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Transgenic Bt rice expressing a synthetic cry 1B gene : expression strategies and field protection against the striped stem borer : expression strategies and field protection against the striped stem borer

Breitler J.C., Royer M., Vassal J.M., Messeguer J., Marfa V., Del Mar Catala M., San Segundo B., Martinez Izquierdo J.A., Meynard D., Guiderdoni E.. 2002. In : International Colloquium on Invertebrate Pathology and Microbial Control, Foz do Iguassu, Brazil, 18-23 August 2002 : Proceedings. Bethesda : SIP, p. 232-236. (Documentos / Embrapa Soja, 184). International Colloquium on Invertebrate Pathology and Microbial Control. 8, 2002-08-18/2002-08-23, Foz do Iguassu (Brésil).

We investigated whether the conditional, wound-inducible production of a Bacillus thuringiensis (Bt) Cry endotoxin may provide a hopeful and efficient alternative of protection from stem borer damage to the high dosage, constitutive or tissue-specific toxin delivery approach generally used in transgenic Bt crops. A synthetic cry1B gene controlled by the promoter region of either the constitutive ubiquitin (ubi) gene or of a wound-inducible proteinase inhibitor (mpi) gene from maize was introduced in rice by microprojectile bombardment. Accumulation of Cry1B from undetectable level to 0.2% of total soluble protein, 8-12 hours after mechanical wounding, was demonstrated in leaf and pith tissues of lines harbouring the pmpi-cry1B construct. In these plants, Cry1B was not detected in pollen and seed endosperm and embryo, unlike in pUbi-cry1B plants. Two out of 43 pmpi-cry1B plants were found to exhibit full protection against SSB damage. Field evaluation with artificial and natural infestations of the most promising ubi-cry1B and mpi-cry1B lines in Delta Del Ebre, Spain during the summer crop season 2001 confirmed the level of protection observed in greenhouse assays.

Mots-clés : chilo suppressalis; lutte antiravageur; oryza; plante transgénique; gène; bacillus thuringiensis; expérimentation au champ

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