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

Arbuscular mycorrhizal fungi (AMF) build symbiotic relationships with over 80 % of land plants, including many invasive species. They typically benefit their host plants by promoting soil nutrient mobilization and absorption. Invasive plants often have higher rates of mycorrhizal colonization than native plants yet the reason for this is little understood. One hypothesis suggests that invasive species can alter the AMF community and receive greater benefits compared to co-occurring native plants. This would promote their invasion by increasing survival, growth rate and/or competitiveness. Alteration of the AMF community is likely facilitated by the exudation of secondary compounds from the roots. However, there have been no investigations of the regulation of AMF by secondary chemicals in invasive plants.

In a new study published in AoBP, Pei et al. investigated AMF colonization in populations of the Chinese tallow tree (Triadica sebifera). A deciduous tree native to China, T. sebifera was introduced to the USA in the late 18^th century where it has become invasive. The authors collected seeds of T. sebifera from 12 populations in southern China (native populations) and 10 populations across the south-eastern USA (invasive populations). They grew them in a common garden experiment to test the hypothesis that higher levels of root flavonoids are related to higher AMF colonization in introduced populations. The authors confirmed that AMF colonization rate was higher in introduced populations compared to native populations. Roots of plants from introduced populations also had higher levels of flavonoids and the concentrations of flavonoids in the roots was positively correlated with AMF colonization. Furthermore, AMF colonization was positively correlated with plant biomass. These findings suggest that higher root flavonoids in plants from introduced populations may promote AMF spore germination and/or attract hyphae to the roots, which subsequently increase plant growth. The authors hope that their results will aid in predicting and managing plant invasions in addition to providing important insights into the chemical mechanism of AMF–plant interactions.