Arbuscular mycorrhizal (AM) fungi can confer protection to host plants against some root pathogens,
and several mechanisms for these phenomena have been proposed. If AM fungal taxa vary in the ways
that they limit the negative effects of pathogens on host plants, additive and/or synergistic interactions
among members of diverse AM fungal assemblages and communities may result in a greater pathogen
protection than is currently predicted. However, in a review of the literature on interactions between
AM and pathogenic fungi, we found few examples that compared the effectiveness of single-