Identification of morphologically challenging Delia (Diptera: Anthomyiidae) species from field vegetable crops using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP)

Root feeding by the larvae of multiple Delia species can lead to economic loss in many agricultural crops. Field vegetables are subject to infestations by a species complex composed of Delia radicum (Linnaeus) (Diptera: Anthomyiidae), a pest in brassica crops (Brassicaceae), Delia antiqua (Meigen), believed to cause the majority of crop damage in onions, and the generalists Delia florilega (Zetterstedt), Delia platura (Meigen), and Botanophila fugax (Meigen) (Diptera: Anthomyiidae). Correct species identification is necessary to implement field management strategies, but these species are challenging to identify morphologically. We propose a polymerase chain reaction–restriction fragment length polymorphism method as a molecular tool to distinguish between five species of Delia and between two genetic lines of D. platura. The mitochondrial DNA cytochrome c oxidase subunit 1 barcode fragment is targeted, then the polymerase chain reaction product digested with four different restriction enzymes (AccI, BsrI, MlyI, and StyI). The BsrI enzyme distinguishes the two genetic lines of D. platura and D. florilega. The MlyI enzyme identifies B. fugax from the Delia species. Combining BsrI, StyI, AccI, and MlyI into double digestion reactions allows for rapid diagnostics among the species tested. Our method was validated using DNA from specimens collected in eastern Canada. This method provides tools in ecological and environmental studies where these species are of interest.