Genetic and biological characterization of Bacillus thuringiensis isolates showing insecticidal activity against Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Abstract

The Colorado Potato Beetle (CPB) [Leptinotarsadecemlineata(Say) (Coleoptera: Chrysomelidae)] is the most important defoliator pest of potato crops worldwide.The developmentof resistance to virtuallyall groups of chemical insecticides, used to preventor reduce damage from this pest,has increasedtheneed for researchintoalternative methodsthat are effective andmore sustainable.Bacillusthuringiensis (Bt)toxicityfactorscan be used for boththedevelopment of microbialinsecticidesandfor theproduction of transgenicplants.Untildate,thereis only one commercialBt product(serovarmorrisonis) that producesCry3 proteinsto controlbeetle pests.ThisstudyaimedtoidentifyBtstrains,toxictospecies of thefamilyChrysomelidae (e.g.L.decemlineata), which have been selectedfor thepresenceof insecticidalgenes against coleopteranspecies. The mortality caused by a single crystalproteinconcentration of the different Bt strainswas determined in second instarsof L. decemlineatain a preliminaryleaf bioassay. The relativepotency of Bt strainsagainstL. decemlineatalarvae neonate,was comparedto thatof the Bt strainused as the active ingredientin the commercial productNovodor®.We discussthe potential of each Bt strainas a controlagentfor beetle pests in view of the crygenes theycarry