Patchy Distribution of Potato Cyst Nematodes Within Single Arable Fields Reveals Local Disease Suppressiveness Mediated by Disparate Microbial Communities

Abstract

Disease suppressiveness is a complex phenomenon that is assumed to be the resultant of the actions of local microbial antagonists. Exploitation of disease suppressiveness as a tool to manage pathogens is hindered by our poor understanding of this phenomenon. Here we investigated soil microbiome-based suppression of potato cyst nematodes (PCN), and to this end, four apparently homogeneous potato fields with an unexplained non-homogeneous PCN distribution were selected. We hypothesised that this patchy PCN distribution resulted from local variation in disease suppressiveness. Under controlled greenhouse conditions, we confirmed the overall suppressiveness of these soils vis-à-vis PCN and soils were gamma-irradiated to corroborate the biotic origin of this suppression. Subsequent DNA-based analysis of the microbial community in the potato rhizosphere revealed suppressiveness-related contrasts in community composition between suppressive and conducive patches. Elevated abundances of fungal (e.g., Metacordyceps chlamydosporia) and bacterial (e.g., Pseudomonas fluorescens) nematode antagonists were positively associated with PCN suppressive patches. Distinct sets of antagonists were found to be associated with PCN suppression despite the geographical closeness of the locations under investigation. Our findings confirm the biotic origin of local PCN suppressiveness and reveal that disparate microbial communities could achieve similar outcomes.