DIVERSITY AMONG ISOLATES WITHIN THE PAV SEROTYPE OF BARLEY YELLOW DWARF VIRUS

Several barley yellow dwarf virus (BYDV) isolates collected from virul iferous aphids in upstate New York were identified as PAV serotypes, b ased 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 antib ody in enzyme-linked immunosorbent assay (ELISA) and by restriction fr agment length polymorphisms of polymerase chain reaction-amplified vir al sequences. The capsid protein amino acid sequence of one of these f our 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 t wo aphid species, Rhopalosiphum padi and Sitobion avenae, was not sign ificantly 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.