Coupling scanning electron microscopy with DNA barcoding for morphological and molecular identification of thrips

The chilli thrips, Scirtothrips dorsalis Hood have been a serious problem across the globe. The small size and cryptic nature of S. dorsalis and various other thrips pests help them acquire microhabitats of a plant and in the field, often making their monitoring and the identification process difficult. The availability of inadequate specimens of these tiny creatures for identification is another limitation. Accurate identification of such pests is a fundamental requirement in development of any effective quarantine and management strategies. Thus, with the aim to obtain accurate identification of various pest species in the order Thysanoptera, a preliminary study was conducted on S. dorsalis specimens. We coupled morphological and molecular identification techniques to develop a quick, reliable and simple diagnostic method. Prior to the DNA extraction of S. dorsalis specimens, larvae and adults were subjected to traditional morphological identification using high resolution scanning electron microscopy and then gold/palladium sputter coated thrips specimens were processed for PCR assay for molecular identification. Sequence results of both mtCO1 and ITS rDNA of individual larva and adult S. dorsalis were in agreement with the taxonomic identification conducted using SEM and each result confirmed the other technique. In the past, thrips specimens had to be slide mounted for morphological identification and were destroyed or rendered unusable for DNA analysis. Our results suggest that the two techniques together could be used for the correct identification of various thrips species using a single specimen.