Ericoid plant species and Pinus sylvestris shape fungal communities in their roots and surrounding soil

Abstract

Root-colonizing fungi can form mycorrhizal or endophytic associations with plant roots, the type of association depending on the host. We investigated the differences and similarities of the fungal communities of three boreal ericoid plants and one coniferous tree, and identified the community structure of fungi utilizing photosynthates from the plants studied. The fungal communities of roots and soils of Vaccinium myrtillus, Vaccinium vitis-idaea, Calluna vulgaris and Pinus sylvestris were studied in an 18-month-long experiment where the plants were grown individually in natural substrate. Photosynthates utilizing fungi were detected with DNA stable-isotope probing using CO ( C-DNA-SIP). The results indicated that the plants studied provide different ecological niches preferred by different fungal species. Those fungi which dominated the community in washed roots had also the highest C-uptake. In addition, a common root endophyte without confirmed mycorrhizal status also obtained C from all the plants, indicating close plant-association of this fungal species. We detect several fungal species inhabiting the roots of both ericoid mycorrhizal and ectomycorrhizal plants. Our results highlight that the ecological role of co-occurrence of fungi with different life styles (e.g. mycorrhizal or endophytic) in plant root systems should be further investigated.

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

“…Sieber species complex (PAC), and they are among the best-characterized DSEs [95][96][97][98][99][100][101][102]. The PAC members are very widespread and abundant in the roots of ericaceous plants and conifer trees [18,96,98,[103][104][105][106]. Members of PAC species complex cannot be differentiated based on morphology.…”

“…Generally, DSEs do not have host specificity; however, there are some species that seem to prefer certain host taxa e.g., Cadophora, Cryptosporiopsis, and some of the PAC species (Acephala applanata Grünig & T.N. Sieber) preferentially occur on family Pinaceae [18,20,92,96,[105][106][107]. Despite the apparent abundance of Class 4 endophytes, their functions and ecological roles have not yet been determined [62].…”

“…Although first reported over one hundred years ago as 'mycelium radicus astrovirens' (MRA) [147,148], their global diversity and functional roles are still largely unknown [62,92,107]. Studies have shown that the composition of root endophytes in the same host plants in different forest sites are restricted to a few fungal lineages [105,106,149,150]. As previously mentioned, the main observed root endophytes belong to the group dark septate endophytes (DSE).…”

“…Root endophytes have more restrictive living environments compared to other tissue regions. In boreal forests, they often co-habit with ectomycorrhizal (ECM) fungi in l the root tips of trees [106,151,152]. It has been estimated that in forest ecosystems, endophytic DSE fungi root colonization could be more abundant than mycorrhizas [62,153].…”

Ectomycorrhizal Community on Norway Spruce Seedlings Following Bark Beetle Infestation

“…Probably Phialocephala fortinii and Meliniomyces variabilis, which increased their abundance in K2 compared to K1 and REF, are such species. P. fortinii is commonly treated as an endophyte but it was also found to create ectomycorrhizae with Scots pine [39], similarly as root-associated M. variabilis, which was found to simultaneously colonize Scots pine and Vaccinium [40,41]. The ericaceous shrubs may then serve as a source of fungal inoculum enabling the colonization of spruce seedlings in K2 where the mature forest was destroyed and true ECM fungi decreased their diversity and abundance [20].…”