Fungal communities in wheat grain show significant co-existence patterns among species

The wheat grain mycobiome is only scarcely investigated and focus has been on seed-transmitted wheat pathogens of agricultural importance. In this study, we used next generation sequencing to study the mycobiome of Danish wheat grain samples at harvest. In total 228,421 sequences were obtained from 90 samples that were taken from locations across Denmark during three years. These sequences could be grouped into 173 non-singleton operational taxonomic units (OTUs) of which 21 OTUs, identified as belonging to genera such as Fusarium, Alternaria, Cladosporium. Phaeosphaeria and Microdochium, were identified as 'core' OTUs as they were found in all or almost all samples and accounted for almost 99 % of all sequences. The remaining OTUs were only sporadically found and only in small amounts. Cluster and factor analyses showed patterns of co-existence among the core species. Cluster analysis grouped the 21 core OTUs into three clusters: cluster 1 consisting of saprotrophs, cluster 2 consisting mainly of yeasts and saprotrophs and cluster 3 consisting of wheat pathogens. Principal component extraction showed that the Fusarium graminearum group was inversely related to OTUs of clusters 1 and 2.