Further, genetic engineering allows introducing one or two well-characterized genes at a time. There is no need for the extensive backcrossing done in conventional hybridization to remove undesirable genes. Several methods are now available to transfer genes into rice. So far, the protoplast system, and biolistic and Agrobacterium -mediated gene transfer are noteworthy. All three methods have produced fertile transgenic rice.
Protoplasts are plant cells freed of their cell wall by enzymatic digestion.
Protoplasts can uptake foreign DNA after treatment with polyethyleneglycol, a neutral polymer, or application of an electric current in a process known as electroporation. In the biolistic method, also known as particle bombardment, DNA associated with tiny gold particles is shot into cells with a burst of high pressure. Agrobacterium -mediated transformation makes use of a species of plant parasitic bacteria, Agrobacterium tumefaciens , which harbors a virus that is capable of inserting its DNA into plant chromosomes. Marker genes and promoters. When the appropriate antibiotic or herbicide was present, these selected genes permitted the few transformed cells to grow while non-transformed cells died.