DNA Barcoding of Key Storage Pests Using Mitochondrial Cytochrome Oxidase I

Stored grain insect pests are of economic importance, and they spread rapidly through the grain trade. Hence, it is important to identify these pests accurately. Although several morphological methods exist, it is tedious and time-consuming. DNA barcoding using mitochondrial COI is an alternative approach that aids in precise species identification. In this study, 13 stored grain insect pests belonging to the order Coleoptera and Lepidoptera were collected from different storage structures in Coimbatore. A fragment of mt-COI was amplified and sequenced. Sequence analyses were carried out with BOLD (Barcode of Life Data System) and ABGD (Automatic Barcode Gap Discovery) tools. The barcoding gap analysis revealed that the inter-species genetic distance is greater than the intra-species genetic distance. The ABGD analysis for species delimitation partitioned the Coleopteran and Lepidopteran datasets into 9 and 4 putative species, respectively. The barcode gap was absent in more closely related species. However, analysis of their sequences revealed significant variations. Our results showed the ability of the mt-COI to discriminate between the species, thus provide a complementary technique for the diagnosis of stored grain insect pests.