Molecular characterization of a strain-specific repeated DNA sequence in the fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae).

The fall armyworm moth, Spodoptera frugiperda, is a migratory species composed of sympatric corn and rice strains. The strains are indistinguishable in morphology but can be recognized by molecular markers. We have cloned and characterized seven monomer units of a repeated DNA sequence, called FR, which is found exclusively in the genome of the rice strain individuals. The 189 bp FR units are tandemly organized in arrays longer than 30 kb. Female individuals possess over 100-fold more of the FR sequence than male individuals. The repeated sequence is not methylated at GGCC sites, and shows high sequence similarity among repeat units.