In 1994, potato samples for certification from Idaho seed fields reacted in enzyme-linked immunosorbent assay (ELISA) tests to a polyclonal potato carlavirus M (PVM) antiserum. Sample affinity to the antiserum was lower than control samples. Furthermore, ELISA-positive samples were obtained from both symptomatic as well as asymptomatic plants. A complementary DNA library was prepared using both reverse transcription-polymerase chain reaction and primers based on published PVM sequences, or oligo d(T) primed reverse transcribed sequences. The nucleotide sequence was determined for the 3′-terminus of the genome. Putative coat protein amino acid sequence was compared to published PVM and potato virus S coat protein sequences. While this new isolate is likely a strain of PVM, it is significantly different from known PVM coat protein sequences in the amino terminus region. These differences may explain the poor reactivity to other PVM antisera and suggest that it is a new strain of PVM, which we have designated PVM-ID.
A New Strain of Potato Carlavirus M