Serological identification and quantification of Heterodera avenae from processed soil samples

Abstract

Monoclonal antibodies (MAbs) and polyclonal antibodies (PCs) were produced to antigens of an Australian population of cereal cyst nematode (CCN), Heterodera avenae. MAb IACR CCNj-49.2 recognised an antigen with a molecular weight of approximately 200 kDa, which was immunolocalised apparently in granules in the nematode gut. A procedure to extract CCN antigens from soil samples, under laboratory conditions was devised, and 50 g samples of soil containing 5 CCN cysts were processed by two sets of flotation techniques to recover the nematodes. Milling using Ballotini glass beads was then used to release the antigens from the CCN cysts recovered in the float. A double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) was the better ELISA format used to identify and quantify the CCN population from the processed soil samples containing up to 20% of organic matter. The threshold limit of detection was estimated by serial dilutions of the soil extracts. It was approximately equivalent to 0.5 eggs or 3.6 eggs per g of soil in a DAS-ELISA, when using respectively the PC or the MAb as the trapping antibody. The assay could be made more sensitive in soils with lower contents of organic matter.