Arbuscular mycorrhizal fungal hyphae enhance transport of the allelochemical juglone in the field

• Arbuscular mycorrhiza may mediate transport of allelochemicals.
• Juglans regia material (containing juglone) effectivity is enhanced in the presence of AM hyphae.
• Garden experiments add to body of evidence for allelochemical transport via AM fungi.
• Rotated/static core arrays allowed studying effects of intact mycelia.

Allelopathy is a biological phenomenon where plants have harmful effects on growth of surrounding plants through the production of chemical substances. Here we focus on allelochemical processes which operate belowground, can influence plant interactions and therefore potentially affect plant community structure. Soil hyphae of arbuscular mycorrhizal fungi (AMF) may enhance transport processes in the soil matrix by providing direct connections between plants facilitating infochemical exchange.In a two-component field study we showed that soil hyphae likely play a crucial role in movement of allelochemicals in natural soils and greatly expand bioactive zones by providing effective transport pathways for chemical compounds. First, we tested the effects of Juglans regia leaf litter extract addition in intact or disrupted hyphal networks and simultaneously determined growth reducing effects on sensitive Lycopersicon lycopersicum plants. Second, we analyzed the effect of juglone on tomato by directly adding leaf litter. In both approaches we found an increase of juglone transport if a hyphal network was present, resulting in reduced growth of target plants.Our results, together with previous work, add to the body of evidence for hyphae of soil fungi playing an important role in the transfer of allelochemicals and effectively acting as transport highways in the field. We suggest that hyphal connections, mostly formed by AMF, increase the effectiveness of allelochemicals in natural systems and can play a crucial role in chemical interaction processes in the soil.