Plants in grasslands face numerous challenges, including competition for resources and defense against pathogens. Foliar fungi can reduce plant growth directly through disease or indirectly by forcing plants to allocate resources to defense rather than growth. When foliar fungi are excluded, plants can shift their resources from defense to growth and reproduction.
In addition, plants release substances through their roots, known as root exudates or rhizodeposition. These exudates significantly influence the microbial communities in the rhizosphere—the soil surrounding plant roots. However, the impact of excluding foliar fungi on rhizodeposition and the composition of the rhizosphere microbiome is not well understood.
To explore this, researchers conducted a six-year study using foliar fungicide treatments on plots planted with 16 species of native prairie plants. The study focused on the impact of foliar fungi exclusion on the rhizosphere microbiome of two common prairie species: the grass Andropogon gerardii and the legume Lespedeza capitata.
The study found that applying foliar fungicide increased aboveground biomass and overall plant production throughout the season. However, there were no changes in root biomass, seed production, or the diversity of the rhizosphere microbial community. Interestingly, the changes in aboveground plant production were closely linked to shifts in the rhizosphere microbial composition in plots treated with fungicide compared to untreated control plots.
These findings suggest that foliar fungi play an important role in how plants allocate resources to their roots, influencing the microbial community in the surrounding soil. Excluding these fungi appears to shift plant priorities, leading to changes in the soil microbiome.
