Mycoviruses in pastures and turfgrasses

Mycoviruses are a group of viruses widely present in various fungi and oomycetes, wherein they complete their life cycles. Most mycoviruses cause no symptoms in their hosts, but some can cause hypovirulence and debilitation of their hosts. Hypovirulence-related mycoviruses have been detected in some grass pathogens including Helminthosporium victoriae, Rhizoctonia solani, and Fusarium graminearum. Recently, researchers discovered a mycovirus, CThTV, which could improve heat tolerance of the host, Curvularia protuberata, in a Dichanthelium lanuginosum–Curvularia protuberata symbiosis. Grass is the fundamental source of livestock feed and plays an essential role in terrestrial ecosystems. Grassland degradation and diseases have become increasingly severe, raising concerns about serious economic losses in the livestock industry. Here, we have systematically reviewed the definition and taxonomy of mycoviruses, their effects on the host, and the research status of mycoviruses, particularly in relation to pathogenic and endophytic fungi of grasses. We aimed to clarify the diversity and functions of mycoviruses, to facilitate mycovirus research and application in the field of grass-disease prevention and resistance improvement.