Interspecific variation in crop and weed responses to arbuscular mycorrhizal fungal community highlights opportunities for weed biocontrol

New, non-chemical weed suppression methods are needed to support multi-tactic integrated weed management (IWM) programs that reduce reliance on herbicides. One such approach is to manage arbuscular mycorrhizal (AM) fungal communities to enhance their weed biocontrol. Successful implementation will require a better understanding of AM fungi-crop-weed relationships under field conditions, especially in the face of soil disturbances imposed by agricultural practices. We examined root AM fungal communities of four weed species and one model crop species (i.e., corn) in a field experiment with contrasting tillage and cover cropping treatments in Illinois, USA. Our objectives were to quantify the impact of AM fungi on the growth of corn and weed species, to assess influences of plant species, tillage, and cover cropping on AM fungal community structure, and to characterize the co-occurrence patterns of AM fungal taxa in weed and corn roots. Our results showed that effects of AM fungal taxa on corn and weed growth varied widely depending on plant species, and several AM fungal taxa had species-specific negative effects on weeds but not on corn. In addition, plant identity was the primary factor affecting root AM fungal community structure and co-occurrence patterns, whereas effects of tillage and cover cropping were relatively limited. We propose that AM fungal taxa that have selectively suppressive effects on weeds but not on corn are candidates for developing new strategies for weed biocontrol as part of IWM. Future approaches to weed management based on direct inoculation with AM fungal taxa or manipulation of AM fungal communities through specific management practices, are promising opportunities to increase the density of weed-suppressive AM fungal taxa in agroecosystems, and our methods provide important insights for AM fungal taxa selection.