A totivirus infecting the mutualistic fungal endophyte Epichloe festucae

Epichloe festucae (Ascomycota) infects the grass Festuca rubra. Infected plants may be more resistant to herbivores and obtain other benefits. The 5109 bp dsRNA genome of a virus which infects E. festucae was sequenced, and its incidence in natural populations and transmission were studied. The viral genome has characteristics of the family Totiviridae. Its two ORFs are overlapped by four nucleotides; ORFI codes a 765 amino acid putative coat protein (CP); ORF2 is in a-I frameshift with respect to ORFI, and codes a 826 amino acid RNA dependent RNA polymerase (RdRp). This virus, denominated Epichlo, festucae virus I (EfVl), is closely related to members of the genus Totivirus which infect filamentous fungi, as deduced from phylogenctic analyses of CPs and RdRps. In two natural populations of Epichloe festucae, 36.4% of the isolates were infected by EfV1. The virus was efficiently transmitted to asexual fungal spores. However, when ascospore progeny of matings between virus-free and infected strains was analyzed, it was found that the virus was not transmitted to progeny of sexual spores. (c) 2006 Elsevier B.V. All rights reserved.