Source: CropBiotech Update

Rice is an important cereal grain crop worldwide. In Vietnam, it is cultivated on 5.9 million hectares, and provides 80% of the carbohydrate and 40% of the protein intake of the average Vietnamese. Rice production has increased in the country, but insect pests, such as the yellow stem borer, lead to severe crop losses. Pest control measures using pesticides are largely ineffective, since the insect larvae feed inside the rice stem. Attempts to incorporate resistance to yellow stem borer to rice by conventional breeding methods have failed due to lack of suitable genes in the rice gene pool. The transfer by genetic engineering of the Bt toxin gene (cry) from the soil bacterium Bacillus thuringiensis offers therefore an alternative solution. Bt toxins are highly specific to certain insect species larvae.

Scientists are now developing two-toxin Bt crops to slow down any resistance insects may have to the Bt toxin. This “pyramiding” technique also results in hybrid toxins with increased potency.

In the latest issue of Crop Science, researchers find out that “Translational Fusion Hybrid Bt Genes Confer Resistance against Yellow Stem Borer in Transgenic Elite Vietnamese Rice (Oryza sativa L.) Cultivars.”

The group, led by N.H. Ho, is composed of scientists from Vietnam’s Institute of Tropical Biology, the Louisiana State University AgCenter, the International Rice Research Institute (IRRI), and INRA's Campus International de Baillarguet, France.

Scientists used a Bt fusion gene, which translates a single Cry1Ab-Cry1B fusion protein, and they introduced the transgene into cells of Vietnamese rice cultivars. They then confirmed the presence of the fusion protein in transgenic plants, analyzed the progenies for the presence and stability of the transgene; and assessed the efficacy of the transgenic plants against yellow and striped stem borers. The authors report that the Bt fusion gene confers 100% mortality of yellow and striped stem borer larvae within one week of infestation with no negative effects on yield.

Subscribers to Crop Science can read the complete article at http://crop.scijournals.org/cgi/content/full/46/2/781.