Expression of immunity and general condition in the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), in relation to origin and gender

In immunoecological studies, experimental effects usually explain a relatively small proportion of total variation observed in immune parameters, while the large amount of variation remains unexplained. It is crucial to be aware of such natural variation of immune parameters, which may overshadow the effects of the experiment. We examined factors responsible for variation in cellular immunity (estimated as hemocyte concentration) and general condition (estimated as fresh weight) in the Colorado potato beetle, Leptinotarsa decemlineata, originating from two neighboring potato fields, in a common garden experiment. Progeny of beetles collected from the “New” field, where potato was cultured for the first year, had significantly higher hemocyte concentration and fresh weight compared to individuals originating from the “Old” field, where potato had been cultured for several years. Furthermore, hemocyte concentration varied with respect to gender only in beetles originating from the New field, where males had a higher hemocyte concentration than females. No such sex differences were found in beetles originating from the Old field, suggesting that immune traits and general condition of insects originating from geographically close locations/populations may express different sources of variation. Therefore, generalization of immunity–life‐history trade‐offs based on one population/location should be treated with caution.     

Time-resolved fluoroimmunoassay of potato virus M with monoclonal antibodies

Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double-antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots. MAbs against PVM were used as capture antibodies and europium-labelled MAbs as conjugates in time-resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10^--⁴ with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double-label TRFIA using europium-labelled MAbs to PVM and samarium-labelled MAbs to PVX.