Characterization of a Bacillus thuringiensis strain toxic against lepidoterans and coleopterans.

BERÓN, C.; SALERNO, G.

Foz do Iguassu. Brasil

Congreso; XXI International Congress of Entomology; 2000

Bacillus thuringiensis is a spore-forming bacterium producing upon sporulation a parasporal crystal toxic to some invertebrates, mostly insects and nematodes. The parasporal inclusion body in composted of proteins, or d-endotoxins, varying in quantity and type depending of the strain. The search for novel strains is potentially important to obtain more potent isolates than those commercially available and to expand the insecticide spectrum against resistant insects. In a project oriented to search for novel native strains in Argentina, the FBt 7 isolate was obtained from soil samples collected in the province of San Luis. Phase contrast microscopy (1,000X) and scanning (15,000X) and transmission (25,000X) electron microscopy revealed the presence of a rounded inclusion which is morphologically different from the typical crystals found in serovar kurstaki, tenebrionis and israelensis. The crystals were purified by sucrose gradients (55–82 % w/v) and the apparent molecular masses of the toxin polypeptides were determined by SDS-PAGE. The electroforetic pattern showed the presence of two major polypeptide bands at 80 and 130 KDa. The toxicological characterization of the toxin was performed using spore-crystal complex against larvae of two lepidopteran (Anticarsia gemmatallis and Spodoptera frugiperda), two coleopteran (Diabrotica speciosa and Tenebrio mollitor) and one diptera species (Aedes agypti). Mortality was observed in a preliminary assay against lepidopteran and coleopteran species. Further characterization of this strain is in progress.