Diversity among isolates within the PAV serotype of barley yellow dwarf virus

Several barley yellow dwarf virus (BYDV) isolates collected from viruliferous aphids in upstate New York were identified as PAV serotypes, based on their reaction with a polyclonal antiserum to NY-PAV. Four of six isolates examined were distinguished from the NY-PAV type isolate of BYDV by their failure to react with a PAV-specific monoclonal antibody in enzyme-linked immunosorbent assay (ELISA) and by restriction fragment length polymorphisms of polymerase chain reaction-amplified viral sequences. The capsid protein amino acid sequence of one of these four isolates, designated PAV-129, was less similar to that of NY-PAV (86.5% similar) than NY-PAV is to two other isolates, serotyped as PAV, from Indiana (98% similar) or Australia (97% similar). In biological comparisons of PAV-129 and NY-PAV, the efficiency of transmission by two aphid species, Rhopalosiphum padi and Sitobion avenae, was not significantly different; however, PAV-129 caused more severe symptoms when inoculated to a variety of oat genotypes. In addition, the growth and grain yield of 'Ogle', a spring oat considered resistant to the BYDV PAV serotype was significantly reduced when infected with PAV-129.