Molecular characterization of clones of the Myzus persicae complex (Hemiptera : Aphididae) differing in their ability to transmit the potato leafrollluteovirus (PLRV)

A prerequisite to studying the specific interactions involved in the persis tent transmission of luteoviruses such as the potato leafroll virus (PLRV) is the characterization of both the virus and its vectors. A range of techn iques was used to assess genetic differentiation among 27 clones belonging to the Myzus persicae complex (M. persicae (Sulzer), M. antirrhinii (Macchi ati) and M. nicotianae Blackman) and showing different efficiencies in tran smitting PLRV isolates. All M. persicae/M. nicotianae clones belonged to on e of two karyotypes, both 2n = 12, either normal or carrying an autosomal t ranslocation (A1,3), and all M. antirrhinii clones had 13 or 14 chromosomes . Amplified esterase 4 genes were detected by PCR-REN assay in M. persicae/ M. nicotianae taxa, with gene expression being modified by methylation. Sim ilarly, amplified E4 genes were revealed in M. antirrhinii but they all sho wed unmethylated. Two allozyme and 11 microsatellite loci discriminated 10 different genotypic classes among the 27 clones. Analysis of genetic relate dness between these genotypic classes revealed that M. nicotianae clones we re very closely related to M. persicae clones, whereas the genetic differen tiation between M. antirrhinii and M. persicae was greater. The implication s of these results for the taxonomic status of these genotypes within the c omplex, and the transmission of PLRV, are discussed.