Most, if not all, plant breeders have two things in common--patience and a tan. Patience, because it takes 10 to 12 years to develop a new plant variety using traditional techniques. And a tan, because the breeder usually spends a major part of those years outside, walking around test plots, evaluating the many generations of plants that are required to produce a new variety.
Plant breeders at Oregon State University and other educational and research agencies throughout the world have spent years in the field developing new plant varieties with increased yield potential, enhanced quality in the end-use product, and increased resistance to diseases, insect pests and drought. Their efforts have saved growers millions of dollars in crop management costs and earned billions of dollars for the world's agricultural economy.
Now, the plant breeders' craft is headed into an exciting new direction where breeders will use genome maps and DNA markers to find their way.
These terms are part of the language of molecular genetics, a field of study that began slowly several decades ago, but is rocketing forward today. Molecular genetics is the study of the function of genes at the molecular level in living organisms.
Since the 1920s, many scientists have studied DNA and its function as the repository of genes that determine the characteristics of all living things. A major breakthrough came in 1952 when James Watson and Francis Crick introduced their model of the DNA molecule. Their discovery jump-started the race to understand how DNA and genes work. The goal of much of this research is to find ways to manipulate genes in beneficial ways.
But wait a minute. Isn't that what plant breeders have been doing all along? Yes, but the traditional plant and animal breeding that has gone on for centuries has mostly used the techniques of hybridization and selection. This means that the breeder selects parent animals or plants that have desirable characteristics and breeds them to produce offspring with the good features of both parents.
Using traditional techniques, the breeder works with physically expressed traits in plants or animals. Using the techniques of molecular genetics, plant breeders can identify and manipulate genes linked to specific markers. A marker can be an observable trait that indicates the presence of a particular gene, or at the DNA level, a marker is a reference point on a chromosome. The old plant breeding techniques rely on patience, determination and, sometimes, luck. The new techniques offer the hope of greater efficiency and require surgical precision.
"The field of molecular genetics, which is about 20 years old, holds tremendous promise for producing new varieties of plants with all kinds of favorable characteristics," said Mike Burke, an associate dean of Oregon State University's College of Agricultural Sciences. "And the use of gene technology will allow breeders to do more of the breeding work in the lab and greenhouse, which will make it possible to develop new plants more quickly. The savings in time will allow plant breeders to respond more directly to market needs for particular kinds of agricultural commodities."
Many people think molecular genetics research has been going on a long time, Burke noted. But molecular genetics is a relatively new field, he said. For example, there are genome mapping projects in OSU's Department of Crop and Soil Science that began just a decade ago.
Pat Hayes, a barley breeder in the department, has been part of a national barley genome mapping project since the mid-1980s. What is a genome map? Think of it as an owner's manual for the barley plant. In term of genes, it tells you where everything is.
"The genome map of barley shows the potential genetic variation of this crop," said Hayes. "In mapping we're trying to develop a sense of where and what 100,000 genes are doing in a plant.
"These genes are functioning in this incredibly coordinated system that determines how these plants grow and develop," he added. "When we go in and begin moving things around, having a map of these genes in hand allows us to do a better job of planning the changes we will make."
Although the initial stages of genetically engineering new plant varieties takes place in the lab and greenhouse, Hayes emphasized that "we're not talking about eliminating field testing.
"That kind of testing is required to prove what we do in the lab and greenhouse works," he said. "What this technology can do is shorten the time between the idea stage and actually getting something out there that growers can use."
According to Hayes, a critical aspect of mapping is that it allows plant breeders to get an idea of how genes are linked to each other. Most inherited traits are complex, meaning they may be determined by more than one gene and may affect expression of many traits in a plant. Because of this complexity, the plant breeder usually introduces multiple traits in trying to get one desired trait. Mapping allows plant breeders to see what other characteristics are linked to that one trait.
"Possessing that knowledge before starting a plant breeding project can save time and frustration if a desirable gene is linked to undesirable genes that will make the new plant variety useless to growers," Hayes said.
Hayes has used maps to find genes that offer resistance to stripe rust, a disease that can cut barley yields and is a problem in Oregon. He and colleagues have successfully bred these genes into new varieties of barley. Field testing of these potential new varieties is now underway.
"These new technologies, mapping as well as transformation techniques where genes are introduced into plants at the chromosome level, are gradually becoming a standard part of the plant breeder's array of tools," said Hayes. "In mapping we've made tremendous strides in the past three years. As we reach each new level in this technology we can see new levels ahead that we want to get to."
