Occurrence of barley yellow dwarf viruses in some common grasses (Gramineae) in south west England

The incidence and distribution of aphid transmitted barley yellow dwarf (BYD) viruses (PAV-, RPV- and MAV-like isolates) are described in 14 species of common pasture and hedgerow grasses from five localities of south-west England during 1987 and 1988. Isolates were identified by indirect 'sandwich' ELISA using the monoclonal antibodies MAC91, MAC92 and MAFF2. More infection was detected in 1987 than in 1988 but this was mainly due to a sharp decline at one site. Intensity of infection was greater in Poa annua and Lolium perenne populations than in most other species. BYD was not detected in Arrhenatherum elatius Elymus repens Agrostis canina and A. stolonifera . All three isolates of BYD were widespread. MAV was associated more with localities further north and RPV more with those further south. PAV was common only at the southern-most site. This geographical distribution was reasonably consistent in both years. Given these trends, susceptible grass species fell broadly into three groups with respect to isolate frequency, those predominently infected by RPV and MAV (seven spp.), those equally infected by all isolates (two spp.) and a single species, Poa annua , infected mainly by PAV. Some implications of these findings for the epidemiology and control of BYD viruses are briefly considered.