Arbuscular mycorrhizal fungi travel the world with underground crop harvest

Abstract

In recent years, the travel of potentially invasive plants, animals, and pathogens via international trading routes for fresh agricultural goods has been the subject of intensive research and risk assessment. Comparatively little is known about the potential impact of international food trade on the dispersal of symbiotic soil microorganisms, such as arbuscular mycorrhizal (AM) fungi. The present study thus assessed the AM fungal inoculum potential of internationally traded underground crop harvest. Twenty batches of tubers, corms or bulbs originating from eight different countries were sampled and used to inoculate Sorghum bicolor (L) Moench plants grown in a heat-sterilized, sandy dune soil from the United Arab Emirates (UAE). Results revealed that most of the underground crop harvest contained AM fungal propagules able to establish AM symbioses in the experimental microcosm. Though it is likely that most AM fungal propagules attached to harvest products will ultimately be eliminated in the waste or sewage stream, it is well possible that a certain portion would find their way into agricultural or natural ecosystems, e.g. via organic waste disposal or use of kitchen greywater for irrigation. Given the large volumes of underground crop harvest traded worldwide, its impact on AM fungal dispersal deserves further investigation and assessment of associated risks of adulteration of soil microbial communities. Future studies might also elucidate opportunities for the application of underground crop harvest sampling to the global study of AM fungal diversity in agricultural soils.