their relationships with mycorrhizal fungi in order to focus on the best scientific approach to achieve successful restoration programs involving orchid seeds and compatible mycorrhizal fungi.

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.