The Co-occurrence and Morphological Continuum Between Ericoid Mycorrhiza and Dark Septate Endophytes in Roots of Six European Rhododendron Species

Abstract

Ericaceae associate with a wide spectrum of root mycobionts, but the most common are ascomycetous ericoid mycorrhizal fungi and dark septate endophytes (DSE), followed by basidiomycetous fungi and glomeracean arbuscular mycorrhizal fungi. We investigated distribution and morphological diversity of ericoid mycorrhizae (ErM), DSE associations, ectomycorrhizae (EcM) and arbuscular mycorrhizae (AM) in hair roots of six European native Rhododendron species and found that i) while EcM and AM were absent, ErM and DSE associations were simultaneously present in all screened plants; ii) their levels were negatively correlated, suggesting Ericaceae preference for certain root-fungus association in certain habitats; iii) the highest ErM colonization occurred at sites in southern and central Europe, while the highest DSE colonization was found in a subarctic site in northern Finland and in a subalpine site in the Carpathians, suggesting a latitudinal/altitudinal shift in Ericaceae root-fungus associations; iv) some mycelia could simultaneously form structures corresponding to ErM and DSE association, which occasionally resulted in a unique ectendomycorrhizal colonization comprising an intercellular parenchymatous net and intracellular hyphal coils. These results indicate frequent interactions between ErM fungi and DSE in roots of European rhododendrons and a morphological continuum between ErM and DSE associations. The new ectendomycorrhizal type deserves further investigation.

Anatomically and morphologically unique dark septate endophytic association in the roots of the Mediterranean endemic seagrass Posidonia oceanica

“…the hyphal structure typical of ectomycorrhizal symbiosis (Danielson and Visser 1990;O 'Dell et al 1993;Fernando and Currah 1996;Münzenberger et al 2009;Lukešová et al 2015). Moreover, some authors hypothesized that the dense parenchymatous net on the root surface (also known as DSE labyrinthine tissue), detected here for the first time in a seagrass, may functionally parallel the Hartig net (O'Dell et al 1993;Fernando and Currah 1996;Wurzburger and Bledsoe 2001;Vohník and Albrechtová 2011). Due to its frequency in some of the P. oceanica roots screened, the functioning of this fungal Fig.…”

“…In the Northern Hemisphere, their communities in temperate, boreal and subarctic plants are frequently dominated by dark septate endophytes (DSE), a group of miscellaneous soil fungi producing dematiaceous septate hyphae and melanized intracellular microsclerotia (Sieber 2002;Addy et al 2005;Grünig et al 2008). Additionally, some of them have been reported to form extra-and intraradical hyphal structures similar to those produced by mycorrhizal fungi for communication and nutrient exchange with their hosts, including dense parenchymatous hyphal nets on the root surface and intracellular hyphal loops (Vohník et al 2003;Peterson and Massicotte 2004;Münzenberger et al 2009;Vohník and Albrechtová 2011;Lukešová et al 2015). Some authors even proved bi-directional nutrient flow between DSE and their host plants (Usuki and Narisawa 2007).…”

Communities of Cultivable Root Mycobionts of the Seagrass Posidonia oceanica in the Northwest Mediterranean Sea Are Dominated by a Hitherto Undescribed Pleosporalean Dark Septate Endophyte

“…Some DSE can form structures morphologically resembling hyphal interfaces produced by mycorrhizal fungi for communication and nutrient exchange with their host plant [52,57,58], and the DSE colonization pattern in P. oceanica roots reported by Vohník et al [22] comprises dense parenchymatous nets/hyphal sheaths on the root surface which may morphologically resemble hyphal mantles produced by some ectomycorrhizal fungi. On one hand, based on the microscopic observations, it seems plausible that this DSE association is formed by the pleosporalean mycobiont discovered in this study.…”

“…Since the pleosporalean mycobiont also produced thick, septate, a melanized hyphae, it can be ranked among DSE, a miscellaneous group of ubiquitous endophytes colonizing roots of most terrestrial plants [51][52][53]. Pleosporalean fungi are often reported as DSE in roots of plants from arid and semi-arid regions [54,55].…”

The effect of NP fertilization on European blueberry (Vaccinium myrtillus L.) development on cultivated land in mid-Norway

“…0.2-0.5 g (FW) from five plants per plot were washed free of the adhering soil, mixed to make a compound sample, cleared with 10% KOH 20 minutes at 121 • C, acidified 1 minute in 3% HCl and stained with trypan blue (0.05% solution in lactoglycerol) overnight at room temperature. The stained EB hair roots were examined for presence and extent of fungal colonization (ericoid mycorrhiza, dark septate endophytes; [27]); using an Olympus BX60 microscope equipped with DIC. Root samples were screened at 400× and 1000× magnification and the fungal colonization was estimated after screening 50 fields of view per each compound sample.…”