A comparative study of the effects of the root endophytes Leptodontidium orchidicola and Phialocephala fortinii (Fungi Imperfecti) on the growth of some subalpine plants in culture

Abstract

Resynthesis studies were done to determine the ecological role of Leptodontidium orchidicola, a dematiaceous hyphomycete commonly associated with roots of plants growing in cool and humus-rich soils. Results were compared with those of Phialocephala fortinii, another common root endophyte with similar cultural and vegetative characteristics. In axenic culture with Salix glauca seedlings, L. orchidicola caused a marked increase in host root Length but also invaded the stele, causing extensive cellular lysis. Phialocephala fortinii formed a Hartig net and a thin, patchy mantle. In pot monocultures with Potentilla fruticosa, Dryas octopetala, S. glauca, and Picea glauca seedlings, the effects of four L. orchidicola strains on host dry weight were strain-and host-specific; the effects of Phialocephala fortinii were also host-specific. Leptodontidium orchidicola formed a range of symbiotic associations that could be considered mycorrhizal to parasitic, whereas the effects of Phialocephala fortinii suggest amensal, parasitic, or neutral association. In pot combination cultures, the Phialocephala fortinii -Potentilla fruticosa symbiosis resulted in a significant increase in shoot weight in contrast with the results of the same symbiosis in monoculture resynthesis. The resynthesis experiments demonstrated that the effects of both L. orchidicola and Phialocephala fortinii also vary according to cultural conditions. RQumC : Les auteurs ont conduit des Ctudes de resynthkse pour diterminer le rBle Ccologique du Leptodontidiurn orchidicola, un hyphomyckte dCmatiC communCment associC avec les racines des plantes poussant dans des sols froids, et riches en humus. 11s ont compare les rCsultats avec ceux obtenus avec le Phialocephala fortinii, un autre endophyte racinaire commun ayant des caractCristiques culturales et vCgCtatives similaires. En culture axinique avec des plantules de Salix glauca, le L. orchidicola provoque une forte augmentation de l'allongement des racines de I'hBte mais envahi Cgalement la stkle et cause une importante lyse cellulaire. Le Phialocephala fortinii forme un rCseau de Hartig et un mince manteau discontinu. En monoculture avec des plants de Potentilla fruticosa, Dryas octopetala, S. glauca et Picea glauca, les effets de quatre souches du L. orchidicola sur le poids sec des plants sont spCcifiques a la souche et a l'hBte; les effets du P. fortinii sont Cgalement spkcifiques l'h6te. Le L. orchidicola forme un ensemble d'associations qui peuvent &tre considCrCes comme allant de mycorhizienne a parasitaire, alors que les effets du Phialocephala fortinii suggkrent des relations amensales, parasitaires ou neutres. CombinCs en pots, la symbiose Phialocephala fortinii -Potentilla fruticosa conduit une augmentation significative du poids de la tige, contrairement a la resynthkse en monoculture de la m&me symbiose. Les experiences de resynthkse dCmontrent que les effets du L. orchidicola aussi bien que du Phialocephala fortinii varient selon les conditions culturales.

Paleomycology of the Princeton Chert II. Dark-septate fungi in the aquatic angiospermEorhiza arnoldiiindicate a diverse assemblage of root-colonizing fungi during the Eocene

“…Because the host-fungus interface of DSE involves a network of non-chitinous mucilaginous hyphae (Barrow 2003), direct evidence by which to discriminate an asymptomatic endophyte from a saprotrophic root colonizer is unlikely to be observed in the fossil record, although additional investigations may yield associated conidia. Conidiogenesis can be diagnostic for a number of root endophytes (Fernando andCurrah 1995, Addy et al 2005) but is often rare, frequently occurring only after a period of vernalization (Wilson et al 2004, Addy et al 2005. Because the sterile mycelia of most DSE are morphologically similar, we currently are unable to more precisely delimit the systematic affinities of these fossils, although the occurrence of two types of survival anamorphs indicates that more than one species of root colonizing fungi might have been present.…”

“…Instead, there is evidence that DSE are intimately associated with host sieve elements via mucilaginous hyphae that form integrated networks between the host's vascular system and the hyphae present within the cortical tissue (Barrow 2003). Intracellular microsclerotia occur in the outer cortex, developing in response to stress or host senescence (Fernando and Currah 1996, Jumpponen and Trappe 1998, Barrow 2003.…”

Sexual and asexual states of some endophyticPhialocephalaspecies ofPicea

“…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.…”

Diversidad, ecología e importancia potencial de los hongos endófitos septados obscuros en México

“…Los DSE Leptodontidium sp., L. orchidicola y Phialocephala fortinii han sido registrados como colonizadores de orquídeas como Calypso bulbosa (L.) Oakes, Coeloglossum viride (L.) Hartm., Corallorhiza maculate Raf. y Dendrobium nobile (Currah et al, 1987;Currah y Sherburne, 1992;Fernando y Currah, 1996;Hou y Guo, 2009). Se han encontrado, asimismo asociados con las raíces de equisetos (Equisetum spp.)…”