Development of an Environmental DNA Assay for Prohibited Matter Weed Amazon Frogbit (Limnobium laevigatum)

Abstract

Environmental DNA (eDNA) is widely used for detecting target species, including monitoring endangered species and detecting the presence of invasive species. Detecting targeted species using the eDNA approach is typically carried out with species-specific qPCR assays. Amazon frogbit (Limnobium laevigatum) is classified as a State-Prohibited Matter Weed in NSW, Australia. It is a fast-growing perennial aquatic weed that outcompetes native aquatic plants, leading to a reduction in the habitats of aquatic animals. Early detection is crucial for the effective management of this species. In this study, we developed a qPCR assay for L. laevigatum based on the rpoB gene sequence. This assay was validated against 25 non-target aquatic and terrestrial species. It was found to be species-specific, with the positive signal exclusively detected in L. laevigatum. The assay was highly sensitive with the modelled detection limits of 3.66 copies of DNA/µL. Furthermore, our assay was validated using environmental samples collected from field sites with and without the presence of L. laevigatum. Our assay is an effective tool for targeted eDNA detection of L. laevigatum, which will enhance efforts to monitor and control this invasive aquatic weed.