Mycorrhizal compatibility and symbiotic seed germination of orchids from the Coastal Range and Andes in south central Chile

Abstract

Little is known about Orchidaceae plants in Chile and their mycorrhizal associations, a key issue for designing protective actions for endangered species. We investigated root fungi from seven terrestrial orchid species to identify potential mycorrhizal fungi. The main characteristics of Rhizoctonia-like fungi were observed under light microscopy, and isolates were identified through PCR-ITS sequencing. Molecular identification of fungal sequences showed a high diversity of fungi colonizing roots. Fungal ability to germinate seeds of different orchids was determined in symbiotic germination tests; 24 fungal groups were isolated, belonging to the genera Tulasnella, Ceratobasidium, and Thanatephorus. Furthermore, dark septate and other endophytic fungi were identified. The high number of Rhizoctonia-like fungi obtained from adult orchids from the Coastal mountain range suggests that, after germination, these orchids may complement their nutritional demands through mycoheterotrophy. Nonetheless, beneficial associations with other endophytic fungi may also co-exist. In this study, isolated mycorrhizal fungi had the ability to induce seed germination at different efficiencies and with low specificity. Germin ation rates were low, but protocorms continued to develop for 60 days. A Tulasnella sp. isolated from Chloraea gavilu was most effective to induce seed germination of different species. The dark septate endophytic (DSE) fungi did not show any effect on seed development; however, their widespread occurrence in some orchids suggests a putative role in plant establishment.

Isolation and Identification of Endophytic Bacteria from Mycorrhizal Tissues of Terrestrial Orchids from Southern Chile

“…The sequences were aligned and edited using the ClustalX and BioEdit software [29,30]. The phylogenetic relationships were estimated using the neighbor-joining method in the MEGA X software [31], according to Herrera et al [32]. The obtained sequences were submitted to the GenBank database under the codes MK790613-MK790627.…”

Root-Associated Fungal Communities in Two Populations of the Fully Mycoheterotrophic Plant Arachnitis uniflora Phil. (Corsiaceae) in Southern Chile

“…Microscope slides were prepared to inspect the morphology of fungal colonization inside A. uniflora rhizomes according to Herrera et al [9] and visualized in a scanning electron microscope SU 3500 (Hitachi, Tokyo, Japan) at a work distance of 5-7.2 mm.…”

“…Mycoheterotrophic plants require compatible mycorrhizal fungi which provide carbon to the associated plant. The degree of heterotrophy varies according to the nature of the carbon requirements of the plant (fully or partially mycoheterotrophic) and may comprise fungal endophytes, plant pathogenic fungi, saprophytic fungi, arbuscular-and ectomycorrhizal-forming fungi, which are efficient for nutrient uptake from diverse surrounding plants or decaying woods [9][10][11][12].…”

New Insights into the Symbiotic Relationship between Orchids and Fungi

“…Endomycorrhizas can be further classified as ectendomycorrhizas, ericoid, arbutoid, monotropoid, orchid and arbuscular mycorrhizas based on the specificity of plant families and the type of internal hyphae [3,8]. Ectomycorrhizas are also alternatively represented as arbuscular mycorrhizas because the class is the most prevalent type of mycorrhizae, as shown in approximately 71% of all vascular plant species [1,9].The Orchidaceae is the largest family of flowering plants including over 700 genera and about 30,000-35,000 species and still hundreds of new species displaying variable floral features, lifestyles, habitat distributions and trophic patterns are being discovered and developed every year [10,11]. Mycorrhizas in orchid species are highly important throughout their whole life including germination and further development.…”

“…The Orchidaceae is the largest family of flowering plants including over 700 genera and about 30,000-35,000 species and still hundreds of new species displaying variable floral features, lifestyles, habitat distributions and trophic patterns are being discovered and developed every year [10,11]. Mycorrhizas in orchid species are highly important throughout their whole life including germination and further development.…”