Current knowledge on mycoviruses associated with mycorrhizal fungi

Mycorrhizal fungi (MF) receive carbon from their plant host, colonizing the latter’s cortical cells and tissues or just around the root epidermis. Mycoviruses are viruses that infect fungi present in different taxa with members inducing cryptic, hypovirulent, or hypervirulent symptoms. They occur in different fungal taxa and hence, it is not surprising to discover the existence of viruses infecting mycorrhizal fungi. This paper examined several studies focusing on Arbuscular mycorrhizal fungi (AMF)–mycovirus symbiosis, and diversity, and presents mycovirus studies’ current status and development in this important fungal type and ecology. Despite the relative difficulty of investigating AMFs due to their obligate biotrophic nature, progress is still being made. Sixteen proposed and putative mycoviruses were infecting AMFs. Twenty-two mycoviruses from varying families and genome types are identified as infecting orchid mycorrhizal fungi. Twenty-three viruses of diverse families and 34 Partitiviruses of a single fungus are associated with ectomycorrhizal fungi. Description and characterization of viruses isolated from mycorrhizal fungi helped us grasp the great diversity of mycoviruses. With high throughput sequencing, the area of mycorrhizal virology has been gaining momentum in the past years. Extensive knowledge of mycorrhizal development and physiology can aid us in which fungal virus to use for the benefit of the host plant interest. A considerable part of mycoviruses infecting MFs remains unknown. Further research is needed to calculate the risks associated with using mycoviruses as a biocontrol against plant pathogenic and mycorrhizal fungi. Whole genome sequences are also lacking. Methodologies focusing on protoplast regeneration and hyphal anastomosis of mycorrhizal fungi are gradually being modified and tried. Finally, a closer look at the key players and mechanism of RNA silencing suppressors would shed light on the pathogenicity of mycorrhizal viruses in fungi and their associated symbionts.