Friday, 23 January 2015

Conventional Breeding v/s GM plants

Conventional plant breeding involves changing the genes of a plant so that a new and better variety is developed. New varieties of plants are bred to suit different climate conditions, improve taste or nutritional value, cope with disease or pests better, or to use water or nutrients more efficiently for example. To conventionally breed a new plant variety two closely related plants are ‘sexually crossed’. The aim is to combine the favourable traits from both parent plants and exclude their unwanted traits in a singular new and better plant variety.
However, the progeny of this first cross inherit a mix of genes from both parent plants and so both positive and negative traits may be inherited. Breeders have to look at all the progeny and select the ones with the most positive traits and least negative traits.
This process called ‘back-crossing’ takes place over a number of generations, which usually means a number of years, until the progeny have all the desirable traits and none of the negative ones of the original two parent plants.
For example, a wheat variety that produces high yields in a one region may be susceptible to a new disease. Another wheat plant may have very low yield, but has resistance to the new disease. Breeders can cross and backcross these two parent wheat varieties and their progeny with the aim of combining the high yielding qualities from that parent with the disease resistance from the other parent.Conventional plant breeding may also use ‘wider crosses’ that involve crossing species or even genera that are quite unrelated. These crosses cannot occur without help – so sophisticated techniques are employed.
Breeding using genetic modification (GM) also involves changing the genes of a plant so that a new and better variety is developed. It is done for the same reasons as conventional breeding. The key difference is that instead of randomly mixing genes, which occurs as a result of a sexual cross, a specific gene, which is associated with a desirable trait, is selected and inserted directly into the new plant variety.
GM also allows breeders to use genes from unrelated plants and sometimes other organisms into a new variety. This means breeders can access and use a wider choice of genetic diversity to develop new plant varieties. This is possible because all genetic information is stored in DNA – which is the same chemical in all organisms.
For example, conventional breeding uses chemical and physical means to ‘mutate’ plant genes. These gene mutations may give the plant different, and even desirable, traits. Plant breeders can then select for these desirable traits caused by the mutated gene to breed new plant varieties. Mutations also occur naturally and these are also used in breeding.
Conventional breeding also crosses different species of plants to create hybrids. Plant hybrids are common in agriculture and horticulture and home gardeners would be familiar with hybrid flowers and vegetables.
Conventional breeding can also benefit from GM. For example scientists may think a particular gene is responsible for a certain desirable trait. To confirm this they can develop a GM plant using the gene in question. If this GM plant displays the desirable trait then it is likely the gene is responsible.Breeders can then go back to the original plant and start breeding to include the desirable gene using techniques like DNA markers that ‘flag’ the location of the gene making it easy for breeders to know if the gene is present or not in each new generation of plant. This method speeds up the breeding of new plant varieties. 
The unique power of GM however lies in its ability to incorporate novel genes into new plants to develop plants with properties that would not be achievable through conventional breeding. This may mean using genes from unrelated organisms such as in the case of insect-resistant GM cotton.The evolution of plant breeding has been occurring for thousands of years and GM is the latest development. Our ancestors embraced new plant breeding techniques as they emerged and we are the benefactors with a large range of new and improved plant varieties now available to us.GM is one of a suite of breeding tools that future generations can use to help tackle environmental and human health challenges.

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