Response of UK winter cultivars to Soil-borne cereal mosaic and Wheat spindle streak mosaic viruses across Europe.

UK winter wheat cultivars were grown over three seasons at sites with natural inoculum sources of Soil-borne cereal mosaic virus (SBCMV) and Wheat spindle streak mosaic virus (WSSMV) located in France, Italy and the UK. Plants were assessed visually for virus symptoms and leaf extracts were tested for the presence of each virus using enzyme-linked immunosorbent assays (ELISA). Cultivars showing little or no foliar symptoms and low levels of virus in leaf tissue were classified as resistance to each virus. All the trials were taken to harvest and agronomic data collected. At the most heavily infected sites, severe symptoms of SBCMV were observed in all UK cultivars except Aardvark, Charger, Claire, Cockpit, Hereward and Xi 19. The latter cultivars exhibited either light or no symptoms and little or no SBCMV infection in leaves. Susceptible cultivars suffered severe damage, particularly at sites in France and the UK; a gross grain yield losses of ??% was estimated for the UK site. In fields with WSSMV, the virus failed to develop in Italy, but the virus was detected in the leaves of all the susceptible control cultivars at a site in France. However, no UK test cultivars tested positive for WSSMV. Multi-site analysis indicated that the presence of WSSMV did not increase the impact of SBCMV on the height, thousand grain weight or yield of UK cultivars. The wheat cultivars on test gave a similar response to SBCMV across three European countries, providing supporting evidence for the classification of all these populations as SBCMV. Possible sources of SBCMV resistance are discussed.