Mitochondrial DNA sequence variation among geographic strains of diamondback moth (Lepidoptera: Plutellidae)

We examined genetic variation among 6 geographic strains of diamondback moth, Plutella xylostella (L.), using 365 base pairs of the mitochondrial gene encoding cytochrome oxidase I (COI). No sequence variation was detected within 5 of the 6 strains; 1 strain contained 2 haplotypes that differed by a single base substitution (0.27%). Sequence differences between strains of diamondback moth from Hawaii, the Philippines, and Pennsylvania ranged from 0 to 0.82%. With one exception, base pair substitutions among strains resulted in synonymous codons and did not alter amino acid sequence. Genetic divergence between strains of diamondback moth was not correlated with geographic distances between the sources of each strain. Variation in COI among populations of diamondback moth was similar to that found in other species of Lepidoptera and was substantially less than variation between diamondback moth and 2 undescribed Hawaiian Plutella species (5 and 10%, respectively). The sequences reported here provide benchmark data for related work, such as analysis of global patterns of resistance to Bacillus thuringiensis in diamondback moth.