Desert rose (Adenium obesum (Forssk.) Roem. & Schult, family Apocynaceae) is native to southeastern Africa, and is a perennial potted ornamental with colorful flowers that are popular in Taiwan. Symptoms of mosaic and chlorotic ringspots and line patterns on leaves were observed in July 2010, on all eight plants in a private garden in Potzu, Chiayi, Taiwan. Spherical virus particles with a diameter of approximately 28 nm were observed in crude sap prepared from symptomatic leaves. Virus culture was established by successive local lesion isolation in Chenopodium quinoa and was maintained in the systemic host Nicotiana tabacum van Hicks. The virus was mechanically transmissible to indicator plants and induced symptoms similar to those incited by Cucumber mosaic virus (CMV). Observed symptoms included local lesions on inoculated leaves of C. amaranticolor and systemic mosaic in Cucumis sativus, Lycopersicon esculentum, N. benthamiana, N. glutinosa, and N. rustica. On N. tabacum, necrotic ringspots developed on inoculated leaves followed by systemic mosaic. Serological tests using ELISA assays and western blotting indicated that the virus reacted positively to a rabbit antiserum prepared to CMV (4). Amplicons of an expected size (1.1 kb) were obtained in reverse transcription-PCR with primers specific to the 3′-half of CMV RNA 3 (3) using total RNA extracted from infected desert rose and N. tabacum. The amplified cDNA fragment was cloned and sequenced (GenBank Accession No. AB667971). Nucleotide sequences of the coat protein open reading frame (CP ORF) (657 nt) had 92 to 96% and 76 to 77% sequence identity to those of CMV in subgroups I (GenBank Accession Nos. NC_001440, D00385, M57602, D28780, and AB008777) and II (GenBank Accession Nos. L15336, AF127976, AF198103, and M21464), respectively. Desert roses infected by Tomato spotted wilt virus (TSWV) (1) and CMV (2) have been reported previously. In spite of the plants showing mosaic symptoms similar to that caused by CMV (2) and chlorotic ringspots and line patterns caused by TSWV (1), only CMV was detected in and isolated from these infected desert roses. However, the possibility of mixed infection of CMV and other viruses were not excluded in this research. To our knowledge, this is the first report of CMV infection in desert rose plants occurring in Taiwan.
References: (1) S. Adkins and C. A. Baker. Plant Dis. 89:526, 2005. (2) C. A. Baker et al. Plant Dis. 87:1007, 2003. (3) Y. K. Chen et al. Arch. Virol. 146:1631, 2001. (4) Y. K. Chen and C. C. Yang. Plant Dis. 89:529, 2005.