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Emerging research in Sheridan explores weevil-resistant varieties of alfalfa

by Wyoming Livestock Roundup

Last year, researchers at the University of Wyoming Sheridan Research and Extension Center began to investigate the possibilities of creating weevil-resistant alfalfa varieties for commercial growers.

After working with grapes for nearly 12 years, Assistant Professor of Horticulture Sadanand Dhekney believes that similar genetic engineering technology from grape research can be translated to producing alfalfa with weevil resistance.

“This is a pilot project. We have to establish a cell culture for alfalfa. Once we establish a cell culture system, we will have a means of inserting genes, and we can engineer plants,” Dhekney explains.

Some alfalfa varieties respond well to growing in a cell culture, but others are more difficult, and the project is currently trying to identify which varieties will be ideal for the research.

Commercial crops

“We are testing commercial varieties that are grown in Wyoming,” he notes. “Once that is optimized, we can start inserting genes for insect resistance.”

So far, one model variety has shown a lot of promise for the project but researchers hope to be able to use commercial varieties that are important to Wyoming growers as well.

Surprisingly, Dhekney is finding quite a bit of variation in how alfalfa varieties respond to growing in the cell culture.

“I would expect to see some difference, but it’s interesting to see that some varieties respond right away and other varieties take more time. That might be a potential challenge if we have to spend a lot of time optimizing the cell culture system and the engineering system to where we can have plants that growers are actually interested in,” he comments.

Growing cell cultures

Other variables can also affect how plants respond to the cell culture, such as seasonal factors like light and temperature.

“When we get material from plants growing in the greenhouse for cell culture, our plants might respond really well in the summertime but really poorly in the wintertime,” he cites as an example.

To create weevil-resistant alfalfa, researchers are hoping to use genetics that cause the plants to produce a protein called lectin, which binds to carbohydrates in the gut of the insect, making the carbohydrates unavailable for digestion. Known as antifeedants, these particular proteins essentially cause the weevils to starve and die.

“Genes for insect resistance come from different plant sources. We are currently getting them from rice, and we have some genes from maize. We also have lectin genes from bulbs that typically produce these antifeedants,” remarks Dhekney.

Eventually, if researchers see positive results, they may be able to isolate genes from the alfalfa itself to be used in future engineering.

Similar genetic information may also prove to be useful for controlling other pest problems, such as stem nematodes, which have also caused large problems for growers in Wyoming.

More questions

“We are just starting to scratch the surface. The first step is identifying those genes that show resistance and identifying the right plants. From there on, the options become unlimited, and it opens up a whole new world,” he says.

Once weevil-resistant plants are identified, a series of new questions will arise, such as how resistant plants impact livestock that consume it as forage.

“One of the reasons we chose to work with lectins from bulb plants is there have been some studies that have shown minimal effects on higher animals, but ultimately, we will have to study the effects of feeding the resistant plants on animal growth and development,” Dhekney says.

Pollination mechanisms will be another factor to consider if weevil-resistant alfalfa becomes a reality. Organic alfalfa is common in Wyoming and growers may be concerned about genetic contamination of organic crops.

“How far does the pollen of a modified plant blow away? What are the agents of pollen dispersal? What are the effects on beneficial insects that might feed on the pollen?” he asks. “There will be more questions if we come up with a solution for the weevil.”

Potential benefits

Success in creating weevil-resistant alfalfa could be one more tool in an integrated pest management strategy, adding to the effectiveness of other biological or chemical control methods, he adds.

Resistant varieties could also reduce the use of other pesticides that are currently being used to manage weevils in Wyoming.

At one of the large ranches in Sheridan County, Dhekney comments, “They spend thousands of dollars each year on aerial spraying of pesticides for weevils. It would take time, but if we had a variety that was resistant to the weevil, it would essentially mean less spraying, less labor and less use of the plane. This is one strategy that could significantly bring down costs of production.”

The current project is funded for three years of research, with support from the Wyoming Department of Agriculture and the University of Wyoming Agricultural Experiment Station.

“If results look encouraging, we might write a grant for a bigger agency and expand the work. We just have to see what kind of results we get and how quickly, and then we’ll go from there,” notes Dhekney.

Natasha Wheeler is editor of the Wyoming Livestock Roundup and can be contacted at

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