NEM-EMERGE confirms that the patchy distribution of potato cyst nematodes in a single field is driven by microbes

In a piece of research carried out by NEM-EMERGE partners at Wageningen University and Hilbrands Laboratorium reveals that soil microbial communities underlie the local suppression of potato cyst nematodes. In the same region, multiple arable fields with an unexplained patchy distribution of potato cyst nematodes were examined, and – to our surprise – the composition of the suppressive microbial communities was remarkably disparate. These results have been published as an open-access paper in Environmental microbiology, in which the authors detail the work carried out to reach these findings.

Disease suppressiveness is a complex phenomenon that is assumed to result from the actions of local microbial antagonists, often bacteria or fungi that use plant-parasitic nematodes as a food source. However, “our limited understanding of the underlying biological processes currently hampers the broader adoption of this approach as a pathogen management strategy”, researchers state in the article.

Studying these microbiomes is challenging, especially when comparing fields that differ in location, soil type, or farming practices. The ideal situation is a field that looks uniform but shows unexpected patchy outbreaks of a soil-borne disease, even though the disease was expected to be widespread based on cropping and field management history. A patchy pathogen distribution may be due to subtle differences in soil conditions or recent pathogen introduction, but it could also reflect local differences in soil microbiomes. This is exactly the approach the NEM-EMERGE partners adopted to investigate soil microbiome-based suppression of potato cyst nematodes, a major threat to global potato production.

They selected four apparently homogeneous potato fields with an unexplained non-homogeneous potato cyst nematode distribution, and made experiments to see, first, whether this patchy potato cyst nematode distribution had a biotic origin, and then, to assess whether the absence of potato cyst nematodes was associated with the presence of nematode antagonists. DNA analysis of the microbial community in the potato rhizosphere (the zone of soil surrounding a plant root, where the root and soil interact) revealed contrasts in the microbial community composition between disease-suppressive and disease-favouring patches. Elevated abundances of fungal (e.g., Metacordyceps chlamydosporia) and bacterial (e.g., Pseudomonas fluorescens) nematode antagonists were positively associated with potato cyst nematode suppressive patches. 

Researchers stress the need for further research to pinpoint the cause of this localised disease suppression, as such insights would advance our understanding of the manipulability and controllability of disease suppressive soils. Indeed, confirmation of the occurrence of potato cyst nematode suppressive soils in Europe encourages further efforts to exploit this potential as a new strategy to durably manage this notorious plant pathogen.