How are Plants Genetically Engineered?

Several methods of plant engineering have been tried, but only two patented methods are used today.

One is the "gene gun" method, which fires gold- or tungsten-coated micro-particles into target cells or tissues. Genes are integrated into the chromosomes of the target cells. Hand-held guns have recently been developed to make the technology more widely available.

The other method uses "agrobacterium" a soil bacterium that naturally transfers DNA to its plant host. Agrobacterium causes diseases in its plant hosts, however, genetic engineers have developed strains from which its ability to cause disease has been removed.

Modified agrobacterium carries genes into the plant host enabling it to integrate with the host DNA. This method has the advantage of simplicity in laboratory applications. One drawback is that occasionally DNA from the bacteria may get transferred along with the transgene. The carrier itself may exist in the transformed plants for up to a year after modification.

The accuracy of the insertion of transgenes is impeded due to the inability to direct the implant to a specific point in the host incorporation is random. Since this can effect the efficiency of the transgene, it's often necessary for the researcher to produce many individual transgenic plants in order to develop a breeding line with all the desired characteristics.

Using transgenics in this way, scientists have bred several varieties of crops resistant to various pesticides and herbicides. So far at least 38 different crop species have been genetically engineered and tested in field trials.