Crop Biotech Update

Impact of Bt Maize Cultivation on Maize Virus Distribution

January 16, 2009

Genetically modified, insect resistant maize was first cultivated in Spain in 1998. GM maize growing areas reached 64,200 ha in 2006, with 85 percent of the transgenic maize crop originating in the northeastern region of the country. Spain is the largest GM maize producer in the European Union. Bt-maize has proved to be an excellent means to control corn borers. Increased densities of aphids and leafhoppers, however, have been recorded in some Bt-maize fields. These non-target arthropods are vectors of viruses infecting the crop. In a study published by Transgenic Research, researchers from the University of Lleida evaluated the changes in the distribution and abundance of maize viruses in Spain after 9 years of large-scale cultivation of Bt-maize.

The maize dwarf mosaic virus (MDMV) was found to be the predominant virus in Bt-areas, and maize rough dwarf virus (MRDV) was found to be common in non-Bt-areas, with MRDV an emergent virus in both types of areas. Data obtained from 2001 to 2006 in experimental fields showed non-significant differences between the infection rates exhibited by two generations of Bt varieties and the non-transformed isogenics varieties for any of the viruses. The researchers concluded that differences in virus distribution are linked to the genetic background of the maize varieties and the distribution of virus reservoirs rather than to Bt-maize cultivation.

The full article is accessible at