Toxicity of Bacillus thuringiensis delta-endotoxins against bean shoot borer (Epinotia aporema Wals.) larvae, a major soybean pest in Argentina |
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Authors: | Sauka Diego H Sánchez Jorge Bravo Alejandra Benintende Graciela B |
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Institution: | Bioinsumos Microbianos, Instituto de Microbiología y Zoología Agrícola, INTA., CC. No. 25 (1712) Castelar, Buenos Aires, Argentina. dsauka@cnia.inta.gov.ar |
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Abstract: | The toxicity of seven Bacillus thuringiensis Cry protoxins was tested against neonate larvae of Epinotia aporema, a major soybean pest in Argentina and South America. The most active protoxins were Cry1Ab and Cry1Ac, with LC50 values of 0.55 and 1.39 microg/ml, respectively. Cry1Aa, Cry1Ba, Cry1Ca, and Cry9Ca protoxins were equally toxic with LC50 values about 4 microg/ml, whereas Cry1Da was not toxic. The synergistic activity of different protoxin-mixtures was also analyzed, no synergistic effect between the Cry proteins was observed, with the exception of the poorly toxic Cry1Ba/Cry1Da mixture that was slightly synergistic. The binding capacity of individual Cry1 and Cry9Ca toxins to brush border membranes of E. aporema was also determined. The non-toxic Cry1Da toxin was the only toxin unable to bind to E. aporema membranes. In addition the heterologous competition experiments showed that Cry1Ab and Cry1Ac toxins share a common binding site. Based on these data, we propose that Cry1Ab and Cry1Ac toxins could be used in the biological control of E. aporema. |
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Keywords: | Bacillus thuringiensis Epinotia aporema Cry proteins |
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