New mutualistic fungal endophytes isolated from poplar roots display high metal tolerance

Abstract

This study aimed to isolate, identify, and characterise metal-tolerant fungi colonising poplar roots at a metalcontaminated phytoremediation site. Poplar roots were colonised by arbuscular mycorrhizal, ectomycorrhizal, and endophytic fungi, and the species were determined by ITS molecular analyses. Eight different isolates were successfully isolated into pure culture. Three isolates belonging to the Helotiales (P02, P06) and the Serendipita vermifera species (P04) were highly tolerant to metals (Cd, Zn, Pb, and Cu) compared to the mycorrhizal Hebeloma isolates. The three isolates degraded complex carbohydrates, such as xylan and cellulose, indicating that they could partially degrade root cell walls and penetrate into cells. This hypothesis was confirmed by further in vitro re-synthesis experiments, which showed that the three isolates colonised root tissues of poplar plantlets whereas two of them formed microsclerotia-like structures. Taken together, these results suggest an endophytic lifestyle of these isolates. This is the first evidence of S. vermifera as a root endophyte of poplar. A new endophytic putative species belonging to the Helotiales and closely related to Leohumicola is also reported. Interestingly, and when compared to mock-inoculated plants, both P06 and P04 isolates increased the number of root tips of inoculated poplar plantlets in vitro. Moreover, the S. vermifera P04 isolate also increased the shoot biomass. The results are discussed in relation to the potential use of endophytic strains for tree-based phytoremediation of metal-contaminated sites.

Co-inoculation of Lolium perenne with Funneliformis mosseae and the dark septate endophyte Cadophora sp. in a trace element-polluted soil

“…Values observed in this soil were four to six times higher than in local reference agricultural soils as reported by Lamy et al (2006). The overall characteristics of the site have been provided previously (Lacercat et al, 2016;Foulon et al, 2016). The physico-chemical characterization of the soil (Table 1) was performed by the SADEF laboratory (Aspach-le-bas, France) (COFRAC certificate N° 1-0751).…”

Forest Tree Microbiomes and Associated Fungal Endophytes: Functional Roles and Impact on Forest Health

“…Likar & Regvar [243] found that DSEs reduced the metal uptake by the Salix caprea L. cuttings, thus suggesting a beneficial role for S. caprea in metal-enriched soils. Similarly, four fungal root endophytes were found to be highly tolerant to metals (Cd, Zn, Pb, and Cu), further highlighting the potential use of these endophytic strains for tree-based phytoremediation of metal-contaminated sites [244]. It is possible that under stressful environments, the interactions between plants and root fungal endophytes could switch from neutral to beneficial, and in that sense, could be counted as constituting a mutualistic relationship [245].…”

Inhabiting plant roots, nematodes, and truffles—Polyphilus, a new helotialean genus with two globally distributed species

“…A total of 21 isolates belonging to the DSE-2 group and two isolates belonging to the DSE-5 group sensu Knapp et al (2012) originating from different hosts and geographic regions (TABLE 1) were examined in the present study. The sampling sites were previously described in Kovács and Szigetvári (2002), Knapp et al (2012), Glynou et al (2015), Lacercat-Didier et al (2016 and Ashrafi et al (2017).…”

“…All those isolates were able to colonize roots of hybrid Populus in re-synthesis experiments. The clade including these and other sequences was described as a "new endophytic putative species belonging to the Helotiales" (Lacercat-Didier et al 2016).…”