Silvio Alejandro López-Pazos

Cry1B and Cry3A are active against Hypothenemus hampei Ferrari (Coleoptera: Scolytidae).

Cry1B and Cry3 proteins from Bacillus thuringiensis are toxic to beetles such as the colorado potato beetle and the cottonwood leaf beetle. We report the development of a suitable rearing, bioassay method and the toxicity of these Cry proteins to coffee berry borer first instar larvae.

Activity of Bacillus thuringiensis hybrid protein against a lepidopteran and a coleopteran pest.

The use of Cry proteins from Bacillus thuringiensis are an important strategy for biological control. Recently it has been demonstrated that Cry hybrid proteins (by domain swapping) resulted in improved toxicities in comparison with parental proteins. Here, an SN1917 hybrid toxin was constructed and tested against Colombian pest insects Tecia solanivora (Lepidoptera: Gelechiidae), a severe potato pest, and Hypothenemus hampei (Coleoptera: Scolytidae), which attacks coffee crops. The SN1917 protoxin had a concentration causing 50% mortality (LC(50)) of 392 ng cm(-2), and SN1917 toxin showed an LC(50) of 201 ng cm(-2) against T. solanivora first instar larvae. The two parental toxins (Cry1B and Cry1I) used to make this new hybrid protein caused a mortality of 60% and 52%, respectively. Unfortunately, H. hampei first instar larvae proved to be resistant to the toxin. We conclude that SN1917 is an option for biological control and resistance management of T. solanivora. Implications for H. hampei are discussed.

Determination of Cry toxin activity and identification of an aminopeptidase N receptor-like gene in Asymmathetes vulcanorum (Coleoptera: Curculionidae)

An emergent pest is the weevil Asymmathetes vulcanorum, an insect that attacks Colombian potato areas. Here, some Cry proteins from the entomopathogenic bacteria Bacillus thuringiensis were evaluated as biological control strategy. It was found that Cry1B protoxin caused a mortality of 40% with a dose of 8000 ng/cm(2). Also in this research, it was identified a full length cDNA of an aminopeptidase N, a possible Cry protein receptor located in the insect midgut. This is the first report about B. thuringiensis as an alternative method for control of A. vulcanorum in Colombia.

Biological Activity of Insecticidal Toxins: Structural Basis, Site-Directed Mutagenesis and Perspectives

Insect pests destroy about 18% of crop production each year and transmit disease agents (Oerke & Dehn, 2004). Beetles (order Coleoptera) are the largest and most diverse group of eukaryotes. They contain species of harvest pests that produce major losses around the world (Wang et al., 2007). Some examples of coleopteran pests follow: Dectes texanus [Coleoptera (order): Cerambycidae (family)], attacks soybeans; Tribolium castaneum (Coleoptera: Tenebrionidae), a biological problem of stored products; Hypothenemus hampei (Coleoptera: Scolytidae), an entomological problem of coffee crops; and Premnotrypes vorax (Coleoptera: Curculionidae), a potato pest in South America (Abdelghany et al., 2010; Tindall et al., 2010; Lopez-Pazos et al., 2009b; Pai & Bernasconi, 2008; Damon, 2000). Lepidopteran species constitute an important group of harmful harvest pests that affect commercial agriculture. Among them are the following: the cotton bollworms, Helicoverpa armigera and H. zea (both Lepidoptera: Noctuidae); Tecia solanivora (Lepidoptera: Gelechiidae), a pest in potato crops of the Americas; Plutella xylostella (Lepidoptera: Plutellidae), of great importance in cruciferous crops; and the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), which causes losses in corn, cotton and rice (Keszthelyi et al., 2011; Du et al., 2011; Chagas et al., 2010; Suckling & Brockerhoff, 2010; Bosa et al., 2006; Monnerat et al., 2006).

Bacillus thuringiensis: en el manejo del agente de la pudrición blanda de la papa Erwinia carotovora

In Colombia the potato crop is the fourth in importance in the economy of the country, its production reached 300 million tons. Erwinia carotovora is a Gram-negative bacterium, facultative anaerobic which causes the soft rotting of the potato; it can potentially generate up to 100% damage in the crop, which causes large economic losses. It has been established that the bacterium Bacillus thuringiensis is able to suppress the virulence of E. caratovora because it produces N-acyl-homoserine-lactonasa, a powerful enzyme that degrades of N-acyl-homoserinolactonas, which are indispensable in the quorum-sensing mechanism of E. caratovora . This can be an important alternative for the control of the disease of the soft rotting of the potato. Considering the above, this article describes the process used by the bacterium B. thuringiensis to inhibit the activity of E. caratovora .

La biotecnología de Bacillus thuringiensis en la agricultura

Bacillus thuringiensis (Bt) is a Gram-positive rod-shape bacterium that during its sporulation phase produces a parasporal inclusion formed by Cry proteins having biological activity against pest insects. Because of these proteins, Bt shows toxicity toward pest insect larvae of Lepidoptera, Coleoptera and Diptera orders among others, besides of friendly with the environment, and for this reason Bt has a very common use for commercial products and transgenic plants with Cry protein basis in agriculture. In this review is described the most important Bt factors and their application as biotechnological tool in agrobusiness, considering Bt bioassays.