Occurrence of Bacillus thuringiensis harboring insecticidal cry1 genes in a corn field in Northern ItalyCesare Accinelli1, Maria Ludovica Saccá1, Gianumberto Accinelli2 and Stefano Maini1
1 Department of Agro-Environmental Science and Technology, University of Bologna, 40127 Bologna, Italy
2 Riff98 Entomology, 40138 Bologna, Italy
Accepted 16 June 2008; published online 30 August 2008
Abstract - Bacillus thuringiensis (Bt) is a ubiquitous bacteria widely used as a biopesticide to control a number of important insect pests. Since the mid-1990s, genetically modified (GM) plants expressing Bt genes have been used as an effective tool to control a wide range of insect pests. In recent years, a wide number of articles addressing the environmental impact of genetically modified plants have been published. However, only a few have addressed the occurrence and distribution of the indigenous Bt population in agricultural systems. Here, culturing and molecular methods were used to study the occurrence of Bt harboring insecticidal cry1 genes in a corn field. Samples of corn leaves and soil were collected in July and August 2007 from a 10 ha corn field in Northern Italy. The results showed that the highest Bt density was in leaves located near the soil surface. The incidence of Bt isolates harboring antilepidopteran cry1 genes was 42% of the total tested isolates. Approximately 20% of the Bt isolates harbored the cry1Ab and cry1Ac genes. Similarly to Bt density, the highest abundance of isolates harboring cry1 genes was found in leaves collected near the plant collar. Less than 9% of the Bt isolated from soil harbored cry1 genes. Density of Bt was reduced by application of the insecticide chlorpiryfos. This effect appeared to be due to simply washing off effects of the insecticide treatment to the corn phyllosphere. This study showed that Bt was fairly abundant in the corn agroecosystem and that the high incidence of isolates harboring antilepidopterean cry1 genes could have a role in preserving the sustainability of the agroecosystem.
Key words: Bacillus thuringiensis / corn phyllosphere / epyphitic bacteria / chlorpyrifos
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© INRA, EDP Sciences 2008