Serological identification and quantification of potato cyst nematodes from clean cysts and processed soil samples

Two monoclonal antibodies which specifically recognise each of the two species of potato cyst nematodes (PCN) and do not cross react with other species of soil nematodes, were used successfully in an immunoassay to identify and quantify PCN species using clean cysts and mixed populations. These antibodies show reactivity only towards antigens prepared from live eggs and they recognise antigens which are easily released from the nematodes. The results presented in this paper show that serological identification and quantification of PCN, not only from clean cysts but also from processed soil samples is achievable. A simple procedure to recover nematodes from soil samples and then to release nematode antigens was devised. The use of these procedures and the immunoassay for quantification of PCN was validated in tests with soil samples from Northern Portugal. The flotation method proved to be as efficient as the Fenwick Can for cyst recovery from soil samples. A significant correlation was obtained between results from immunoassay estimates and the traditional method of cyst picking and egg counting. The amount of organic matter (OM) present in the soil samples affected the sensitivity of the immunoassay but quantification of nematodes extracted from soil samples was possible with soils containing up to 14% of OM. The challenge remains to optimise the extraction procedures and the immunoassay, in practical conditions with highly organic soils containing cysts of different sizes and ages.