Inoculation with arbuscular mycorrhizal fungi does not confer tolerance of pasture legumes to per- and poly-fluoroalkyl substance-contaminated soil.

Abstract

Environmental contamination due to per- and poly-fluoroalkyl substances (PFAS) is a growing concern globally, as they do not easily degrade and their toxicity causes chronic health issues in humans. When present in water and soil, PFAS bioaccumulate in crops and pastures, and are subsequently taken up by livestock and humans. This study examined how arbuscular mycorrhizal (AM) fungi interact with PFAS in soil, and the subsequent effects on the growth of three pasture legume crops (Medicago truncatula, Medicago sativa and Trifolium subterraneum). To do this, we used a sterilised soil spiked with PFAS, and soil collected from a PFAS-contaminated site, and inoculated soils with the AM fungus Rhizophagus irregularis. The pasture legume species grown in these experiments were highly sensitive to the presence of PFAS in the soil, with only the M. truncatula variety Parabinga displaying tolerance. Inoculation with AM fungi greatly increased plant biomass, but did not confer tolerance of the host plant to PFAS contamination. PFAS contamination did not suppress AM fungi colonisation of the roots; in some cases, colonisation was stimulated by PFAS. PFAS contamination of agricultural soils will likely reduce the growth and yield of pasture legume crops, and AM fungi will likely be unable to buffer the negative effects.