Verticillium albo-atrum partitivirus 1 Is a highly prevalent and stably maintained cryptic virus of hop-associated Verticillium nonalfalfaeMiljanić, Vanja (Avtor) Jakše, Jernej (Avtor) Radišek, Sebastjan (Avtor) Stajič, Ester (Avtor) Štajner, Nataša (Avtor) hopmycovirusVaaPV1Verticillium wiltThe soilborne plant-pathogenic fungus Verticillium nonalfalfae causes Verticillium wilt in hop. Infections caused by its highly virulent (lethal) pathotype can lead to the development of a severe level of disease that poses a major threat to hop production. In this study, we investigated the occurrence of mycoviruses in V. nonalfalfae isolates representing different geographical regions and virulence groups using double-stranded RNA isolation and high-throughput sequencing. Notably, Verticillium albo-atrum partitivirus 1 (VaaPV1) was detected in 46 of 90 isolates (51.1%), including both lethal and mild pathotypes. Thirty isolates were sequenced, revealing low genetic divergence, with nucleotide identities of 93.9%–100% for RdRp and 94.5%–100% for CP. The low dN/dS ratio of the RdRp gene (0.119) further indicated strong purifying selection. VaaPV1 was efficiently maintained during fungal growth: hyphal tipping failed to eliminate the virus from any of 70 regenerated cultures, while only 13 of 73 cultures regenerated from protoplasts were virus-free. Furthermore, VaaPV1 was transmitted horizontally through hyphal anastomosis from all tested donor isolates. Comparisons between infected and isogenic virus-free isolates revealed no significant differences in fungal growth or virulence on hop, indicating that VaaPV1 establishes a cryptic infection without detectable phenotypic effects under the conditions tested. Overall, our findings demonstrate that VaaPV1 is highly prevalent, genetically conserved and stably maintained in hop-associated V. nonalfalfae, providing a baseline for future studies of the ecological and biological significance of mycovirus infections in this vascular wilt pathogen.20262026-10-30 10:55:54Članek v reviji190604sl