First report of Hibiscus chlorotic ringspot virus in Taiwan

Hibiscus (Hibiscus rosa-sinesis L.) is a malvaceous ornamental plant, originating from China, which is commonly grown as a hedge in Taiwan. Virus-like symptoms of chlorotic ringspots surrounded by a yellowish halo are frequently observed on the leaves of hibiscus plants throughout the island (Fig. 1). Extracts from these leaves produced chlorotic local lesions when inoculated onto the leaves of Chenopodium quinoa (Fig. 2), but did not produce any symptoms on Nicotiana benthamiana or N. clevelandii. After three successive single lesion isolations in C. quinoa, an isolate of a virus was obtained.

Transmission electron microscopy (TEM) of negatively-stained, partially-purified virions revealed the presence of numerous isometric virus particles measuring approximately 28 nm in diameter. According to the literature, two viruses with this particle morphology - Hibiscus chlorotic ringspot virus (HCRSV) and Hibiscus latent ringspot virus (HLRSV) - can induce ringspot symptoms on hibiscus. Using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), these partially purified virions, as well as symptomatic plants, tested positive for HCRSV using a polyclonal antibody (Agdia Inc., Elkhart, IN). In order to further confirm the result of serological test, two specific primers, HCRSV-F1 and HCRSV-R1 were designed according to a published sequence for HCRSV (Huang et al., 2000). Using these two primers, a cDNA fragment of the expected size (3.9-kb) was specifically amplified by RT-PCR from total RNA extracted from inoculated C. quinoa. Based on the morphology of virions and the results of the ELISA and RT-PCR tests, this virus has been identified as an isolate of HCRSV, a member of the genus Carmovirus. This is the first report of HCRSV and, to our knowledge, a carmovirus being identified in Taiwan.