Resolving the mycorrhizal status of important northern hemisphere trees

Abstract

Aims Knowledge about mycorrhizal associations is important for understanding mineral nutrition, stress tolerance and regeneration dynamics of trees. Here we address the mycorrhizal status of 940 species of important trees growing in ecosystems or cultivated in temperate regions of the Northern Hemisphere by resolving conflicting mycorrhizal trait information. Results Using 3800 observations from the FungalRoot database, we show that mycorrhizal status is highly consistent within species, genera and most families. Most contradictory mycorrhizal designations result from putative diagnosis errors, such as reported ectomycorrhizas EcM) in otherwise arbuscular mycorrhizal (AM) trees (10% of records). Furthermore, the most commonly studied species are more likely to have incorrect designations in databases due to accumulation of errors. Here we provide a definitive mycorrhizal status based on careful evaluation of records, with additional support from detailed anatomical observations and physiological data. We also identify common causes for errors, such as complex root anatomy in the Cupressaceae and Rosaceae. We also present detailed microscopic images of root structural features in trees with EcM or AM associations. Most AM roots have a suberised exodermis, which forms a permeability barrier around plant-fungus interfaces in the cortex and also protects roots from unwanted fungi. EcM short roots also have highly specialised anatomical features. Conclusions Tree root atatomical features demonstrate convergent evolution that is presumably linked to more efficient and specific mycorrhiza formation. We recommend that future metastudies use corrected databases and new errors be avoided by using appropriate methodology and consistent definitions of association types.

Actinorhizal plants of Turkey: formation of nodules, cluster roots and ectomycorrhizal roots

“…In contrast, ectomycorrhizal roots were present in abundance in all cases. These were short, thick, mostly unbranched roots, growing perpendicular to the main root often with some terminal swelling (Figure 1i) consistent with range in ectomycorrhizal root morphology described by Brundrett and Tedersoo (2020). This not only contrasted with their lack of nodules and rare cluster roots in this species, it also contrasted with the low numbers of ectomycorrhizal roots found on C. cunninghamiana, the only other test species to have evident ectomycorrhizal roots.…”

Mixing tree species associated with arbuscular or ectotrophic mycorrhizae reveals dual mycorrhization and interactive effects on the fungal partners

“…As we had to process 120 root samples, we were unable to prepare thin cross sections for all roots. Thus, the unequivoval identification of a Hartig net as another key characteristic of EM trees (Brundrett & Tedersoo, 2020) was not possible in all cases.…”

“…Mycorrhizae can either be studied morphologically (e.g., Baltruschat et al., 2019; Brundrett & Tedersoo, 2020; Kottke & Oberwinkler, 1986; Rumberger et al., 2004) or by meta‐barcoding (e.g., Francioli et al., 2016). Both approaches have advantages and disadvantages.…”

Biological Flora of the British Isles: Crataegus monogyna

“…Scutellospora armeniaca Błaszkowski was reported as a fungal partner of arbuscular mycorrhiza with C. monogyna in Poland (Błaszkowski, 1992). Recently Brundrett and Tedersoo (2019, 2020) have questioned the mycorrhizal research conducted over 50 years ago for misinterpretation and consider that the genus Crataegus forms arbuscular mycorrhiza only (see also Thomas et al., 2021).…”