How Breeders Develop New Soybean Varieties
SOYBEAN BREEDING 101: Q&A WITH SOYBEAN BREEDER DR. GEORGE GRAEF
Every year, farmers have new soybean varieties to consider for their operation. But where do those options come from? We sat down with soybean breeder Dr. George Graef from the University of Nebraska, and asked him to answer a few questions about how new soybean varieties get to farmers—how they go from an idea to the seed bag.
SK: What’s the first step to get the ball rolling on developing a new soybean variety?
GG: We have specific objectives in mind before designing crosses. The main considerations come from visiting with farmers to know what their priority needs are. Improved yield is always a primary objective, but then we consider the target production environments, such as where the varieties will be grown. Are there any specific constraints to production in those areas that need to be considered? What production systems are prevalent in that region?
In Nebraska, where I’m located, about 50 percent of the production area may be irrigated, and 50 percent rainfed. In both systems, response to water is important. The difference is that in irrigated systems, the farmer usually has more control over the timing and amount of water that can be applied to the crop, whereas in rainfed systems the water comes when it comes. Soil water holding capacity is important, then, as well as variation in soil fertility.
SK: What do you consider next, after the production environment itself?
GG: Next, we ask about disease and insect pests. Are there any consistent issues that make resistance to that pest a necessary trait? Some areas might need varieties that are resistant to Soybean Cyst Nematode (SCN) or phytophthora root rot. Other areas might need good resistance to sudden death syndrome (SDS) or sclerotinia (white mold). The objectives and choice of parents depends on what is needed to help make soybean production more efficient and profitable. Besides thinking about the farmer and production, we also need to consider processor and end-user or customer needs. Good seed quality is important to keep in mind, both in selection of parents and in evaluation and selection of superior lines that actually get advanced for possible commercialization.
SK: So, you’ve identified the challenges you want to solve through a new variety, and the required genetic characteristics. How do you begin the breeding process?
GG: The breeding process starts with selection of parent lines that will help us meet our objectives. Do they have the traits, or complementary traits, that we need based on our goals, and what do we know about how those traits? Answers to those questions help us design appropriate breeding strategies related to types of crosses to make, along with population structure, and how to handle those populations through the inbreeding and evaluation parts of the process.
Next, we make the cross, grow plants from that cross, harvest seeds and advance the generations in off-season nurseries. That is one year after the cross. Then each plant (about 30,000 from 100 or more crosses) is harvested individually, and the seeds from each plant are planted in a progeny row.
SK: When do you know you have a “keeper?”
GG: Sometimes, certain rows just really stand out in the field, and you think you have a winner at that point. That’s happened a couple times. Other times, after the first multi-location yield test, a line or two is just head and shoulders above the rest. That also has happened, and that line stayed number one the next year, and the next, through three years of regional testing.
More often, though, several lines are close together in average performance, and some may do slightly better in certain environments, and worse in others. That’s the point at which you find some lines are pretty broadly adapted across the region, while other lines have more specific adaptation that makes them best suited for targeted production areas.
SK: Start to finish, how long does the development process take for a new soybean variety?
GG: If you’re just breeding for improved yield, with some of the important required traits to help protect that yield, the process from cross to finished variety takes five to six years. At that point, there is sufficient seed quantity to continue wide area testing and some small initial distribution. But significant increases in seed volume for larger scale commercialization will take another year or two. That makes for roughly a seven to eight year process.
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Dr. George Graef is an expert in soybean breeding and genetics, and is a professor at the University of Nebraska.