Is the prominent ericoid mycorrhizal fungus Rhizoscyphus ericae absent in the Southern Hemisphere’s Ericaceae? A case study on the diversity of root mycobionts in Gaultheria spp. from northwest Patagonia, Argentina

Abstract

Ericaceae diversity hotspots are in the mountains of the Neotropics and Papua New Guinea, South Africa's fynbos and Southeast Asia but majority of references to their root mycobionts come from the Northern Hemisphere. Here, typical cultivable ericoid mycorrhizal (ErM) fungi comprise Rhizoscyphus ericae, Meliniomyces variabilis, and Oidiodendron maius. It is however unclear whether this is true also for the Southern Hemisphere. Our study focused on cultivable mycobionts from hair roots of Gaultheria mucronata and Gaultheria poeppigii (Ericaceae) from two natural forests in NW Patagonia, Argentina, differing in mycorrhizal preferences of their tree dominants. We detected 62 well-defined OTUs mostly belonging to Helotiales and Hypocreales; the most frequent were Phialocephala fortinii s. l., Pochonia suchlasporia, and Ilyonectria radicicola. Only one out of 257 isolates showed ITS nrDNA similarity to members of the R. ericae aggregate (REA) but was not conspecific with R. ericae, and only five isolates were conspecific with O. maius. Microscopic observations showed that the screened roots were frequently colonized in a manner differing from the pattern typically produced by R. ericae and O. maius. A re-synthesis experiment with selected isolates showed that only O. maius formed colonization resembling ericoid mycorrhiza. Amplification of root fungal DNA with REA-specific and Sebacinaceae-specific primers showed that REA mycobionts were present in some of the screened samples while Sebacinaceae were present in all samples. These results suggest that Gaultheria spp. from NW Patagonia form ericoid mycorrhizae predominantly with the difficult-to-cultivate Sebacinaceae while the incidence of REA is relatively low and may be masked by other most likely non-mycorrhizal cultivable mycobionts.

Experimental evidence of ericoid mycorrhizal potential within Serendipitaceae (Sebacinales)

“…5 years). The same methodology was also used in our previous study in NW Patagonia on Gaultheria roots, but despite detection of serendipitoid DNA using specific primers, no serendipitoid isolate was obtained (Bruzone et al 2015). In general, Ericaceae-associated Basidiomycetes grow slowly and commonly represent a minority of the cultivable mycobiont communities from Ericaceae hair roots, even when Ascomycetes-suppressing media are used for isolation.…”

“…In general, Ericaceae-associated Basidiomycetes grow slowly and commonly represent a minority of the cultivable mycobiont communities from Ericaceae hair roots, even when Ascomycetes-suppressing media are used for isolation. For example, using a benomylamended medium, Bruzone et al (2015) found that fastgrowing Ascomycetes still represented approx. 77 % of isolates from Gaultheria roots.…”

“…Serendipitaceae (hereafter, serendipitoids) are frequently detected in Ericaceae roots all over the world (Berch et al 2002;Allen et al 2003;Selosse et al 2007;Ishida and Nordin 2010;Wurzburger et al 2011;Setaro et al 2013;Bruzone et al 2015). Combined microscopic and molecular evidence suggests that they form ericoid mycorrhiza , an endomycorrhizal type specific to Ericaceae characterized by formation of hyphal coils within the rhizodermal cells of host thin roots, the so-called hair roots (Smith and Read 2008).…”

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

“…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].…”

Sexual and asexual states of some endophytic Phialocephala species of Picea

“…Cadophora, Leptodontidium, Microdochium, Periconia, Trichocladium) detected in roots of more than 600 plant species (Jumpponen andTrappe 1998, Knapp et al 2012). Fungi grouping with the PAC often are among the most abundant recovered from root systems using culture-dependent or culture-independent sampling methods (Bruzone et al 2015, Li et al 2015, Pickles et al 2015. The relationship between PAC species and their hosts is complex, with interactions ranging from pathogenic (Wilcox and Wang 1987, Stoyke and Currah 1993, Tellenbach et al 2011) to neutral or mutualistic (Fernando and Currah 1996, Vohník et al 2005, Peterson et al 2008, Newsham 2011, Otgonsuren and Lee 2012, Tellenbach and Sieber 2012.…”