ELECTROPHORETIC DISTINCTION BETWEEN THE PEACH-POTATO APHID, MYZUS-PERSICAE, AND THE TOBACCO APHID, M-NICOTIANAE (HOMOPTERA, APHIDIDAE)

The electrophoretic mobility of the enzyme glutamate oxaloacetate transaminase (GOT) on cellulose acetate plates was compared among sibling species of the Myzus persicae (Sulzer) group (M. persicae, M. nicotianae Blackman, M. antirrhinii (Macchiati)). M. persicae itself is monomorphic for GOT-1 (genotype ff), whereas European populations of M. nicotianae are polymorphic for this enzyme, with two forms of slightly different mobility (alleles s, f). In the samples of M. nicotianae examined, M. persicae-like ff genotypes were rare and heterozygotes (sf) were in large excess, even in samples from Greece where M. nicotianae has a regular holocycle (i.e., annual sexual reproduction). In North America, where M. nicotianae is probably entirely anholocyclic, samples of both red and green colour morphs of this species were found to be heterozygous for GOT-1. The enzyme difference can thus provide a means of distinguishing most individual specimens, including trapped alatae, of M. persicae and M. nicotianae. The anholocyclic taxon M. antirrhinii appears to be a fixed heterozygote for GOT-1 and thus resembles most M. nicotianae, but can be distinguished electrophoretically from both M. persicae and M. nicotianae by its distinctive pattern of esterases.