Molecular and biological characterization of a trackable Illinois isolate of Barley yellow dwarf virus-PAV

In consecutive annual statewide surveys of the incidence of Barley yellow d warf viruses (BYDVs) in Illinois wheat and oat fields, 27 BYDV-PAV-like iso lates were identified. Using polymerase chain reaction (PCR), the coat prot ein regions of all 27 isolates were analyzed for restriction fragment lengt h polymorphisms. The PCR products of two isolates, one from each year, had restriction fragment profiles after digestion with HaeIII that differed fro m the other isolates. The nucleotide sequences of the coat protein regions of a laboratory isolate, BYDV-PAV-IL (PAV-IL), two of the isolates with the common restriction profile, and the two isolates with polymorphic profiles were more than 98% identical. The relatively rare isolate identified durin g the first year was designated BYDV-PAV-DK1 (PAV-DK1) and further characte rized biologically. PAV-DK1 and PAV-IL did not differ significantly in symp tom expression, but did differ significantly in rates of transmission by tw o of the three biotypes of Rhopalosiphum padi examined. Since PAV-DK1 does not occur in high levels in the state of Illinois, and its PCR products hav e a unique restriction enzyme profile, it has the potential to be used as a traceable isolate in field epidemiological experiments.