Root Exudates Regulate Soil Fungal Community Composition and Diversity

Abstract

Plants are in constant contact with a community of soil biota that contains fungi ranging from pathogenic to symbiotic. A few studies have demonstrated a critical role of chemical communication in establishing highly specialized relationships, but the general role for root exudates in structuring the soil fungal community is poorly described. This study demonstrates that two model plant species (Arabidopsis thaliana and Medicago truncatula) are able to maintain resident soil fungal populations but unable to maintain nonresident soil fungal populations. This is mediated largely through root exudates: the effects of adding in vitro-generated root exudates to the soil fungal community were qualitatively and quantitatively similar to the results observed for plants grown in those same soils. This effect is observed for total fungal biomass, phylotype diversity, and overall community similarity to the starting community. Nonresident plants and root exudates influenced the fungal community by both positively and negatively impacting the relative abundance of individual phylotypes. A net increase in fungal biomass was observed when nonresident root exudates were added to resident plant treatments, suggesting that increases in specific carbon substrates and/or signaling compounds support an increased soil fungal population load. This study establishes root exudates as a mechanism through which a plant is able to regulate soil fungal community composition.

Rhizosphere microbiome assemblage is affected by plant development

“…The soil is described in detail in Broeckling et al (2008); soil from the same site was used in previous studies (Broeckling et al, 2008;Badri et al, , 2013a. Arabidopsis thaliana seeds were surface-sterilized with Clorox for one minute and subsequently rinsed four times with sterile distilled water.…”

“…Evidence demonstrating the close ties root exudates have on the microbial composition of the rhizosphere is mounting (Broeckling et al, 2008;Badri et al, , 2013aMicallef et al, 2009b;Chaparro et al, 2012Chaparro et al, , 2013, whereby many chemicals present in root exudates act as substrates, chemotactic or signaling molecules to orchestrate changes in microbial composition (Shaw, 1991;de Weert et al, 2002;Jain and Nainawatee, 2002;Horiuchi et al, 2005;Bais et al, 2006;Badri and Vivanco, 2009;Neal et al, 2012;Badri et al, 2013a). Recently, it was reported that the composition of Arabidopsis root exudates change following a plant developmental gradient (Chaparro et al, 2013).…”

Pythium oligandrum: an example of opportunistic success

“…Microbial diversity in the rhizosphere is linked to plant species mainly because interactions between root exudates and soil micro-organisms are highly dynamic in nature and based on coevolutionary pressures (Broeckling et al, 2008). In the past few years, only a few studies have focused on the impact of biocontrol agents (Cordier & Alabouvette, 2009;Vallance et al, 2011) on the structure and function of the rhizosphere microbiome.…”

Seasonal switchgrass ecotype contributions to soil organic carbon, deep soil microbial community composition and rhizodeposit uptake during an extreme drought

“…Some bacterial endophytes associated with switchgrass and have been shown to increase plant growth (Xia et al, 2013). Plant root exudation patterns can select different microbial communities even between plant cultivars, resulting in strikingly different microbial communities in lab settings (Broeckling et al, 2008;Gschwendtner et al, 2010). To our knowledge, this is the first field demonstration of plant-specific microbial interactions between switchgrass ecotypes.…”