Characterization of a resistance-breaking BaYMV isolate from Belgium

A field near Huccorgne, in the province of Liege, Belgium, sown with the winter barley cultivar Express, has been showing slight mosaic symptoms since 1990. As the symptoms were attributed to an infection by barley yellow mosaic virus, experimental plots for an evaluation of the resistance of barley breeding material were established there from 1991 onwards. Symptoms were scored by visual assessment on a range of cultivars including old French varieties, some resistant Japanese material and breeding material from the Plant Breeding Station, Gembloux. The results were compared with those obtained for the same material sown in a field infected with the common BaYMV and BaMMV isolates. The differences in the behavior of some cultivars or lines in the 2 fields were due to the emergence of a virus strain, which, at present, is limited to this particular field. The use of molecular-based detection techniques and partial sequencing have shown that the new viral agent characterized at Huccorgne is a strain of BaYMV.