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

Jill Kowal,Jordi Serra,Martin Bidartondo,Elena Arrigoni

doi:10.1007/s00572-020-00979-3

Jill Kowal, Jordi Serra + Show 2 more

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https://doi.org/10.1007/s00572-020-00979-3

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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 bio-inoculation treatments, and microbial diversity studies.

Highlights

IntroductionStrullu-Derrien et al 2014; Field et al 2015a)
Nutritional mutualistic exchange between mycorrhizal fungi and plant roots coevolved over millions of years (Pirozynski and Malloch 1975; Brundrett 2002; Bidartondo et al 2011; Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.London SW7 2AZ, UKStrullu-Derrien et al 2014; Field et al 2015a)
Lycopodiella was recently found to engage in a nutritional mutualism with Mucoromycotina fine root endophytes (MucFRE) (Hoysted et al 2019); they are not canonical ‘endophytes’, i.e. asymptomatic or cryptic in the host plant (Davis and Shaw 2008), but mycorrhizal (Rimington et al 2020)

Summary

Introduction

Strullu-Derrien et al 2014; Field et al 2015a) This interaction is fundamental to plant resilience, in stressful environments (Smith and Read 2010; Kowal et al 2016) and ecosystem function above and below ground (Hart and Klironomos 2003; Giovannetti 2008). Lycopodiella was recently found to engage in a nutritional mutualism with Mucoromycotina fine root endophytes (MucFRE) (Hoysted et al 2019); they are not canonical ‘endophytes’, i.e. asymptomatic or cryptic in the host plant (Davis and Shaw 2008), but mycorrhizal (Rimington et al 2020). MucFRE are the only mycorrhizal fungi to have been detected in Lycopodiella inundata roots (Rimington et al 2015; Hoysted et al 2019), in sharp contrast to other vascular plants where fine root endophytes (FRE) and Glomeromycotina (Glomeromycota) arbuscular mycorrhizal

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