Rapid molecular identification of Trichogramma (Hymenoptera: Trichogrammatidae) parasitizing the eggs of the European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae) in Serbia

Abstract

Abstract Background The European corn borer (ECB), Ostrinia nubilalis (Hübner, 1796) (Lepidoptera: Crambidae), is the major pest of maize (Zea mays Linnaeus, 1753) in Serbia. One potential method for managing this pest is the augmentative release of naturally occuring egg parasitoids of the genus Trichogramma. The first step in this process is accurately identifying the naturally occuring species and estimating their natural distribution and abundance. Molecular identification, based on differences in DNA sequences, has commonly been employed for the identification of Trichogramma species. A simple, quick, and accurate molecular assay is urgently required for the identification of two common Trichogramma species, associated with ECB in Serbia: T. brassicae Bezdenko, 1968 and Trichogramma evanescens Westwood, 1833. Such an assay will facilitate an expansive survey of resident populations of Trichogramma associated with ECB across agricultural growing regions of Vojvodina province. Results A species-specific multiplex PCR assay for the 2 species was developed and validated that assay using a sample of 79 parasitoid wasps reared from ECB egg masses collected from sample sites across Vojvodina province. Trichogramma brassicae was confirmed as the dominant egg parasitoid of ECB in this region, accounting for 77 of the 79 wasps (97.47%). The remaining 2 were confirmed as T. evanescens. Trichogramma brassicae was detected at all 12 sample sites, while T. evanescens was detected at only 2 plots, Mokrin and Nakovo. Conclusions The species-specific multiplex PCR assay presented herein can provide the basis of a quick, cheap, and reliable means for identifying the species of Trichogramma that parasitize ECB egg masses in Serbia. Two currently documented species, T. brassicae and T. evanescens, are readily diagnosed by the size of the PCR product they produce in the assay. Any additional species are expected to not produce a band of a diagnostic size. Such species would subsequently be identified by sequencing, which may also allow them to be promptly incorporated into a revised assay.