Host Range, Purification, and Genetic Variability in Sweet potato chlorotic fleck virus

Sweet potato chlorotic fleck virus (SPCFV) has recently been classified as a putative new member of the genus Carlavirus (family Flexiviridae) on the basis of its molecular properties. In this study, SPCFV was characterized in terms of host range, physical and biological characteristics, and genetic variability. In addition to sweet potato, SPCFV infected some plant species in the families Convolvulaceae, Chenopodiaceae, and Solanaceae. Limited numbers of virus particles were observed in the assimilation parenchyma cells of infected plant tissues; some cells had a distorted and enlarged endoplasmic reticulum though without any cytoplasmic and amorphous inclusions. The normal length of SPCFV particles was determined to be approximately 800 nm. In enzyme-linked immunosorbent assays, polyclonal antibodies raised against purified SPCFV virions were able to detect the virus in infected sweet potato and indicator plant tissues. In immunoelectron microscopy, SPCFV particles were all strongly decorated when reacted with homologous antiserum. Comparison of the 3' terminal part of the genome of a range of geographically diverse isolates revealed a high level of genetic diversity. The amino acid sequence identity in the coat protein and the nucleic acid binding protein ranged from 89 to 99.7% and from 75.9 to 99.2%, respectively. Phylogenetic analysis of both proteins showed a geographically associated clustering into two genogroups.