Feeding trials insects have shown that some plant lectins provoke toxic effects or affect insect growth and development, which makes them putative candidates as insecticidal proteins. In this research we have evaluated the detrimental effects of lectin feeding on larval growth and development of polyohagous pest insect, Spodoptera littoralis (Lepidoptera: Noctuidae) and the monophagous tobacco hornworm, Manduca sexta (Lepidoptera: Spingidae). In this no-choice feeding experiment, caterpillars were kept on transgenic tobacco plants that express leaf and bulb lectin from garlic (Allium sativum) (ASAL and ASAII, respectively, and their weight and development into pupae were scored. Controls were fed on wild type tobacco plants. Typically, ASAL and ASAII inhibited larval weight gain and retarded normal pupal development resulting in mortality. Potential mechanisms of insecticidal activity for plant lectins are discussed.
