A study of variation in rDNA ITS regions shows that two haplotypes coexist within a single aphid genome.

We report variation in the rDNA internal transcribed spacers (ITSs) of aphid species, the first for these insects. Variation at 6 sites within ITS1 sequences of the green peach aphid, Myzus persicae, identified two haplotypes coexisting within the same individuals, indicating that molecular drive has not homogenised different copies of rDNA. During this study, we found that PCR can cause a precise 58-bp loss in the amplified copies of an ITS haplotype (type 1). This occurs in all detectable copies under routine PCR conditions, at different annealing temperatures and with Pfu and Taq polymerases. In addition, "hot-start" PCR exclusively copied a different, rare haplotype (type 2). These observations have important considerations for using PCR, as large deletions in PCR products may not reflect real deletions in the genome, and changes in PCR conditions may be needed to copy cryptic haplotypes.