Genetics of Thrips palmi (Thysanoptera: Thripidae)

Melon thrips (Thrips palmi) is the principal insect pest of vegetable and ornamental plants worldwide. In addition to inflicting feeding injuries on host plants, they act as vectors of economically damaging tospoviruses. Application of insecticides and host plant resistance has proven largely ineffective in the management of T. palmi. However, increasingly, genetic knowledge is being successfully utilized to manage insect pests. A number of recent studies have enriched the genetic database of T. palmi. In this review, we report on genetics of T. palmi for species identification and to study its populations structure. For example, a DNA polymorphism analysis of global T. palmi populations has revealed the existence of 29 haplotypes. The T. palmi population can be divided into three lineages based on phylogenetic analysis. A high maximum intraspecific distance is indicative of cryptic species within T. palmi populations. Regarding climate adaptability, the upregulation of trehalose biosynthesis genes, and genes encoding several heat-shock proteins is expected to enable T. palmi thermal adaptation to both cold and hot conditions. Genetics of T. palmi has shown that resistance to conventional insecticides like cypermethrin appears to be linked to mutations in the sodium channel. On the other hand, resistance to imidacloprid appears to be a result of cytochrome P450-mediated detoxification. T. palmi genes potentially involved in tospovirus transmission are also reviewed and new molecular tools for genetic study presented. Molecular modeling and docking analyses of groundnut bud necrosis virus glycoprotein demonstrated protein-protein interactions with T. palmi vacuolar ATP synthase E subunit, cathepsin, clathrin, adaptor protein 2, and enolase. Overall, a better knowledge of T. palmi genes will assist elucidation of thrips identification, means of adaptation in diverse ecological niches, mechanisms of insecticide resistance, and transmission of plant viruses. This data will be an invaluable tool for integrated thrips management.