No abstract

Arcelins are abundant seed storage proteins thought to be implicated in the resistance of wild Phaseolus vulgaris (L.) genotypes against Zabrotes subfasciatus (Boheman), an important storage insect pest of common bean. Here, the insecticidal activity of the arcelin-5 variant that is present in the highly resistant P. vulgaris accession G02771 was investigated. No correlation could be established between the presence of arcelin 5 and the insecticidal effects observed in G02771 seeds. Insect feeding assays with artificial seeds into which purified arcelin-5 protein was incorporated and with transgenic P. acutifolius (A. Gray) seeds in which the arcelin-5 genes were expressed, showed that the presence of arcelin-5 proteins, even at elevated levels, was not sufficient to achieve adequate resistance against Z. subfasciatus. The same might apply to other arcelin variants. Nevertheless, as resistance is clearly closely linked to the presence of the arcelin-1 or arcelin-5 locus, arcelins remain useful markers in breeding programmes aimed at introgressing high levels of resistance to Z. subfasciatus in P. vulgaris cultivars.

IntroductionArcelins are abundant seed storage proteins thought In the continuous search for new plant genes that confer to be implicated in the resistance of wild Phaseolus resistance against insects, some interesting candidates vulgaris (L.) genotypes against Zabrotes subfasciatus have been found in the gene family of lectins and 'lectin-(Boheman), an important storage insect pest of like' proteins of the common bean (Phaseolus vulgaris common bean. Here, the insecticidal activity of the [L.]) (Chrispeels, 1997). Different members of this family arcelin-5 variant that is present in the highly resistant are thought to be toxic towards insects of the coleopteran P. vulgaris accession G02771 was investigated. No family Bruchidae, which commonly infest leguminous correlation could be established between the presence seeds and cause important (post) harvest losses. The of arcelin 5 and the insecticidal effects observed in P. vulgaris lectin gene family consists of the true lectin G02771 seeds. Insect feeding assays with artificial phytohemagglutinin ( E and L variant) and the lectin-like seeds into which purified arcelin-5 protein was incorpproteins, arcelin and a-amylase inhibitor. Phytoorated and with transgenic P. acutifolius (A. Gray) hemagglutinin (PHA) was the first member of this family seeds in which the arcelin-5 genes were expressed, to which insecticidal properties were ascribed (Janzen showed that the presence of arcelin-5 proteins, even et al., 1976). Later on, the deleterious effects on the at elevated levels, was not sufficient to achieve cowpea weevil (Callosobruchus maculatus [Fabricius]) adequate resistance against Z. subfasciatus. The same were shown to be due not to PHA, but to a contamination might apply to other arcelin variants. Nevertheless, as of the PHA preparation with the bean a-amylase inhibitor resistance is clearly closely linked to the presence of (aAI ) (Huesing et al., 1991). Some promising results the arcelin-1 or arcelin-5 locus, arcelins remain useful were subsequently obtained with the latter protein. In markers in breeding programmes aimed at introexperiments with artificial diets as well as in feeding trials gressing high levels of resistance to Z. subfasciatus in with seeds of transgenic leguminous plants, aAI displayed P. vulgaris cultivars.relatively high toxicity levels, not only to some bruchid species but also to members of other insect families