Low mycovirus presence in soil saprotrophic fungi in Dutch sandy soils

Saprotrophic fungi play a fundamental role in soil ecosystems as primary decomposers, driving nutrient and carbon turnover on a global scale. Mycoviruses are considered widespread and can affect saprotrophic fungi by altering their properties, such as growth rate, stress resistance, and metabolite production. To advance the understanding of the prevalence and diversity of mycoviruses of soil saprotrophic fungi, we conducted parallel mycovirus screening in 28 saprotrophic fungi representing major groups of soil fungi and concomitantly explored soil metatranscriptomic data. De novo assembly of RNA-sequencing data uncovered two viruses from two fungal strains. One of these viruses, a ssRNA virus from Mucor sp., appears to represent a putative novel species. Analysis of eukaryotic RNA viruses in soil metatranscriptomes indicated that even though fungal and oomycete hosts made up 39.6 % of the classified eukaryotic viruses, there was no saprotrophic host assignment. Both methods showed that there were few mycoviruses in the Dutch sandy soils with different land uses. This led to the conclusion that mycoviruses affecting saprotrophic fungi may either be rare in these types of soils or more difficult to detect compared to other fungal groups. These results offer new insights into the ecological dynamics and viral associations of soil saprotrophic fungi, highlighting the need for broader sampling and improved approaches to assess mycovirus diversity and its potential ecological significance.