Therefore, so-called marker genes are usually linked to the DNA fragments before their transfer. These marker genes can then be detected easily, enabling scientists to see whether transfer of the desired DNA has taken place. To date, the main markers used have been genes which allow the plant to grow in the presence of a specific antibiotic or herbicide. Other marker systems are being developed. The same technique can be utilised to combat the activity of plant viruses, providing a means of controlling viral infection.
Antisense technology lies behind many of the current applications of plant biotechnology.
Although genetic engineering receives much attention, of as much significance is the application of genetic mapping to plant breeding. By determining the location and likely action of many plant genes, conventional plant breeding is being conducted with greater precision, as it becomes possible to detect quickly and exactly those plants which carry desirable characteristics.