Three mitovirus strains infecting a single isolate of Fusarium circinatum are the first putative members of the family Narnaviridae detected in a fungus of the genus Fusarium

Abstract

Fusarium circinatum Nirenberg & O'Donnell (teleomorph = Gibberella circinata) is the causal agent of pitch canker disease of pines. Since 2004 it has been present in Europe, particularly in northern Spain, affecting P. radiata and P. pinaster in plantations and nurseries. The disease has now also spread to other European countries, including France, Italy and Portugal. In this report, we describe three novel members of the genus Mitovirus from a Spanish isolate of F. circinatum: Fusarium circinatum mitovirus 1 (FcMV1), FcMV2-1 and FcMV2-2. Using a mitochondrial translation table, the complete 2419-bp genome of FcMV1 encodes an RNA-dependent RNA polymerase of 731 amino acids (GC-content ca 30 %). The partial genomes of FcMV2-1 and FcMV2-2 (2193 and 1973 bp, respectively) share ca 48 % RdRp sequence similarity at the aa level and might be regarded as conspecific, while FcMV1 is clearly distinct, showing 32-35 % polymerase similarity to the other strains. However, FcMV1 shared 46 % protein-level similarity with Thielaviopsis basicola mitovirus. This is the first study to report viruses in F. circinatum, as well as the first time that mitovirus genome sequences are described from Fusarium spp.