Prevalence and phenology of fine root endophyte colonization across populations of Lycopodiella inundata

Abstract

Mycorrhizal fungi are critical components of terrestrial habitats and agroecosystems. Recently, Mucoromycotina fine root endophyte fungi (MucFRE) were found to engage in nutritional mutualism with Lycopodiella inundata, which belongs to one of the earliest vascular plant lineages known to associate with MucFRE. The extent to which this mutualism plays a role in resilient plant populations can only be understood by examining its occurrence rate and phenological patterns. To test for prevalence and seasonality in colonization, we examined 1305 individual L. inundata roots from 275 plants collected during spring and autumn 2019 across 11 semi-natural heathlands in Britain and the Netherlands. We quantified presence/absence of fine root endophyte (FRE) hyphae and vesicles and explored possible relationships between temperature and precipitation in the months immediately before sampling. Fine root endophyte hyphae were dominant in all of the examined heathlands, and every colonized root had FRE in both cortical cells and root hairs. However, we found significant differences in colonization between the two seasons at every site. Overall, 14% of L. inundata roots were colonized in spring (2.4% with vesicles) compared with 86% in autumn (7.6% with vesicles). Colonization levels between populations were also significantly different, correlating with temperature and precipitation, suggesting some local environments may be more conducive to root and related hyphal growth. These marked seasonal differences in host-plant colonization suggest that results about FRE from single time point collections should be carefully interpreted. Our findings are relevant to habitat restoration, species conservation plans, agricultural bioinoculation treatments, and microbial diversity studies.

Evidence for Niche Differentiation in the Environmental Responses of Co-occurring Mucoromycotinian Fine Root Endophytes and Glomeromycotinian Arbuscular Mycorrhizal Fungi

“…We chose to standardise our sampling to avoid any phenology bias among samples. A recent study on an early-divergent moss (Lycopodiella inundata) found that root colonisation by FRE was greater in autumn than in spring and authors attributed this to changes in temperature and rainfall (Kowal et al 2020). This further supports our results that FRE proliferate in wetter environments, but contradicts our results in regards to temperature.…”

“…This further supports our results that FRE proliferate in wetter environments, but contradicts our results in regards to temperature. This is likely due to the fact the temperature range used by Kowal et al (2020) was 6 to 11 °C in spring and ~3 to ~16 °C in autumn; while ours was -1 to 9.9 °C. It is possible that colonisation by FRE follows a hump-shaped patter with temperature.…”

“…1). We conducted all our sampling during winter to remove seasonality as a confounding factor (Kowal et al 2020;Ryan and Ash 1996). Briefly, intact soil cores containing T. subterraneum plants were sampled by farmers, packaged in sealed plastic 900 ml containers (30 × 20 × 5 cm; Fig.…”

Advances in understanding of mycorrhizal-like associations in bryophytes

“…in dual symbiosis (Field et al 2016, Rimington et al 2020. This situation parallels that in hornworts (Desirò et al 2013) and pteridophytes (Rimington et al 2015, with the only currently known exception being the lycophyte Lycopodiella inundata (L.) Holub which, after detailed sampling of several populations, appears to form partnerships, like Treubia and Haplomitrium, only with Mucoromycotina (Rimington et al 2015, Kowal et al 2020.…”

An evaluation for the medium-term storage and viability of root cortex tissues stained with blue ink in the assessment of arbuscular mycorrhizal fungi

“…Trypan blue stains AM fungal vesicles and spores in a similar manner, making distinguishing these difficult and risking inflated quantification of mycorrhizal associations. Sheaffer blue ink represents a non-carcinogenic alternative stain for mycorrhizal structures [7–11]. A review of staining protocols by Moukarzel et al .…”