Cooperative effort is powerful tool for soybean breeding programs
By Doug Rich
The key to a successful soybean-breeding program is to collect useful data every year, even when growing conditions are not ideal. Although drought could claim some field trials this year, soybean-breeding programs around the country have developed strategies to mitigate the impact of drought.
"Knowing that drought strikes in different parts of the country each year, what we in soybean breeding have done is develop a network of breeders all working on drought," Tommy Carter, Ph.D., research geneticist and soybean breeder with the U.S. Department of Agriculture Agricultural Research Service, said. "Even if it is too dry in one area we can still get data. Building in this redundancy is our single most powerful way to overcome production problems. If we did not do this it would probably cut our rate of progress in half."
Soybean breeding programs from Minnesota to Georgia participate in the Uniform Testing Program. This is a collaborative test that is not aimed specifically at building a more drought-resistant soybean. However, there are other collaborative multi-state tests that are aimed at developing a more drought-tolerant soybean, according to Carter. Each participant in the Uniform Testing Program contributes elite material for the others to plant in their field trials, and they share that data with the group. This is generally the last step before these varieties are released to the public.
"There are several of us making crosses and probably the drought does not impact making crosses that much," Carter said. "Where the drought really affects us is when we lose lines out in the field. Losing field trials is the real killer. That is why we need a network across several states."
"I don't want this to happen but I could lose a considerable amount of data from our Kansas trials and I would still have data from Missouri, Illinois, Tennessee and other regions that would show me how our entries performed," Bill Schapaugh, Ph.D., soybean breeder at Kansas State University, said. "This is good information and it helps us make decisions."
The drought could reduce seed production for potential new variety releases next year. If there is a shortage of seed for a specific new release, Schapaugh said they could go to the winter nursery.
"We can increase production that way but it adds cost to the release," Schapaugh said. "We can make up time and increase seed by going to the winter nursery."
Carter said once they identify a promising new variety and they want to increase the seed rapidly, they use the winter nurseries. USDA has a station in Puerto Rico, which is also where KSU and other universities have winter nurseries.
"It is very instrumental to our success as a plant breeding operation," Carter said. "We don't do crop testing there because in the northern region of Puerto Rico, where we are growing soybeans, it is not a drought-prone area."
During the summer months soybean breeding programs are busy making crosses to create populations for selecting new varieties. This is hard to do when it is hot and dry. When it is 100 degrees day after day, seed set from pollination will not be as good as it might have been. Schapaugh said they irrigate this nursery to improve pollination and seed set.
"We make more crosses and we try harder to compensate for the heat but it still may not all work out as we planned," Schapaugh said.
The winter nursery can be used for making crosses, also. Depending on how it is handled, they can get one or two generations in one winter season.
"The winter nursery is a very important part of our program every year, but in a year like this it becomes even more important," Schapaugh said.
Dead plants don't yield much useful data, so limited irrigation can be used to keep plants viable for research purposes.
"We know we can't let them go without water, so we have an irrigated and a limited irrigation section," Grover Shannon, head of the Southern Missouri Soybean Breeding Program at the University of Missouri Delta Research Center, said. "We put the same variety under irrigation and on the other side we induce drought."
Schapaugh said at KSU this summer every single experimental variety is in at least one irrigated location. He said they have fields on these irrigated farms where they don't irrigate as much, and some years they don't irrigate that portion of the field at all so they have dryland and irrigated comparisons on the same field.
"This year we were concerned and did some supplemental irrigation on many of those fields or just irrigated the whole field," Schapaugh said.
Carter said in his breeding experience if the yields get below 15 bushels per acre, that yield loss is primarily caused by drought stress, not genetic differences. If yields on his drought plots get that low, he believes the data is not useful.
"On the other hand if yields are in the 20- to 40-bushel range and the difference is due to drought, that is when we make our best selections for drought tolerance," Carter said.
Progress is being made in finding soybean varieties that are slow wilting and deep rooting. Shannon said researchers have brought in lines from Korea, China, and Japan and identified lines that don't wilt as quickly. These lines also seem to root better with more lateral roots in dry soil. Shannon said we can't make something yield without water, but with drought-tolerant genes we can improve yields as much as 25 percent. Some of the new lines have the ability to fix nitrogen even under drought conditions. Drought-tolerance research is a long-term project.
"I don't think we will find something that is totally tolerant of drought, like a cactus, but I think we can make progress and reduce the losses," Shannon said. "The plants will hold up longer and recover better in a dry period."
Schapaugh said he is more concerned with the effect of drought on soybean producers than on research trials. He said researchers have more flexibility and have put in place ways to mitigate the effect of drought on soybean breeding programs.
Doug Rich can be reached by phone at 785-749-5304 or by email at firstname.lastname@example.org.
"Building in this redundancy is our single most powerful way to overcome production problems," Carter said.