We often think of sustainable agriculture in terms of landscapes; imagining cattle grazing on pasture, diversified fields, or wildlife on the farm. But there is a smaller, easily-overlooked level that is just as crucial: the genetics of the agriculture itself. That's the scale Nancy Ehlke, a geneticist at the University of Minnesota, has been working on; taking a decades-old plant breeding program and guiding it in a sustainable direction.

"The development of superior crops is imperative to the productivity and sustainability of agriculture in this region," says Ehlke. She is leading a group of researchers in a plant breeding program designed to improve crops in a way that makes them more suitable for sustainable agricultural practices. "Genetic improvements of forages will contribute to a more cost-effective agriculture through more stable production and reduced inputs, while providing valuable environmental services," she explains.

More than twenty people are on board at different stages in the breeding, genetics, and seed production program. "We all cooperate together and bring strengths and weaknesses to the program," says Ehlke. Together, they tackle a diverse array of projects, working toward the release of plant varieties that are economically and ecologically suitable for Minnesota's farmers and the land they own.

The Art of Breeding

Let's say you are breeding plants. How does selection for sustainability work? Ehlke's team begins by selecting potential crops that would be environmentally and economically suitable for Minnesota's farms. Legumes are a good environmental choice for several reasons. In addition to being an economical source of protein and minerals for livestock, they make a quality cover crop, improve soil and water quality, reduce the need for extra fertilizer, and work well in rotational grazing systems. Because they are perennial forages, they limit the need to till land and reduce soil erosion as well.

Ehlke is focusing on a legume called birdsfoot trefoil, which she calls "an ideal legume for grazing" because it makes an extremely high quality feed for ruminant livestock. After making this initial species selection, the next step is to determine how the plant could be improved; that is, what you would be selecting for as a plant breeder. Birdsfoot trefoil, for instance, is highly susceptible to crown and root rot diseases, which cause significant economic losses for growers in Minnesota. As a result, Ehlke's team has initiated a breeding program designed to select disease-resistant plants.

In this scenario, says Ehlke, you would plant about 2,000 birdsfoot trefoil plants in a field affected with disease, then cut them short to create even further stress. When you revisit the field in two years, you select 2 to 5% percent of the original plants, based on healthy regrowth. These plants would then be isolated and naturally pollinated by honeybees. Collect the seeds, repeat the process, and if all goes well, voilà: after a few runs, you have yourself a disease-resistant crop.

Sounds simple, right? But there are always other factors to consider. Birdsfoot trefoil does not hold up well under intense grazing pressure, and like many forage legumes, its poor seedling vigor makes it difficult to establish a stand. "Establishment problems have caused limited grower acceptance of these legumes," Ehlke says. As a result, there is almost always more than one factor to consider when breeding plants.

Kura clover, which could potentially become an important forage species, is another example of a potentially excellent new species that suffers from poor seedling vigor. "If you can actually get it established, you essentially have a permanent pasture," Ehlke says. Though a permanent pasture would tremendously reduce both the cost and environmental impact of planting forage crops every year, if the seed isn't reliable - or if establishment is too difficult - farmers simply won't get on board. In the end, each species has its own drawbacks and challenges, ensuring that the breeding of improved alternative crops will be continuing over a long period of time.

Of Seed and Turfgrass

Ehlke's project is also working on breeding turfgrass, the grasses that grow on our lawns and athletic fields. In addition to their decorative effect, they prevent soil erosion, provide a cooling effect in warm weather, and clean the air. Ehlke sees these grasses as a major area of potential economic growth in Minnesota.

"The market right now is huge," she says. Sustainable and environmentally friendly turf options are in high demand. If turfgrass can be bred for pest resistance, winter hardiness, efficient water use, and tolerance to wear and tear, reasons Ehlke, people will feel less inclined to use additional inputs on their lawns, and water could be conserved as well.

Turfgrass is not being commercially grown extensively in Minnesota right now because of poor winter survival. Ehlke's project is focusing on breeding ryegrass, a grass historically used in Europe for turf. "It's a very high-quality grass, because it starts early and goes late in the fall," says Ehkle. "However, its just too cold here." Breeding ryegrass for winter-hardiness is the first step toward increasing the turfgrass market in Minnesota.

Similarly, the project is working on creating new varieties of crops for the seed production industry. "High quality seed production continues to be a factor in maintaining a healthy economy in northern Minnesota," says Ehlke. Like forage legumes, the perennial seed crops that Ehlke's team is developing allow reduced tillage and thereby protect the soil from erosion and provide wildlife habitat. They also distribute the workload across the growing season.

Here, the greatest challenge is that seed production is environmentally sensitive. What may grow well in one region may not grow at all in another. "The markets are such that if you can't grow them across a range of habitats, you can't do any good," says Ehlke. "You need a wide range of adaptability."

Native Species

The final aspect of the plant genetics project involves the native species of the Midwest. Native plants were once an important component of Minnesota prairie ecosystems, and Ehlke sees them as a unique opportunity to increase the diversity of agricultural systems. Because they are well-adapted to local climatic conditions and pathogens, Ehlke thinks they would be ideally suited to provide multiple ecological benefits. For instance, says Ehlke, the prairie legume Illinois bundleflower has the potential to be used as a perennial grain crop, as part of a forage mixture, and possibly even for biofuel. Unlike most legumes, Illinois bundleflower can be grown with warm-season grasses, drastically improving total yield of the stand.

The use of these native species is primarily limited by a lack of knowledge about their genetic diversity. "We are initiating a study to determine the amount and distribution of genetic diversity within and between native populations of grasses across Minnesota," explains Ehlke. "We want to know how similar or different these plants are." If two plants in two different regions are genetically similar, that means the plant can grow well in a wide range of habitats. On the other hand, if they are genetically different, then the plant's genetics is tied to its environment, and may not grow as well far from its source. That kind of information will be crucial in future efforts to establish native plants across Minnesota.

Breeding for farmers and the environment

"I would like to have an impact and get farmers seeds they can use," explains Ehlke. The overall goal of the team's research is to continue to find a way to provide farmers with economically advantageous crops that encourage more sustainable practices at the same time.

Nancy Ehlke: ehlke001@umn.edu