Clover yellow mosaic virus.

Clover yellow mosaic virus is not recommended for regulation as a quarantine pest by EPPO and is not included in the EPPO Alert List. A comprehensive pest risk analysis was performed by the UK Food and Environment Agency (FERA): https://secure.fera.defra.gov.uk/phiw/riskRegister/downloadExternalPra.cfm?id=3804.

Clover yellow mosaic virus.

Clover yellow mosaic virus is not recommended for regulation as a quarantine pest by EPPO and is not included in the EPPO Alert List. A comprehensive pest risk analysis was performed by the UK Food and Environment Agency (FERA): https://secure.fera.defra.gov.uk/phiw/riskRegister/downloadExternalPra.cfm?id=3804.

Susceptibility of ten red clover (Trifolium pratense) cultivars to six viruses after artificial inoculation

Seedlings of Trifolium pratense L. cultivars were mechanically inoculated with Czech isolates of Alfalfa mosaic virus (AMV), Clover yellow mosaic virus (ClYMV), Clover yellow vein virus (ClYVV), Red clover mottle virus (RCMV), White clover mosaic virus (WClMV), and a newly discovered member of the Cytorhabdovirus genus. WClMV infected 75.4% of clover seedlings; cv. Rezista was the most susceptible (93.3%), while cv. Fresko was the least susceptible (58.3%). RCMV infected 59.6% of plants; the most susceptible was cv. Tempus (77.6%), the least susceptible cv. Sprint (38.3%). While WClMV infected a higher number of seedlings, RCMV revealed more severe symptoms on affected plants. On the basis of ELISA and RT-PCR results, no cultivar was susceptible to mechanical inoculation with ClYMV and cytorhabdovirus. Moreover, cvs Fresko and Sprint were not susceptible to ClYVV and AMV, respectively.

A Virus Related to Clover Yellow Mosaic Virus Found East of the Mississippi River in Verbena canadensis in Florida

In September 2002, several unthrifty Verbena canadensis ‘Homestead purple’ plants were received at the Division of Plant Industry in Gainesville, FL. Symptoms included very subtle yellowing and distortion or stunting of the younger leaves, symptoms that could be overlooked as a nutritional problem. Symptomatic leaves were ground in phosphate buffer and mechanically inoculated to a variety of plants that included Antirrhinum majus, Chenopodium amaranticolor, Datura stramonium, Gomphrena globosa, Pisum sativum, Trifolium pratense, T. repens, Vicia faba, and Vigna unguiculata. These hosts showed symptoms similar to those described for infection by Clover yellow mosaic virus (ClYMV) (3). In addition, the virus systemically infected Arachis hypogaea, Catharanthus roseus, C. quinoa, Nicotiana benthamiana, and healthy seed-grown Verbena × hybrida. No symptoms were seen in inoculated Zinnia elegans, N. glutinosa, N. clevelandii, Lycopersicon esculentum, Cucumis sativus, or Capsicum annuum. However, back inoculations of Cucumis sativus to C. amaranticolor gave typical local and systemic symptoms. Microscopic examination of leaf strips of infected V. faba revealed banded inclusions typical of the genus Potexvirus (1). Reverse-transcription polymerase chain reaction (RT-PCR) using degenerate primers for the genus Potexvirus (2) produced a 750-bp product that is the expected product for the genus Potexvirus. The RT-PCR product was cloned in pGem-T easy (Promega, Madison, WI) and sequenced. BLAST ( http://www.ncbi.nlm.nih.gov/ BLAST/ ) analysis of the sequence showed an 82% identity at the nucleotide level with the RNA polymerase gene of ClYMV. Leaf extracts of the original verbena, several inoculated hosts, and a known sample of ClYMV in N. benthamiana were tested in sodium dodecyl sulfate immunodiffusion (4) against antiserum to the degraded capsid protein of ClYMV. A reaction of identity was seen with infected samples but not with samples for comparable virus-free plants. To our knowledge, this is the first time this virus has been found in the eastern United States. It is not known how or if the presence of this noninsect transmitted virus in an ornamental will affect the agricultural, forage, or ornamental industries in the east or how widely distributed Verbena sp. infected with this virus may be at this time. References: (1.) R. G. Christie and J. R. Edwardson. Fla. Agric. Exp. Stn. Monogr. 9, 1994. (2.) A. Gibbs et al. J. Virol. Methods 74:67,1998 (3.) M. J. Pratt. Can. J. Bot. 39:655. 1961. (4) D. E. Purcifull and D. L. Batchelor. Fla. Agric. Ext. Stn. Bull. 788, 1977.

Viruses of White Clover in Pastures of Pennsylvania, New York, and Vermont

Incidence of six viruses was tested in white clover from 28 rotationally grazed pastures of Pennsylvania (PA), New York (NY), and Vermont (VT). Each of 17 PA pastures was sampled fall 1994, spring 1995, fall 1995, and spring 1996, and 10 pastures were sampled fall 1996. Each of five NY and six VT pastures was sampled spring and fall 1995 and 1996. Enzyme-linked immunosorbent assays (ELISA) were conducted for red clover vein mosaic virus (RCVMV), white clover mosaic virus (WCMV), alfalfa mosaic virus (AlMV), peanut stunt virus (PSV), clover yellow mosaic virus (CYMV), and the potyvirus group (POTY). RCVMV, WCMV, AlMV, and POTY were detected in 28, 28, 27, and 25 of the 28 pastures and in 67, 32, 30, and 7% of the 3,065 samples tested, respectively. PSV occurred at low to moderate levels in 11 PA pastures. PSV was rare in NY and was not detected in VT. CYMV was never found. Incidence of each virus varied significantly among pastures. For any given virus, there was not a significant variation in incidence among sampling dates within the NY-VT samples. RCVMV, WCMV, and POTY varied among dates within PA.