Endophytic Fungal Mutualists: Seed-Borne Stagonospora Spp. Enhance Reed Biomass Production in Axenic Microcosms

Abstract

Fungal endophytes mainly belong to the phylum Ascomycota and colonize plants without producing symptoms. We report on the isolation of seed-borne fungal endophytes from Phragmites australis (common reed) that were ascribed to the genus Stagonospora. Nested polymerase chain reaction (PCR) assays revealed that a Stagonospora sp. regularly colonized reed as shown for a period of three years. In spring, it was only detected in roots, whereas in autumn, it could frequently be found in all organs, including seeds. Microcosm experiments revealed that seeds harbored viable propagules of the fungus that colonized the developing germling, indicating vertical transmission. Endophytic growth was confirmed by immunofluorescence microscopy, reisolation of the fungus after surface sterilization, and PCR. Aseptic microcosms were established for studying fungal contributions towards host vitality. Several Stagonospora isolates enhanced reed biomass. Seed-borne endophytic Stagonospora spp. thus can provide improved vigor to common reed, which could be most important when seed-derived germlings establish new reed stands.Additional keywords: ITS phylogeny, Phaeosphaeria.Fungi living in close association with plants can have effects on their host that range from detrimental to beneficial, depending on the partners involved and additional biotic and abiotic factors. Mycorrhiza is a well-documented type of a symbiotic interaction that is found at roots of the majority of higher plants. It is well known that mycorrhizal fungi are important for retrieving nutrients from soil and allocating them to their hosts (Hodge et al. 2001;Landeweert et al. 2001;Sharma et al. 1997). Endophytes represent another type of a putative symbiotic interaction between fungi and plants. Endophytes live within plant tissue without producing overt symptoms. Endophytic fungi have been recovered from all vegetative organs and from a broad range of plants growing from tropical to alpine habitats, indicating that these associations are widespread in nature (Carroll 1988;Petrini et al. 1992). Endophytes represent a wide taxonomical range of fungi, mostly within the phylum Ascomycota. Caroll (1988) distinguished two types of endophytic mutualism. Constitutive endophytic mutualism is typified by a systemic infection of grasses in genera Festuca, Lolium, and a few others in the family Poaceae with fungi of the anamorph genus Neotyphodium and the corresponding teleomorph genus Epichloë (family Clavicipitaceae, phylum Ascomycota) (Schardl 2001). These fungi proliferate in infected plants and are often vertically transmitted by seeds to the next generation of the host. It has been shown that these fungi improve the vitality of their hosts by increasing resistance against grazing, insects, drought, and microbial parasites (Clay 1992;Leuchtmann 1992;Schardl 2001). Furthermore, they improve biomass production and nutrient status (Arachevaleta et al. 1989;Groppe et al. 1999;Latch et al. 1985;Malinowski et al. 2000). On the other hand, Caroll (1988) characterized inducible en...

Pythium phragmitis sp. nov., a new species close to P. arrhenomanes as a pathogen of common reed (Phragmites australis)

“…Wirsel et al 2001, Wong & Hyde 2001. Some fungal endophytes were found to have beneficial effects on reed performance in vitro (Ernst, Mendgen & Wirsel 2003). However, a contributing role of fungal pathogens in the dieback of reed has only rarely been addressed (e.g.…”

A community of unknown, endophytic fungi in western white pine

“…1). Endophytes can influence community biodiversity (2) or even directly enhance plant growth (3). In grasses (4) and other herbaceous plants (5), dominant endophytes are known to produce toxic alkaloids that deter or poison herbivores.…”

Diversity and antagonistic activity of endophytic fungi from sweet cherry and pepper

“…In addition to being required for the normal development of some plants, some Class 2 endophytes increase plant root biomass and confer tolerance to a variety of biotic and abiotic stresses such as disease, drought, desiccation, heat and salinity . Class 2 endophytes, like all endophytes, colonize plants via infection structures such as appressoria or by direct penetration of plant tissues via hyphae (Ernst et al, 2003). Growth through plant tissues is dominantly intercellular with little to no impact on host cells (Ernst et al, 2003); .…”

“…Class 2 endophytes, like all endophytes, colonize plants via infection structures such as appressoria or by direct penetration of plant tissues via hyphae (Ernst et al, 2003). Growth through plant tissues is dominantly intercellular with little to no impact on host cells (Ernst et al, 2003); . While there may be a low level of sporulation or appressorial formation in healthy plants these fungi rapidly emerge and sporulate during host senescence (Weber et al, 2005); .…”

“…Glomerella acutata develops on naturally infected fruit in two forms: conidial (Colletotrichum acutatum) and the ascigerous (Glomerella acutata), but it endophytic association with plant in tropical and temperate regions has been reported ; (Ernst et al, 2003). Davidiella sp., formerly known as a pathogen inducing fruit rot in date palm, has been indicated to colonize host plants as an endophyte from Antarctica to temperate flora (Weber et al, 2005); (Selosse et al, 2004); (Newsham, 2011).…”