High-Throughput Resequencing of Bactrocera cucurbitae for the Identification of the Gene Causing the Sexually Dimorphic Pupal Color Morph White Pupae

The melon fly Bactrocera cucurbitae (Coquillette), is a destructive agricultural pest and is among one of the many species that is the target of expensive population eradication and suppression efforts within state and federal departments of agriculture. Area-wide integrated pest management programs control some species such as the Mediterranean fruit fly and the Mexican fruit fly through the release of sterile males known as the sterile insect technique (SIT). This method is not currently employed for B. cucurbitae in the United States though a genetic sexing strain (GSS) with a sexually dimorphic pupal color morph that can be used for mass-rearing and release does exist for the melon fly. In the advent of its release, a diagnostic tool will be necessary to differentiate between wild and SIT melon fly to prevent unnecessary and costly quarantines. The purpose of this project was to identify SNP loci tightly linked to the causative mutation of the genetic sexing trait white pupae (wp) in the genetic sexing strain of B. cucurbitae. To do so, a QTL map was generated using a mapping population and SNPs obtained through double-digest restriction associated DNA sequencing (ddRAD-seq). Primers were then designed which flank the most tightly linked SNPs as well as non-linked loci which demonstrated a tight association to the GSS colony and targets were successful in differentiating between GSS colony and wild flies. Tightly linked loci were further interrogated using low-coverage resequencing to identify the putative genes governing the pupal color trait. This data can used to develop a genetic assay for differentiating between recaptured sterile insect released males and wild males, will be useful for the improvement of the melon fly GSS colony, and can be used to identify an orthologous gene in other species to create novel genetic sexing strains.