Characterization of a virus infecting Citrus volkameriana with citrus leprosis-like symptoms

A Citrus volkameriana tree displaying symptoms similar to citrus leprosis on its leaves and bark was found in Hawaii. Citrus leprosis virus C (CiLV-C)-specific detection assays, however, were negative for all tissues tested. Short, bacilliform virus-like particles were observed by transmission electron microscopy in the cytoplasm of symptomatic leaves but not in healthy controls. Double-stranded (ds) RNAs ≈8 and 3 kbp in size were present in symptomatic leaf tissue but not in healthy controls. Excluding poly(A) tails, the largest molecule, RNA1, was 8,354 bp in length. The ≈3 kbp dsRNA band was found to be composed of two distinct molecules, RNA2 and RNA3, which were 3,169 and 3,113 bp, respectively. Phylogenetic analyses indicated that the RNA-dependent RNA polymerase (RdRp) domain located in RNA1 was most closely related to the RdRp domain of CiLV-C. A reverse-transcription polymerase chain reaction assay developed for the detection of this virus was used to screen nearby citrus trees as well as Hibiscus arnottianus plants with symptoms of hibiscus green spot, a disease associated with infection by Hibiscus green spot virus (HGSV). All nearby citrus trees tested negative with the assay; however, symptomatic H. arnottianus plants were positive. All three RNAs were present in symptomatic H. arnottianus and were >98% identical to the RNAs isolated from C. volkameriana. We contend that the virus described in this study is HGSV, and propose that it be the type member of a new virus genus, Higrevirus.