Mutations in zucchini yellow mosaic virus helper component protein associated with loss of aphid transmissibility

Zucchini yellow mosaic virus (ZYMV) is a potyvirus transmitted by aphids in a non-persistent manner. Isolates having partially or totally lost their ability to be transmitted by aphids have been isolated and found to be affected in their helper component activities. We have sequenced the helper component coding region of poorly aphid-transmissible (PAT) variants of two strains of ZYMV, E15 and R5A. Mutations have been identified at the nucleotide level leading to two amino acid changes in the E15 PAT variant helper component and to one amino acid change located in the cysteine-rich region (well-conserved among potyviruses) in R5A PAT variant helper component. The mutation in the R5A variant changes the same amino acid as the one identified in potato virus C, a non-transmissible strain of potato virus Y.