Negative effects on survival and performance of Norway spruce seedlings colonized by dark septate root endophytes are primarily isolate‐dependent

Abstract

Root endophytes are common and genetically highly diverse suggesting important ecological roles. Yet, relative to above-ground endophytes, little is known about them. Dark septate endophytic fungi of the Phialocephala fortinii s.l.-Acephala applanata species complex (PAC) are ubiquitous root colonizers of conifers and Ericaceae, but their ecological function is largely unknown. Responses of Norway spruce seedlings of two seed provenances to inoculations with isolates of four PAC species were studied in vitro. In addition, isolates of Phialocephala subalpina from two populations within and one outside the natural range of Norway spruce were also included to study the effect of the geographic origin of P. subalpina on host response. The interaction of PAC with Norway spruce ranged from neutral to highly virulent and was primarily isolate-dependent. Variation in virulence was much higher within than among species, nonetheless only isolates of P. subalpina were highly virulent. Disease caused by P. subalpina genotypes from the native range of Norway spruce was more severe than that induced by genotypes from outside the natural distribution of Norway spruce. Virulence was not correlated with the phylogenetic relatedness of the isolates but was positively correlated with the extent of fungal colonization as measured by quantitative real-time PCR.

When the forest dies: the response of forest soil fungi to a bark beetle-induced tree dieback

“…The ecology of dark septate endophytes is relatively less well known than that of other rootassociated fungi. The effects of DSEs on spruce range from neutral to negative and are straindependent (Tellenbach et al, 2011;Reininger et al, 2012). The relative increase in dark septate endophytes 1 year after the tree dieback may indicate their use of dead spruce roots as a substrate for growth.…”

Arabidopsis thaliana model system reveals a continuum of responses to root endophyte colonization

“…Although many DSE fungi form similar morphological structures in the host roots (Jumpponen & Trappe 1998, Rodriguez et al 2009), they are taxonomically unrelated, vary in ecological or physiological functions and lead to variable host responses (Addy, Piercey & Currah 2005, Alberton, Kuyper & Summerbell 2010, Newsham 2011, Tellenbach, Grünig & Sieber 2011, Knapp, Pintye & Kovacs 2012. Our earlier studies in the tallgrass prairie concluded that while grasses overall tend to be colonized to a greater extent and respond more positively to DSE colonization, forbs also range from increased to no response to decreased biomass accumulation in their response to DSE fungi (Mandyam, Fox & Jumpponen 2012).…”

“…The outcomes of the symbioses may be influenced by the variability of component fungi (Munkvold et al 2004, Koch, Croll & Sanders 2006, Mandyam et al 2012, Tellenbach et al 2011 or host plants (Jones, Durall & Tinker 1990, Thomson et al 1994, Karst, Jones & Turkington 2009, Hoeksema et al 2010, as well as by abiotic variability in the availability of light or nutrients or in the stress under which the host-fungus symbiosis is evaluated (Johnson et al 1997, Redman, Dunigan & Rodrigues 2001, Rodriguez et al 2008, Johnson et al 2010, Newsham 2011. Compared to better known mycorrhizal symbioses or the vertically transmitted systemic foliar endophytes, the root-associated fungal endophytes have received little attention (Rodriguez et al 2009).…”

Plant–soil feedbacks promote negative frequency dependence in the coexistence of two aridland grasses

“…In arid grasslands, fungal communities in grass rhizospheres are dominated by dark septate endophytes, a polyphyletic group characterized by melanized, septate hyphae [27,28]. They may facilitate host water uptake, increase plant acquisition of organic nitrogen [29,30] or act as plant pathogens [31]. Arbuscular mycorrhizal fungi (AMF) also colonize grass roots at the Sevilleta [32].…”