Occurrence of two different species of mitoviruses in the European race of Gremmeniella abietina var. abietina, both hosted by the genetically unique Spanish population

Abstract

The genetic structure of the genus Mitovirus community hosted by the European pathogenic conifer fungus Gremmeniella abietina var. abietina was investigated. Gremmeniella abietina is a species complex with a divergent mycovirus community, composed mainly of Totivirus, Partitivirus, and Mitovirus species. In this work, the total doubled-stranded (ds)RNA from 353 isolates from Canada, Finland, Spain, Switzerland, Turkey, and USA was extracted to look for the presence of a ca. 2.5 kb band typical of mitoviruses' genomes. Based on the banding data, 60 partial RNA-dependent RNA polymerase (RdRp) DNA sequences (ca. 500 bp) were amplified with reverse transcription-polymerase chain reaction (RT-PCR) and sequenced. Two distantly related mitovirus groups (species) were observed in the clustering analysis, one of them related to GMV1-1 and the other one related to a new putative species described in this study, GMV2-1. Viruses in these two clusters seemed to be subjected to purifying selection. The cluster with GMV1-1 included viruses observed in the Finnish biotype A and Spanish strains, whereas the cluster including GMV2-1 was composed of viruses of the Finnish biotype B and one from the Spanish population. Thereby, the Spanish population of G. abietina harboured mitovirus strains occurring in both biotype A and B strains, and it is the first one hosting distantly related mycoviruses of a single genus in one population of G. abietina. This may suggest that horizontal transmission of viruses could have occurred between biotype B and the Spanish population.