Identification of new Bacillus thuringiensis (Berliner) isolates as biological control agents against Ostrinia nubilalis (Húbner) larvae

Abstract

esThe European maize borer Ostrinia nubilalis (Lepidoptera: Pyralidae) is one of the most widely studied agricultural pests in the world. This insect feeds on many different species of cultivated plants, particularly maize, and is is widespread in Europe, North America and North Africa. It has been recently reported as an important problem in greenhouse-grown vegetable crops in southern Spain. Bacillus thuringiensis (Bt) produces a wide range of proteins with insecticidal activity against different insect pests. Commercial Bt products serovar kurstaki(DiPelR) and aizawai (XentariRri)are currently being applied to control O. nubilalis.However, these products are based on strains that produce crystals comprising of a limited number of proteins (Cry1A, Cry1C, Cry1D and Cry2A). The continual use of these products can lead to development of resistance in insect populations, as observed for Plutella xylostella in the open field (Ferré et al., 1991, PNAS 88:5119–5123) as well as Trichoplusia ni in greenhouses (Janmaat and Myers, 2003, Proc. R. Soc. Lond. B Biol. Sci. 270:2263–2270). The aim of this study was to identify Bt strains that producevery active Cry proteins which can help to delay or avoid the development of resistance in O. nubilalis populations. The molecular and biological characteristics of the selected Bt proteins will be discussed