Early Detection and Identification of Parasitoid Wasps Trichogramma Westwood (Hymenoptera: Trichogrammatidae) in Their Host Eggs Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism

Abstract

Parasitoid wasps are invaluable agents in pest biological control. Early detection and identification of parasitoid immatures are vital in characterizing parasitoid-host interactions and for evaluating parasitism rates accurately in the field. Trichogramma is the most widely used parasitoid wasp, and several studies have been performed for its molecular identification. However, those studies were mainly focused on Trichogramma adults and rarely on immatures. Here, we report a method to detect and identify Trichogramma larvae in their host eggs. We designed a pair of Trichogramma-specific primers that amplified Trichogramma mtCOI sequences from Corcyra cephalonica (Stainton) eggs parasitized by any of eight Trichogramma species tested but not from nonparasitized eggs of four lepidopteran hosts. This PCR method reliably detected Trichogramma immatures in parasitized eggs as early as 1 h after parasitism. We further developed an RFLP (restriction fragment length polymorphism) assay using restriction enzymes SspI and VspI to differentiate eight Trichogramma species at their immature stage. Overall, we developed a sensitive and reliable PCR-RFLP method to detect and identify immature-stage Trichogramma in their lepidopteran hosts. This method shows promise for conveniently identifying Trichogramma in insectaries and accurately evaluating parasitism rates in the field.

Keywords: Trichogramma; immature; molecular identification; mtCOI; polymerase chain reaction–restriction fragment length polymorphism.