Fantastic Antagonists and Where to Find Them: The Global Distribution of Nematode-Antagonistic Fungi

Abstract

Plant-parasitic nematodes can be suppressed by antagonistic members of the local soil microbiome. Compared to bacterial antagonists, considerably more attention has been paid to nematode-suppressing fungi. However, little is known about their global distribution. As their biogeography matters from both a fundamental and an applied perspective, we set out to mine the GlobalFungi database. After filtering on sample type, biome relevance and sequencing depth, we retained approximately 28,000 samples from 484 studies. An overview of fungal nematode antagonists was generated, and subsequent analyses revealed that 82.6% of the soil samples comprised [≥]1 nematode antagonist. Most of these antagonists are not obligatory nematode parasites; they switch between trophic lifestyles including saprophytism. Nematode antagonists are frequently found across most biomes; the detection probability was highest in croplands (88% of samples), woodlands (82%), and grasslands (76%). Most of the common nematode antagonists are present on all continents and across multiple climate zones underlining their enormous ecological flexibility. With one exception, the most frequently detected antagonistic fungi belonged to the fungal order Hypocreales whose members are known to parasitize insects and fungi as well. Analysis of the impact of temperature and precipitation on common antagonists in croplands revealed mostly non-linear responses. Among a selection of six soil properties, pH was the most informative predictor for the abundance of antagonists in croplands. Insights into the prevalence and the distribution of nematode antagonists at a global scale contribute to the exploration of the nematode-suppressive potential, which appears to be more common and widespread than often assumed.