Hayes isn't the only plant breeder conducting a gene mapping project at OSU. Hayes' colleague Steve Knapp is a plant breeder specializing in rapeseed and sunflower seed crops. He is conducting gene mapping and genetic breeding projects for both crops, grown for oils used as machinery lubricants. According to Knapp, the application of genetic engineering techniques in oil seed crops research is increasing every year.
"It's just a matter of time before the use of genetic technologies becomes a routine part of oil-seed breeding programs," he said. He added that the limiting factor in employing genetic technologies is cost, in many cases.
"Not all crops are the same when it comes to using gene engineering techniques on them," Knapp said. "It is relatively easy to use these techniques with rapeseed and therefore the cost of the technology is reasonable. On the other hand, using transformation techniques--where genes are transferred from the DNA of one cell to another cell--is difficult with sunflower, making the cost of engineering projects with sunflower very expensive."
An important factor in the continued use and development of genetic technologies in plant breeding is the role industry plays, Knapp commented.
"In some crops such as corn and soybeans, private companies have a lot invested and a lot of genetic research is being done," he said. "These companies don't always share their research with scientists at public universities, but there is cooperation towards the common goal of advancing the technology."
Wheat, a dominant agricultural commodity in Oregon and the Pacific Northwest, hasn't lagged behind in adoption of gene technologies for breeding purposes.
Jim Anderson, a research geneticist with the U.S. Department of Agriculture's Agricultural Research Service (ARS), has been conducting a wheat genome mapping project since coming to the Pacific Northwest last year. Anderson is responsible for breeding improved varieties of club wheat, a type that is mixed with other kinds of wheat to make flour for pastry and other products. He is headquartered at Washington State University in Pullman and works directly with ARS, OSU and WSU wheat scientists.
"With club wheats, we're getting to the point where we know what kind of effect specific genes have and we can identify these genes through the use of markers," said Anderson. "These advances will allow us to move those genes around more effectively."
According to Anderson, the use of these techniques and the information they provide will allow wheat breeders working in the lab and the greenhouse to move a single gene into an adapted plant in as little as two or three years. In traditional plant breeding where the scientist, working in the field, has to confirm the presence of the gene just by looking at the plant each growing season, that could take 7 to 10 years, he said.
The shorter development time is possible, said Anderson, because, "We're looking at the DNA level so we know the gene is there," said Anderson. "We don't have to wait for the plant to grow to full maturity in the field to check for presence of the characteristic expressed by the gene.
"However, breeders are almost always interested in manipulating more than one gene at a time," Anderson said. "This dilutes the benefit of DNA markers, because one can monitor only so many genes simultaneously with markers using current technology.
"In most cases, the savings of time in developing new varieties using DNA markers will be one or two years," Anderson said. "The major benefit is that we can discard the undesirable plant types early in the breeding process and focus resources on the material with the most potential to become a new variety."
Anderson added that if the new plant variety turns out to be a big hit in the marketplace, saving a few years during the development process could be worth millions of dollars in terms of what the crop might earn in sales.
"The adoption of gene technologies in wheat breeding will be a gradual transition as it is has been over the past five years," Anderson said. "A lot of this was oversold early on. People were saying that field plant breeding would be a thing of the past. It's just not that simple."
Long-time OSU wheat breeder Warren Kronstad agrees that breakthroughs in molecular genetics could have great impact on plant breeding, but he stops short of saying the revolution has begun.
"The potential is certainly very great, but we're not there yet," said Kronstad. "Speaking as an applied plant breeder, I can see that it is a great advantage to be able to introduce traits in a plant by tucking genes into chromosomes at the molecular level. However, to be a successful variety, the plant requires many genes for different traits, many of which are really influenced by the environment.
"In terms of its DNA, wheat is a very complex plant," he continued. "When you try to increase genetic variability by making crosses of two plant species, the chromosomes of the two parents have to be similar or abortion will result. But having the means to move genes into chromosomes allows us to bypass the sexual cycle of the plant. In theory this capability gives plant breeders access to the whole kingdom of both plant and animal genes that they could introduce and hopefully get whatever type of trait expression is desired."
But the ability to "tuck" a gene into a chromosome is not broadly available to wheat breeders yet, according to Kronstad.
"What the science of molecular genetics can do for us immediately is to provide a greater knowledge of plant physiology and development," said Kronstad. "Being able to study a plant at the DNA level allows us to learn how gene expression takes place in plants, which we know very little about now."
Kronstad added that he hopes to enhance the molecular genetics component of the wheat breeding program by adding a full-time molecular geneticist.
"We've written a proposal requesting funding for this position and forwarded it through the OSU College of Agricultural Sciences administration to the Legislature for consideration," said Kronstad. "It's time the OSU wheat breeding program gets more directly involved in this research so we can look at the breakthroughs as they come up and decide what we can use and what we can't."