Development and use of a monoclonal antibody to detect semi‐digested proteins of the English grain aphid, Sitobion avenae, in the guts of ladybird beetle predators

Abstract

AbstractA monoclonal antibody (McAb), EGA‐4A9, was developed to detect the semi‐digested proteins of the English grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), in predatory ladybird beetles (species of the genera Adonia, Coccinella, Hippodamia, and Propylea) using the gut homogenate of Adonia variegata (Goeze) (Coleoptera: Coccinellidae) adults which had fed on S. avenae as immunogen. The McAb was selected by screening hybridoma lines for antibodies that bound with the semi‐digested aphid proteins in ladybirds. A double antibody sandwich enzyme‐linked immuno‐sorbent assay (ELISA) using ClonotypingTM System/HRP showed that it belonged to the IgG2a isotype. It did not cross‐react with any of the 21 arthropod species tested besides the ladybird beetles fed on S. avenae with an indirect ELISA. It could still detect the semi‐digested proteins in the gut of a ladybird adult, kept at 25 °C, that had ingested one aphid 6 days before. The extended antigen detection period and the high specificity of the antibody indicated that EGA‐4A9 could be used to study interactions between English grain aphids and their ladybird predators in the field. Between 28 and 72% of coccinellids collected from the field were positive for English grain aphid protein by ELISA. The percentage of McAb‐positive predatory ladybird beetles was positively correlated with the density of S. avenae in wheat fields.