The vast majority of acres now planted worldwide to GMO crops have been engineered via rDNA techniques to be resistant to herbicides or to produce Bt toxins in cell tissues , for control of certain Lepidopteran insects. These applications have proven costly and sometimes erratic in the field, in part because of gene silencing and pleitropic effects .
Questions remain over environmental impacts and food safety.
They utilize emerging knowledge of gene location and function to guide breeders in the application of conventional and innovative breeding techniques that do not rely on a transgene with a promoter and marker genes. The Genetics and Exploitation of Heterosis in Crops is published by the American Society of Agronomy, and the Crop Science Society of America.