June 2011
Genetic Modification- what does that really mean?
Genetic modification (GM) is often a misunderstood topic which often results in a reluctance to adopt the technology.
However, when used properly, it can be a most useful technique for improving the way we grow food and the value of this food to the world’s population.
GM does not change the flavour, colour or quality of a food but rather is used to introduce a particular trait into the organism that will assist with either production or improve the nutritional quality of the end product.
Changing the genetic make-up of an organism is not a new technology.
For thousands of years humans have been breeding plants and animals for desirable traits and selecting progeny based on their ability to display these traits.
For instance, cereal crops (such as wheat, barley, oats etc) are constantly being re-bred for desirable traits, such as increased yields, disease resistance or drought and frost tolerance, by crossing with other varieties of the same species (wheat with wheat, barley with barley etc).
However, conventional cross-breeding is a slow and often costly way to ensure that an organism carries a desirable trait.
Genetic modification, however, differs from conventional breeding in that it allows a trait from an unrelated species to be inserted into the organism, which will then display that characteristic.
This is achieved by inserting the genes from one organism into the other organism (eg adding a gene to rice to increases the vitamin A content, for use in countries with vitamin A deficiencies) or by simply “switching off” some of the genes already contained in the organism (in oilseed crops this is used to turn off genes which produce unhealthy oils).
In Australia foods that have been genetically modified must undergo a safety evaluation by Food Standards Australia and New Zealand (FSANZ) to ensure that they are as safe as conventional foods before being allowed on the market.
Most Genetic modification used in Australia is on broadacre cereal and cotton crops.
One of the most widely used GM crops is cotton (over 92% of cotton grown in Australia is GM). Cotton has either one or two genes (depending on the variety) from the soil bacteria Bacillus thuringiensis (Bt) inserted which produces proteins in the leaves of the plant that, when eaten by the cotton bollworm caterpillar, causes the pest to die.
This greatly reduces the amount of pesticides used by producers to control the bollworm pest.
The other major genetic modification to crops was the introduction of the Glyphosate (the active ingredient in Round-Up® herbicide) resistant crops.
Glyphosate is a non-selective herbicide, meaning that it will kill any plant that it is applied to.
The creation of glyphosate resistant crops means producers can use this chemical to kill weeds without affecting the growth of the plant.
This allows them to have a much larger range of chemical control options and also decrease their overall herbicide use to control weeds.
While genetic modification is able to introduce desirable characteristics not available with, and far quicker than, conventional breeding, there are some disadvantages.
These GM species are still able to cross-pollinate with conventional species which has the possibility of creating resistant varieties where they were not desired.
This is also true for the insect pests that remain alive after ingesting Bt cotton, which are therefore resistant to the bacteria.
However, this can be managed through refuge crops (conventional cotton) planted alongside GM cotton which aim to ensure there are always some non-resistant pests to available to breed and pass on their susceptibility to the Bt bacterium.
While it has been suggested, there is little evidence to support that GM foods are any less safe or nutritious for the consumer and FSANZ has not found any safety issues with any GM foods they have assessed so far.
These foods must also be labelled as containing GM ingredients so that consumers have a choice when purchasing these products.
Kiri Broad