Marker-assisted breeding

Another screening method, called marker-assisted breeding, utilizes DNA-based technology to rapidly determine which offspring have desired genes. To better explain this, let's see an example from Dr. Oliver Dong, a researcher in Dr. Ronald's lab. So in agriculture production, very often we like to combine good traits from different plants. In this case, we may have a parental plant that sets a lot of seeds, and we have another parent which does not set a lot of seeds but has a lot of branches. Basically, we cross the two parents and we identify in the following generations the progeny that has combined good traits from both sides. In this case, it will be a plant that has lots of branches and has lots of seeds on each branch. However, there's a challenge with this approach. Think of a huge population of thousands of plants. How can you determine which one is the best one that contains the best traits? That's why we need a better method called marker-assisted breeding. So agricultural performance of plants are usually linked to traits that are encoded by DNAs. In this case, the dark circles represent good genes, which will control a good trait, whereas the open circles represent not so good genes, which will not give rise to a good trait. In marker-assisted breeding, instead of looking at the agricultural performance directly in the offspring population, we look at the genetic makeup of these plants, and we choose the individual that contains the most dark circles, or the most good genes, because this individual will have the best agricultural performance. This method allows scientists to quickly select the best individual in a relatively short period of time compared to traditional breeding. This is the method that Dr. David McKill, a rice breeder at UC Davis and the International Rice Research Institute, used to develop the original sub-1 rice strain. First, a submergent-tolerant rice strain, FR13A, was crossed with a variety of Swarna rice. Then the hybrid was crossed back to Swarna and selected over many generations to clear the undesired genetic background from FR13A. What we're left with is a robustly growing strain of Swarna rice that can withstand flooding for up to two weeks.