First Report of Red Clover Vein Mosaic Carlavirus Naturally Infecting Lentil.

Lentil (Lens culinaris Medik.) is an important legume crop grown in the dryland Pacific Northwest areas of eastern Washington and Oregon, and northern Idaho. Lentil is highly susceptible to pea enation mosaic enamovirus (PEMV) and bean leafroll luteovirus (BLRV), and infection may result in severe yield losses. Recently, lentil was also found to be infected experimentally with red clover vein mosaic carlavirus (RCVMV) (1). The virus is most commonly transmitted in the Pacific Northwest by the pea aphid (Acyrthosiphon pisum Harris) in a nonpersistent manner. In 1997, cv. Brewer lentil bait plants were planted at the Vegetable Research Farm at Oregon State University to monitor incidence of PEMV and BLRV. Many of the plants developed symptoms typical of PEMV. However, other plants exhibited severe stunting, proliferation of axillary branches, and general chlorosis or death. Bait plants were harvested in August, and 204 random samples were tested for PEMV, RCVMV, BLRV, alfalfa mosaic alfamovirus (AMV), and pea streak carlavirus (PeSV) by standard enzyme-linked immunosorbent assay (ELISA) protocols. Antiserum for RCVMV was made in the Prosser lab against an isolate from chickpea collected in Washington State (1). RCVMV was detected in 76 (34%) of the 204 samples. PEMV, AMV, BLRV, and PeSV were detected in 197 (89.5%), 23 (11.3%), 2 (0.9%), and 0 (0%) of samples, respectively. Results showed that 75/76 of the samples positive for RCVMV were also coinfected with PEMV. Plants infected with RCVMV in the greenhouse also produced mild systemic mosaic symptoms in selected hosts inoculated mechanically, including pea (Pisum sativum L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), and lentil. Lentil and chickpea also showed moderate to severe stunting. Chlorotic local lesions were formed on Chenopodium amaranticolor Coste & Reyn. and C. quinoa Willd. Oligonucleotide primers were designed with sequence data obtained from the Washington isolate of RCVMV (1), and identification of the virus was verified in pea and lentil by polymerase chain reaction (PCR). Primer design of RCV34V and RCV653C targeted a 619-bp fragment located in the viral coat protein gene. Plants testing positive by ELISA yielded PCR products of the expected size when visualized on agarose gels. This is the first report of natural infection of lentil by RCVMV. Reference: (1) R. C. Larsen et al. Phytopathology 87:S56, 1997.