Design and assessment of primers to detect insect pests of Brassica crops in the gut contents of arthropod predators.
Techniques based on the polymerase chain reaction (PCR) have been shown as powerful tools for ecological studies of predator-prey interactions. Species-specific primers, which are designed to amplify target prey DNA from the gut contents of generalist predators, can potentially be used to develop highly specific and sensitive assays. We developed species-specific primers from the cytochrome oxidase subunit I (COI) gene for six insect pests of Brassica crops (Plutella xylostella, Pieris rapae, Hellula hydralis, Helicoverpa punctigera, Brevicoryne brassicae, and Myzus persicae). Specificity tests confirmed each primer pairs specifically amplifies prey DNA without cross-reactivity to predators or other non-target species, which are commonly found in the same habitats. These molecular markers also allow amplification of a very small amount of target DNA in the presence of substantially greater amounts of predator DNA. Although multiplexing of primers could potentially be used to detect the presence of multiple prey species in a single assay, the sensitivity of it compare with singleplex PCR was lower. Here we show that these primers are specific and sensitive and can be applied in ecological studies of predator-prey interactions in the field.