Biotechnology enthusiasts are fond of characterizing crop genetic modification as a continuation of age-old processes of alteration of nature. This is true in some limited senses; all major crop plants have been modified through their interaction with humans, most to the point of being incapable of reproducing in the wild. However in most respects it is profoundly different. For instance, genetic modification is pivotal role in establishing patent rights over crop genetic material in a way that conventional breeding never was, which is of critical importance to developing countries (see Stone 2002, Genetic Modification and New Controls on Productive Forces).
There are fundamental biological differences as well. Conventional breeding, whether carried out informally by farmers or in formal breeding programs, operates at the level of the phenotype: the plants themselves are manipulated to guide the natural processes of reproduction. Genetic modification operates at the level of the genotype: laboratory-manipulated ("recombinant") DNA is inserted into plants. This allows the transfer of genetic material across the biological kingdoms: viral and bacterial genes can be inserted in plants in a manner impossible in conventional breeding.
The two main methods of genetically modifying plants are by the use of Agrobacterium and by particle bombardment using a "gene gun." Each method is illustrated here by projects directly relevant to agriculture in developing countries, carried out at ILTAB in the Donald Danforth Plant Science Center.