Exploration of mycoviruses for biological control of the devastating phytopathogenic fungus Verticillium nonalfalfae

Plants are constantly threatened by pests and pathogens. The problem is getting worse due to global warming and the accompanying climate changes. Hop (Humulus lupulus L.), valued by the brewing industry and for pharmaceutical purposes, is an important economic crop for Slovenia (one of the largest hop producers in Europe). Among fungal diseases, Verticillium nonalfalfae, a soilborne pathogen, is a major problem that can lead to destruction of the entire hop plantation (Keyworth, 1942; Radišek et al., 2006). Currently, there are no effective and environmentally safe control measures available to successfully limit the infection. Therefore, finding an innovative, alternative methods for plant protection is crucial. Some mycoviruses in plant pathogenic fungi can reduce or stop the ability of their fungal hosts to cause disease in plants (Ghabrial and Suzuki, 2009; Kyrychenko et al., 2018; Kotta-Loizou, 2021). This phenomenon is known as hypovirulence or mycovirus-mediated attenuation and it has great potential for sustainable biological control (virocontrol). To date, no studies have been conducted on mycoviruses infecting V. nonalfalfae. The objectives of the proposed postdoctoral research project are to determine the mycovirome of V. nonalfalfae isolates with diverse pathogenicity range (hypovirulent and highly virulent), maintained in the culture collection of the Slovenian Institute for Hop Research and Brewing Žalec, Slovenia, which will expand our knowledge about viruses, and to determine their potential for biological control of Verticillium wilt disease (curing hypovirulent isolates, investigating transmission efficiency, pathogenicity on hops).