Cytogenetic characterization of the holocentric chromosomes in the aphids Myzus varians and Myzus cerasi

Cytogenetic investigations on the holocentric chromosomes of Myzus varians and Myzus cerasi have been carried out using silver staining and C-banding followed by chromomycin A3 (CMA3) and DAPI staining in order to improve our knowledge of these pest crop species and facilitate their identification. In M. varians C-banding pattern is pecu-: liar of each chromosome pair thus allowing the identification of all homologues and the reconstruction of a reliable karyotype whereas in M. cerasi, C-positive regions result to be limited to both the telomeric regions of the X chromosomes. In both species, silver staining localizes rDNA genes on one telomere of each X chromosome; such telomeres are the unique brightly fluorescent C-positive regions after CMA3 staining, whereas all other heterochromatic bands result DAPI positive.