First viruses infecting cockspur coral tree (Erythrina crista-galli L.): discovery of a putative novel capillovirus and a new host for the prune dwarf virus

A cockspur coral tree (Erythrina crista-galli, Fabaceae) from the collection of woody ornamentals of the Botanical Garden (Faculty of Science) in Zagreb showed conspicuous virus-like symptoms. The leaf tissue was analyzed by high throughput sequencing (HTS), revealing the presence of two viruses: prune dwarf virus (PDV, genus Ilarvirus) and an unknown virus belonging to the genus Capillovirus (family Betaflexiviridae). The complete sequence of PDV RNA3 of 2,129 nucleotides (nts) coding for the coat and movement proteins was obtained. The complete coding region spanning 6,483 nts was obtained for the capillovirus. It contained all expected open reading frames, and its maximum nucleotide identity was 42% with apple stem grooving capillovirus sequence (GenBank accession number LC143387). As this is far below the threshold for species delineation within the genus Capillovirus, we propose the name Erythrina capillovirus (ErCV) for this putatively new virus and a new virus species Capillovirus ErCV in the family Betaflexiviridae. RT-PCR confirms the presence of ErCV and PDV in symptomatic E. crista-galli, an unusual and exotic fabaceous host with no viruses recorded yet. Asymptomatic Erythrina plants were tested negative for the two viruses in RT-PCR, which, together with their presence in the symptomatic plant, suggests the capillovirus and/or PDV might play a role in eliciting observed symptoms and deserve further investigations.