Abstract
The Andean weevil Premnotrypes vorax represents an important cause of damage to Colombian potato crops. Due to the impact of this plague on the economy of the country, we searched for new alternatives for its biological control, based on the entomopathogenic bacteria Bacillus thuringiensis. A total of 300 B. thuringiensis strains obtained from potato plantations infested with P. vorax were analyzed through crystal morphology, SDS-PAGE, PCR and bioassays. We used site-directed mutagenesis to modify the Cry3Aa protein. Most of the B. thuringiensis isolates had a bipyramidal crystal morphology. SDS-PAGE analyses had seven strains groups with delta-endotoxins from 35 to 135 kDa. The genes cry 2 and cry 1 were significantly more frequent in the P. vorax habitat (PCR analyses). Three mutant toxins, 1 (D354E), 2 (R345A, DeltaY350, DeltaY351), and 3 (Q482A, S484A, R485A), were analyzed to assess their activity against P. vorax larvae. Toxicity was low, or absent, against P. vorax for isolates, wild type cry 3Aa and cry 3Aa mutants. The genetic characterization of the collection provides opportunities for the selection of strains to be tested in bioassays against other insect pests of agricultural importance, and for designing Cry proteins with improved insecticidal toxicity.
Highlights
It has been estimated that 9000 species of insect pests affect commercial crops in the world
All B. thuringiensis isolates of their crystal protein products were further characterized by SDS-PAGE
The results revealed that the colombian P. vorax environment strains synthesize a protein, or group of proteins, with a molecular mass between 35 and 135 kDa (Fig. 2)
Summary
It has been estimated that 9000 species of insect pests affect commercial crops in the world. The entomopathogenic activity of Gram positive B. thuringiensis is mainly due to the synthesis of large quantities of insecticidal crystal proteins (ICPs), or δ-endotoxins, during sporulation that can be distinguished as distinctively shaped crystals under electronic scanning microscopy (Kati et al 2007). These inclusions are comprised of toxins known as Cry and Cyt proteins. The Andean potato weevil (or White Worm as named in Colombia) Premnotrypes vorax (Coleoptera: Curculionidae) is a major cause of damage to potato crops in the Andean regions of Colombia, affects 75% of cultivated area, and 10-90% of the potato harvest losses are due to this insect (Herrera 1997). The toxicity of the Cry 3A δ-endotoxin in P. vorax larvae was evaluated by engineering the specific residues D354, R345, Y350 and Y351 (loop I in the binding domain), and Q482, S484 and R485 (loop III) in domain II (Wu & Dean 1996, Wu et al 2000)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
