First Report of Soilborne Wheat Mosaic Virus in the United Kingdom.

In April 1999, severe soilborne wheat mosaic virus (SBWMV) symptoms were observed in five fields of winter wheat (Triticum aestivum, cvs. Consort, Equinox, and Savannah) on one farm in Wiltshire, UK. Affected plants were markedly stunted and had a pale mosaic on their leaf sheaths that developed into bright yellow, parallel streaks on the leaves as they unfolded. Symptomatic plants were found in discrete, elliptical patches ranging in size from a few square meters to nearly a hectare. During May and June, symptoms became less marked as temperatures increased and were restricted to lower leaves. SBWMV was positively identified in all five fields (60 to 170 plants per field) by double (W. Huth, BBA-Braunschweig, Germany; Sanofi Phyto-Diagnostics, Paris) and triple (T. Wilson, SCRI, Dundee, UK) antibody sandwich enzyme-linked immunosorbent assay and by reversetranscription polymerase chain reaction (2). Identification was confirmed by immunoelectron microscopy, including protein-A gold labeling, which revealed bipartite, rod-shaped particles typical of SBWMV. Neither wheat spindle streak mosaic virus nor barley yellow dwarf virus was detected in the field samples, nor was SBWMV detected in any other field subsequently sampled, despite a survey of the surrounding area. Wheat is the most important economic crop in the United Kingdom (≈1.9 million hectares are grown annually, yielding ≈16 million tonnes), but its position is threatened by the economic impact of SBWMV, which has decreased yields by up to 50% in the United States (1). References: (1) T. A. Kucharek and J. H. Walker. Plant Dis. Rep. 58:763, 1974. (2) R. E. Pennington et al. Plant Dis. 77:1202, 1993.