Diversity of Bacillus thuringiensis strains from Colombia with insecticidal activity against Spodoptera frugiperda (Lepidoptera:Noctuidae)

Abstract

Aims: To identify and characterize Bacillus thuringiensis strains highly toxic to Spodoptera frugiperda, and to explore the genetic diversity of such strains. Methods and Results: The insecticidal activity of 1100 strains of B. thuringiensis from Colombian soil samples was assayed against ®rst instar S. frugiperda larvae, and 32 active strains were found. After a second bioassay evaluation, the eight most potent strains were selected for further characterization, which included crystal protein pro®les determined by polyacrylamide gel electrophoresis, plasmid pro®le, plasmid restriction patterns, cry gene composition, qualitative determination of b-exotoxin production, random ampli®ed polymorphic DNA, serotyping, and toxicity to S. frugiperda. All Colombian strains contained cry1Aa, cry1Ab, cry1Ac, cry1B, cry1C and cry1D genes. However, PCR pro®les of the Colombian strains suggested the presence of variants of the cry1 genes. Serotyping indicated that these strains belong to the kurstaki, thuringiensis, canadiensis and indiana subspecies. Interestingly, three strains belonging to different serotypes and subspecies were found in the same soil sample, and toxicity ranged between 11 and 976 ng cm ±2 of diet. Conclusions: It has been shown that B. thuringiensis strains belonging to different serotypes and displaying variable potency to S. frugiperda larvae can be found in the same soil sample. Signi®cance and Impact of the Study: The results obtained indicate that some of the B. thuringiensis strains studied could be of interest for further development for S. frugiperda control programmes.

In vivo binding of the Cry11Bb toxin of Bacillus thuringiensis subsp. medellin to the midgut of mosquito larvae (Diptera: Culicidae)

“…Mosquitoes were fed with soybean powder. S. frugiperda was fed with an artificial diet based on bean (Arango et al 2002), and included as a negative control in which binding of Cry11Bb protein is not expected to occur.…”

Characterization of insecticidal crystal proteincry gene ofBacillus thuringiensis from soil of Sichuan Basin, China and cloning of novel haplotypescry gene

“…In order to solve these problems, isolation of new strains and toxins are crucial. Many scholars had isolated some novel variations from Bt in the world (Bravo et al, 1998;Iriarte et al, 2000;Arango et al, 2002;Merdan and Labib, 2003;Uribe et al, 2003;Chen et al, 2004;Vilas-Boas et al, 2004;Luo et al, 2005).…”

Identification and bioactivity of native strains of Bacillus thuringiensis from grain-related habitats in Turkey

“…They are important for reflecting biodiversity through sampling sites and finding new strains with high toxicity against target insect species. Strains in the collections are characterized by a number of different methods to identify and to test and confirm their toxicity against different insect orders (Arango et al, 2002;Wang et al, 2003;Tamez-Guerra et al, 2004;Martinez et al, 2005). Identification of cry gene content by PCR is the most effective technique in screening large native collections to predict insecticidal activities of individual strains (Ben-Dov et al, 1997;Porcar and Juarez-Perez, 2002).…”