Marker Assisted Breeding
In the News
May 28, 2014
What if you could condense decades of plant technology – and 10,000 years of plant breeding techniques – into just a couple of weeks of research, followed by incredible results? Sound impossible? It used to be, but today, plant breeders are able to speed up the process of breeding desirable traits in their fruits and vegetables through a sophisticated DNA-screening process known as marker-assisted breeding.
Traditionally, plant breeders were only able to evaluate plants phenotypically (by growing them out and observing their physical traits). Once they found sources with desirable traits, they would cross-breed them, grow out the offspring and evaluate them to see if the resulting plant contained the desirable traits. With DNA screening and DNA markers, breeders only have to wait a couple weeks – not decades – to determine if the plants contain the traits they are targeting. They simply grow out the plant into a seedling and take a leaf clipping, send it to the lab for evaluation and within a week or two they are able to determine which plants to keep and which to discard. This alone shaves off a lot of time as well enables them to screen many more plants than ever before which increases their odds of finding and developing the plants with the most genetic potential.
Why is this important? Today’s food industry is grappling with the challenge of feeding many with fewer resources, and there are other challenges to consider too, like how to transport food to consumers that won’t spoil or even lose flavor or nutritional value in the process. Then there’s the issue of meeting consumer demand for specific food qualities.
Marlin Edwards, Chief Scientist for Global Vegetable Research at Monsanto (Monsanto sponsors Food Nutrition & Science from the Lempert Report but doesn't influence, edit or see the publication before it is sent out), says that with genetic markers, breeders can now “see” inside the plants they intend to breed. Using marker-assisted breeding, their plant scientists can examine the DNA of seeds to find the ones that will produce the best plants.
Here’s how it works. First, genetic markers are identified in plants’ DNA that are linked to important traits such as disease resistance, drought tolerance, yield, taste, and so on. The markers are then used like a test to screen all of the plants available for breeding and accurately select and breed only the seeds that will produce plants with the desirable traits. This method allows a much larger population to be screened than with conventional breeding.
Once the seeds are grown out into seedlings, a tiny leaf tissue sample is taken and sent to the lab to evaluate the genetics of the plant. Samples are run through their genetic marker lab and are tested for the presence of the traits they have associated with genetic markers. The breeder then receives a report letting him/her know which plants in their breeding program have the best combination of traits they are targeting. They are then able to discard the plants without the traits of interest and only focus on the ones with the traits they are targeting. This process is used both to develop the parent lines of hybrids and to confirm that the hybrid crosses that they developed contain the traits they were targeting.
“Basically, marker-assisted breeding is like breeding with the lights on. It clues our breeders into what is going on genetically much earlier in the process,” says Edwards.
But how does all this differ from genetic engineering? Simple, says Edwards. Marker-assisted breeding utilizes the inherent genetic potential of an individual plant to enable breeders to find and develop the most promising seedling among thousands for further breeding. This method does not require the huge cost or time-consuming regulatory approval that is associated with genetic engineering. With genetic engineering, on the other hand, plant scientists can pinpoint desired traits by isolating the gene of interest and directly inserting it into another plant to produce a new generation of plants that have the targeted beneficial characteristics. And both breeding techniques have their benefits.
“The big benefit of genetic engineering is that it is a very precise method of developing new plants with a desired trait when the specific gene for that trait is well understood. Genetic engineering can play a very important role when a destructive virus or other pest can’t be controlled through breeding and is impacting a significant number of acres, such as citrus greening. What most people don’t realize is that genetic engineering still requires the use of traditional breeding and utilizes a lot of the same tools as marker-assisted breeding. Marker-assisted breeding is a less-costly and less time-consuming method due to the fact that it doesn’t have to go through the regulatory process. However, it can only provide the needed solution if the genes for the desired trait are already present in the variation available in the crop,” says Edwards.
Interestingly, marker-assisted breeding does not limit an organic farmer’s use of the resulting seeds. And vegetable seeds developed through marker-assisted breeding are grown by both organic and non-organic farmers. In fact, the varieties with good resistance to devastating diseases are extremely valuable to organic farmers, especially if they have no other natural means of controlling those diseases. The high levels of disease resistance bred into Monsanto’s vegetable seeds utilizing marker-assisted breeding are a huge benefit to growers to help them produce high-quality produce with a minimum level of pesticide applications and lower crop management costs. For organic growers, this high level of natural disease resistance can be even more important since their disease control options are more limited.
Still, marker-assisted breeding, while a powerful addition to classical breeding methods, cannot deliver some of the crop-production solutions available through GMOs, says Edwards. The two approaches have an important role to play in helping farmers produce the food we eat, but there is still a lot of confusion and misinformation around both methods and a lot of education is still needed to help consumers understand the benefits of these methods of developing better plants.
“Seeds developed through Monsanto’s traditional breeding as well as marker-assisted breeding are currently sold in over 160 countries, so farmers in both developed and developing countries are able to benefit from these improved seeds. At the end of the day, they have access to new seeds that better withstand devastating diseases and help them produce a healthy, abundant crop,” says Edwards.