Effects of Bacillus thuringiensis -endotoxins Cry1Ab and Cry1Ac on the coccinellid beetle, Cheilomenes sexmaculatus (Coleoptera, Coccinellidae) under direct and indirect exposure conditions

Dhillon, M K and Sharma, H C (2009) Effects of Bacillus thuringiensis -endotoxins Cry1Ab and Cry1Ac on the coccinellid beetle, Cheilomenes sexmaculatus (Coleoptera, Coccinellidae) under direct and indirect exposure conditions. Biocontrol Science and Technology, 19 (4). pp. 407-420. ISSN 0958-3157

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Abstract

Genes encoding cry1Ab and cry1Ac δ-endotoxins from the bacterium, Bacillus thuringiensis (Bt) that have been incorporated in several crops to enhance their resistance to insect pests may possibly influence the activity and abundance of natural enemies of insect pests. The ladybird beetle, Cheilomenes sexmaculatus (L.) might ingest Bt toxins expressed by genetically modified plants by feeding on aphids, early instar larvae of lepidopterans, and other soft bodied insects feeding on transgenic plants. Therefore, we studied the effects of Cry1Ab and Cry1Ac Bt toxins on C. sexmaculatus under direct and indirect exposure conditions. For direct exposure, the neonate C. sexmaculatus larvae were fed either pure 2M sucrose (control) or sucrose solution containing Cry1Ab or Cry1Ac (0.1%), and on alternate days with aphids till pupation. Direct exposure of C. sexmaculatus larvae to Bt toxins resulted in reduced larval survival and adult emergence as compared to the controls, which might be due to long-term direct exposure. However, there were no adverse effects of the Bt toxins on C. sexmaculatus when the larvae were reared on Aphis craccivora Koch fed on different concentrations of Cry1Ab or Cry1Ac in the artificial diet. A significant and positive correlation was observed between the presence of Bt toxins in aphids, and coccinellid larvae and adults (r=0.53** to 0.86**). The results suggested that a direct exposure to Bt toxins expressed in transgenic plants or predation on H. armigera on Bt-transgenic plants will have little effect on the activity and abundance of the ladybird, C. sexmaculatus.

Item Type:	Article
Divisions:	UNSPECIFIED
CRP:	UNSPECIFIED
Subjects:	Others > Agriculture-Farming, Production, Technology, Economics
Depositing User:	Library ICRISAT
Date Deposited:	29 Aug 2011 03:30
Last Modified:	29 Aug 2011 03:30
URI:	http://oar.icrisat.org/id/eprint/346
Official URL:	http://dx.doi.org/10.1080/09583150902783801
Projects:	UNSPECIFIED
Funders:	Swiss Agency for Development and Cooperation, Government of India - Department of Biotechnology
Acknowledgement:	The technical support of ICRISAT entomology staff during the studies, help in statistical analysis of the data by Mr Ravi Devulapalli, and funding by Swiss Agency for Development and Cooperation (SDC), Berne, Switzerland and the Department of Biotechnology (DBT), New Delhi, India, is gratefully acknowledged.
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