Root flavonoids are related to enhanced AMF colonization of an invasive tree

Abstract

Arbuscular mycorrhizal fungi (AMF) are important mutualistic microbes in soil, which have capacity to form mutualistic associations with most land plants. Arbuscular mycorrhizal fungi play an important role in plant invasions and their interactions with invasive plants have received increasing attention. However, the chemical mechanisms underlying the interactions of AMF and invasive plants are still poorly understood. In this study we aim to test whether root secondary chemicals are related to enhanced AMF colonization and rapid growth in an invasive tree. We conducted a common garden experiment in China with Chinese tallow tree (Triadica sebifera) to examine the relationships among AMF colonization and secondary metabolites in roots of plants from introduced (USA) and native (China) populations. We found that AMF colonization rate was higher in introduced populations compared to native populations. Roots of plants from introduced populations had lower levels of phenolics and tannins, but higher levels of flavonoids than those of plants from native populations. Flavonoids were positively correlated with AMF colonization, and this relationship was especially strong for introduced populations. Besides, AMF colonization was positively correlated with plant biomass suggesting that higher root flavonoids and AMF colonization may impact plant performance. This suggests that higher root flavonoids in plants from introduced populations may promote AMF spore germination and/or attract hyphae to their roots, which may subsequently increase plant growth. Overall, our results support a scenario in which invasive plants enhance their AMF association and invasion success via genetic changes in their root flavonoid metabolism. These findings advance our understanding of the mechanisms underlying plant invasion success and the evolutionary interactions between plants and AMF. Understanding such mechanisms of invasive plant success is critical for predicting and managing plant invasions in addition to providing important insights into the chemical mechanism of AMF–plant interactions.

Increasing flavonoid concentrations in root exudates enhance associations between arbuscular mycorrhizal fungi and an invasive plant

“…Our previous study found higher concentrations of flavonoids but lower concentrations of tannins in roots of introduced populations of T. sebifera than in native populations [17] with quercetin and quercitrin being the main flavonoids [28,30]. In our pilot experiment, we only detected quercetin and quercitrin in root exudates but no other flavonoids.…”

“…Secondary chemicals are key root exudate components that could significantly affect AM fungal growth and colonization [17][18][19][20][21]. In particular, flavonoids, such as quercetin and quercitrin, have been reported to stimulate AM fungal spore germination and/or hyphal growth [22,23].…”

Linking Plant Secondary Metabolites and Plant Microbiomes: A Review

“…Apart from impacting legume and bacterial interactions, flavanones (such as strigolactones) can positively influence the growth of ectomycorrhizal fungi and increase the colonization of AM fungi. For example, flavanones can enhance the germination of spores of ectomycorrhizal fungi in genera Pisolithus and Suillus as well as stimulate the production of symbiotic effector protein in the mushroom Laccaria bicolor ( Garcia et al, 2015 ; Pei et al, 2020 ). In contrast, the suppression of flavonoids and phenylpropanoid pathway secretion reduced the endophytes and ectomycorrhizal colonization of the maize and poplar roots, respectively ( Mehmood et al, 2020 ).…”

Effect of Different Combinations of Phosphorus and Nitrogen Fertilization on Arbuscular Mycorrhizal Fungi and Aphids in Wheat

“…The fungal structures were stained with 0.05% Trypan blue for 24 h, after being washed in tap water five times. We then washed the Trypan blue out of the test roots and counted the hyphae at each of 300 gridline intersections on thirty 1 cm fine root segments, all from a single flowerpot, at 200 × microscope magnification [56][57][58].…”