Agriculture has always focused on improving animal and plant species through favourable crossbreeding and selection. A deeper understanding of genetic mechanisms and the advancement of biotechnologies mean these processes can now be handled more efficiently. The generic term Genetically Modified Organism, or GMO, is applicable to any product created using these new technologies in genetic engineering.
Since the beginnings of agriculture, humans have been using the principles of reproduction and hybridisation techniques to modify the genetic properties of plants and animals. This enables us to take advantage of their new characteristics to facilitate breeding and cultivation, tailor them to different environments, make them more resistant to disease and pests, and enhance their flavours. As a consequence, the vast majority of the plants and animals we consume today are hybrids, produced from many years of crossbreeding, occasionally between species, and from the selection of the most effective progeny. Following the discovery of DNA as carrier of the genotype, during the latter half of the 20th century, advances in biotechnology led to more accurate and more effective control over the species improvement process by specifically and exclusively targeting certain genetic characteristics.
No single definition, no one product
The generic term Genetically Modified Organism, or GMO, is applicable to all plants and animals whose genetic makeup has been modified. The broad definition, as reflected in the one adopted in the United States, covers organisms from a wide spectrum of manipulations, ranging from classical forms of crossbreeding and selection, to forced mutation using radiation (a technique of induced mutagenesis developed in the 1930s) or exposure to mutagens, followed up by a selection of the ‘best’ variants. Mutations may also be attained by inserting or removing specific genes for targeted proteins. A narrower, but more commonly accepted definition adopted by the OECD and the European Union, is restricted to the modification of genetic makeup through genetic engineering and not by recombining ‘natural’ pathways.
Alterations by direct genetic engineering include the extinction or modification of a gene that already exists in the animal or plant, or the insertion of a new gene, taken from a closely related species or from an entirely different living organism. Products of this latter form of modification, known as transgenesis, are the ones the general public commonly considers as GMOs and which draw the most criticism, given their ‘unnatural’ aspect.
One of the most well-known examples of transgenesis is the insertion of a Bacillus Thuringiensis bacteria gene into the genome of corn or soya beans. This gene codes a toxin that kills the corn borer (Ostrinia nubilalis), an insect that infests plants.
Inserting or modifying specific genes in plants endows the genetically modified versions with new attributes, such as resistance to pests (as with Bt-corn) or tolerance to specific herbicides (such as RR1 soybeans, resistant to glyphosate). It may also enrich the nutrients in food (as with golden rice, enhanced with provitamin A), or enable it to be kept for longer (for example, the Arctic apple, which does not turn so brown once cut).
In 2016, a total of 29 plant species had been genetically modified, although only a small percentage of the variants are actually produced and marketed. These mainly comprise 33 variants of corn, 20 variants of soya bean, 16 variants of cotton, six variants of potato, two variants of papaya, squash, rapeseed, and alfalfa, and one genetically modified variant of the apple and of sugar beet.
The Flavr Savr tomato is widely acknowledged as the first ever GMO to be marketed. This tomato, rendered more resistant to rotting, was launched on the US market in 1994, and withdrawn three years later. It was a commercial flop as it proved expensive for the consumer and had a somewhat mediocre flavour. If, however, we extend the definition of a GMO to include both transgenesis and mutagenesis-based organisms, products such as Ruby Red grapefruit, Calrose rice, and some 3200 other plants may be considered as ‘mutant’ variants. Such GMOs have been part of our diet for decades, and some have even been marketed as organic.