MOLECULAR CHARACTERIZATION OF CYCLIC AND OBLIGATE PARTHENOGENS IN THEAPHID RHOPALOSIPHUM-PADI (L)

Holocyclic clones of the aphid Rhopalosiphum padi (L.) reproduce by cy clic parthenogenesis, whereas anholocyclic individuals are obligate pa rthenogens. Mitochondrial DNA (mtDNA) and random amplified polymorphic DNA markers in R. padi as well as plasmid DNA markers of its bacteria l endosymbiont, Buchnera aphidicola, were examined to determine the ex tent of genetic divergence between clones with these differing breedin g systems. These analyses revealed that cyclically parthenogenetic lin eages possessed differing mtDNA and plasmid haplotypes than most oblig ately asexual clones. The extent of sequence divergence between these maternally inherited molecules suggests a relatively ancient origin of asexuality. Our work also identified a random amplified polymorphic D NA marker linked to the life-cycle variation in R. padi. This marker n ot only permits the rapid diagnosis of breeding system but sets the st age for studies to identify the gene(s) controlling this variation in mode of reproduction.