Aphids Influence Soil Fungal Communities in Conventional Agricultural Systems

Abstract

Arbuscular mycorrhizal fungi (AMF) form symbioses with the roots of most plant species, including cereals. AMF can increase the uptake of nutrients including nitrogen (N) and phosphorus (P), and of silicon (Si) as well as increase host resistance to various stresses. Plants can simultaneously interact with above-ground insect herbivores such as aphids, which can alter the proportion of plant roots colonized by AMF. However, it is unknown if aphids impact the structure of AMF communities colonizing plants or the extent of the extraradical mycelium produced in the soil, both of which can influence the defensive and nutritional benefit a plant derives from the symbiosis. This study investigated the effect of aphids on the plant-AMF interaction in a conventionally managed agricultural system. As plants also interact with other soil fungi, the non-AMF fungal community was also investigated. We hypothesized that aphids would depress plant growth, and reduce intraradical AMF colonization, soil fungal hyphal density and the diversity of AM and non-AM fungal communities. To test the effects of aphids, field plots of barley enclosed with insect proof cages were inoculated with Sitobion avenae or remained uninoculated. AMF specific and total fungal amplicon sequencing assessed root fungal communities 46 days after aphid addition. Aphids did not impact above-ground plant biomass, but did increase the grain N:P ratio. Whilst aphid presence had no impact on AMF intraradical colonization, soil fungal hyphal length density, or AMF community characteristics, there was a trend for the aphid treatment to increase vesicle numbers and the relative abundance of the AMF family Gigasporaceae. Contrary to expectations, the aphid treatment also increased the evenness of the total fungal community. This suggests that aphids can influence soil communities in conventional arable systems, a result that could have implications for multitrophic feedback loops between crop pests and soil organisms across the above-below-ground interface.

Plant herbivore protection by arbuscular mycorrhizas: a role for fungal diversity?

“…Metabolomic-and metagenomic-based approaches (e.g. DNA metabarcoding; € Opik et al, 2010) are valuable tools in addressing these knowledge gaps, where the inclusion of AM fungal community interactions into plant-herbivore research is likely to pave the way towards effectively managing AM fungi to enhance plant protection (Hill et al, 2018;Wilkinson et al, 2019b). Over a decade ago Wehner et al (2010) highlighted how the functional diversity of AM fungi necessitates that fungal diversity take a prominent role in research into plant pathogen protection.…”

Aphid Herbivory Drives Asymmetry in Carbon for Nutrient Exchange between Plants and an Arbuscular Mycorrhizal Fungus

“…However, in our experiment, AM fungal colonization was greater in plants that were exposed to aphids than those that were not, under both CO 2 atmospheres (Figure 3A). Using the same cytological methods, negative, neutral, and positive effects of aphid herbivory on AM colonization have been recorded across plant-AM-aphid systems [27,43], with idiosyncratic outcomes even documented between plant species within the same genus [28]. The increase in % root length colonization recorded here may have been driven by a reduction in root biomass of plants exposure to aphid herbivores (Figure 2B), with total fungal presence potentially being unchanged in roots between aphid treatments.…”

Comparative analyses of sooty mould communities from Brazil and Central Europe

“…The colour scale illustrates the dominance (%) within the sites. The dendrogram on top illustrates the similarity of the sites; the one on the left represents the similarity in the pattern of occurrence of the individual fungal OTUs and Corlett 2019; Egidi et al 2019;Epstein et al 2019;Li et al 2019;Lynikiene et al 2020;Morales-Rodriguez et al 2019;Nerva et al 2019;Qian et al 2020;Ricks and Koide 2019;Saravesi et al 2019;Wilkinson et al 2019;Würth et al 2019;Yao et al 2019;Zhang et al 2019), others strongly recommended the use of ITS1 (Mbareche et al 2020), as it had already been implemented in many studies (Beule et al 2019;Checinska Sielaff et al 2019;Del Frari et al 2019;Schiro et al 2019). Few studies are based on both ITS regions (Janakiev et al 2019).…”

“…The use of operational taxonomic units (OTUs) versus the recent use of amplicon sequence variants (ASVs) is also inconsistent. Although there are recommendations to use only ASVs (Callahan et al 2017), resulting in a reduction in the number of dominant species (Egidi et al 2019), many of the current studies are still based on OTUs (Bao et al 2019;Beng and Corlett 2019;Beule et al 2019;Checinska Sielaff et al 2019;Epstein et al 2019;Janakiev et al 2019;Lynikiene et al 2020;Morales-Rodriguez et al 2019;Nerva et al 2019;Pan et al 2019;Qian et al 2020;Ricks and Koide 2019;Saravesi et al 2019;Wilkinson et al 2019;Würth et al 2019;Yao et al 2019;Zhang et al 2019), but others rely on ASVs (Del Frari et al 2019;Egidi et al 2019;Li et al 2019), or OTUs generated from ASVs (Ezeokoli et al 2020), and even OTUs from cultivationbased Sanger sequencing are still in use (Janowsky et al 2019). With the availability of the VSEARCH tool within the QIIME2 pipeline, allowing the easy aggregation of OTUs from ASVs, the Illumina sequencing datasets in this Fig.…”