Detection of barley yellow dwarf virus in aphids by serologically specific electron microscopy

A procedure employing serologically specific electron microscopy (SSEM) which consistently detected barley yellow dwarf virus (BYDV) in single aphids was developed. Using an antiserum against the Sitobion avenae (SA)-specific variant of BYDV, the virus was detected in aphids after 1 day of acquisition feeding and up to 9 days after removal from the virus source plant. The method was equally effective with alate or apterous aphids. SSEM scores of single aphids for presence of virus showed good agreement with virus transmission by aphids. In addition to the SA-specific variant, the nonspecific and Schizaphis graminum specific variants of the virus were also detected in their vectors Rhopalosiphum padi and S. graminum, respectively, using the antiserum to SA-specific variant. The SA-specific variant was also detected in aphids considered "nonvectors" (R. padi, R. maidis, and S. graminum) when fed on this variant. Application of the procedure for determining the proportion of viruliferous aphids in a population are discussed.