Characterization of a Bacillus thuringiensis strain with a broad spectrum of activity against lepidopteran insects

• Published in: Entomologia experimentalis et applicata 2004-04, Vol.111 (1), p.71-77
• Main Authors: Martinez, C, Porcar, M, Lopez, A, Ruiz de Escudero, I, Perez-Llarena, F.J, Caballero, P
• Format: Article
• Language: English
• Subjects: Aedes aegypti; Anopheles stephensi; Bacillus thuringiensis; Bacillus thuringiensis subsp. aizawai; bacterial insecticides; bioassays; bioinsecticides; Biological and medical sciences; Biological control; biological control agents; Control; cry genes; crystal proteins; Culex pipiens pipiens; Culicidae; delta-endotoxins; Diptera; Fundamental and applied biological sciences. Psychology; genes; Helicoverpa armigera; host range; insect control; insecticidal proteins; Lepidoptera; lethal dose; molecular characterization; Noctuidae; PCR; Phytopathology. Animal pests. Plant and forest protection; Protozoa. Invertebrates; Spodoptera exigua; toxicity; δ-endotoxin
• ISSN: 0013-8703; 1570-7458; 1570-8703
• DOI: 10.1111/j.0013-8703.2004.00156.x

The insect pathogen Bacillus thuringiensis is suitable for use in biological control, and certain strains have been developed as commercial bioinsecticides. The molecular and biological characterization of a Bacillus thuringiensis subsp. aizawai strain, named HU4-2, revealed its potential as a bioinsecticide. The strain was found to contain eight different cry genes: cry1Ab, cry1Ad, cry1C, cry1D, cry1F, cry2, cry9Ea1, and a novel cry1I-type gene. Purified parasporal crystals from strain HU4-2 comprised three major proteins of 130-145 kDa, which were tested for their insecticidal potency to four species of Lepidoptera (Helicoverpa armigera, Spodoptera exigua, S. littoralis, and S. frugiperda) and three species of mosquito (Culex pipiens pipiens, Aedes aegypti, and Anopheles stephensi). The crystal proteins were highly toxic against all the species of Lepidoptera tested, moderately toxic against two of the mosquito species (C. pipiens and Ae. aegypti), but no toxicity was observed against a third species of mosquito (An. stephensi) at the concentrations used in our study. The LC50 values of the HU4-2 Bt strain against H. armigera larvae (5.11 μg/ml) was similar to that of HD-1 Bt strain (2.35 μg/ml), the active ingredient of the commercial product Dipel. Additionally, the LC50 values of the HU4-2 Bt strain against S. littoralis, S. frugiperda, and S. exigua (2.64, 2.22, and 3.38 μg/ml, respectively) were also similar to that of the Bt strain isolated from the commercial product Xentari for the same three species of Spodoptera (1.94, 1.34, and 2.19 μg/ml, respectively). Since Xentari is significantly more toxic to Spodoptera spp. than Dipel and, reciprocally, Dipel is significantly more toxic against H. armigera than Xentari, we discuss the potential of the HU4-2 strain to control all these important lepidopteran pests.