Benefits of arbuscular mycorrhizal fungi in reducing organic contaminant residues in crops: Implications for cleaner agricultural production

Arbuscular mycorrhizal (AM) fungi (AMF) can not only improve soil and plant health, but also alter the accumulation of contaminants in plants. Here, the effects of AMF on the contents of organic contaminants and the underlying mechanisms are summarized. Data show that AMF widely occur in sites contaminated with organic chemicals. In most cases, AMF improve plant tolerance to organic contaminants and enhance crop growth, leading to increased biomass of the crops. Overall, AMF decrease organic contaminant residues in crop shoots, but often cause increased accumulation of contaminants, especially persistent organic pollutants (POPs), in crop roots. The benefits and mechanisms behind AMF's role in ameliorating organic contaminant residues in crops can be summarized as follows: (1) increased biomass via improved mineral nutrition and water availability; (2) alleviation of oxidative stress induced by contaminants; (3) enhanced activities of contaminant degradation-related enzymes; (4) accumulation and sequestration of contaminants by AMF structures; (5) glomalin-related soil protein (GRSP)-triggered changes in bioavailability of contaminants; (6) stimulation of contaminant-degrading microorganisms in soil; (7) improved soil structure; and (8) reduced pesticide application via enhanced crop resistance to pathogens and improved competition with weeds. Finally, future challenges and perspectives regarding AMF's contribution to crop safety are proposed.