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 aphi ds in a non-persistent manner. Isolates having partially or totally lo st their ability to be transmitted by aphids have been isolated and fo und to be affected in their helper component activities. We have seque nced the helper component coding region of poorly aphid-transmissible (PAT) variants of two strains of ZYMV, E15 and R5A. Mutations have bee n 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.