Crop breeding

Old beans may have new uses

In the United States, you will be hard pressed to find a barbeque without baked beans. Green bean casserole is a Thanksgiving favorite. Refried beans come on the side of our orders at Mexican-American restaurants. And who can turn away from pasta e fagioli?

In fact, beans are the highlight of many dishes across the world. In some cases, beans are the primary protein or iron source in a community’s diet. These bean dishes are all from one species: Phaseolus vulgaris.

Beans were first domesticated around 8,000 years ago in Central and South America. During this time, humans shifted their focus to breeding bigger beans that are tastier and easier to harvest.

cranberry bean dish in a bowl
A cranberry bean dish ready to be enjoyed. Credit: Miranda J. Haus

One problem that has been hard for breeders to overcome is reducing yield loss due to fungal root pathogens. One of these is Fusarium Root Rot and Fusarium Wilt. In some instances, Fusarium root rot can cause a farmer to lose their entire crop.

Every crop we eat was once growing in the wild, undisturbed. These versions of crops are called Crop Wild Relatives. Over the last 10,000 years humans domesticated food crops to make them easier to grow, harvest and even more nutritious. During domestication, humans only took select individuals from the entire population and began to grow and cultivate plants from this subset of seeds.

By selecting the best-tasting or highest-yielding beans, farmers inadvertently reduced the genetic diversity. This doesn’t just apply to beans it applies to all crop species. As an example, let’s think about aliens to coming to Earth and abducting the population of a small town to populate a new planet. Any small town in the world cannot represent the genetic diversity of our entire planet! So, you can see the new planet would suffer from reduced genetic diversity. That’s what has happened with crop diversity during domestication.

Back to our beans, we have two different groups of Phaseolus vulgaris: those we grow to eat (cultivated) and those that remain in the wild. The wild group has retained more genetic diversity and may exhibit resistance to Fusarium root rot, a feature not present in cultivated beans.

side by side photos of a healthy and unhealthy bean roots
The left image shows a healthy bean root system, while the right image shows a young root system infected with Fusarium Root Rot. Fusarium Root Rot causes root necrosis, discoloration, and stunting. Credit: Miranda J. Haus

For this reason, our team evaluated all the available wild beans in the United States Department of Agriculture’s Germplasm Resource Information Network. The USDA maintains genebanks throughout the United States. that contain collections of seeds from all over the world. These collections are freely available to anyone, and the USDA works closely with researchers to create catalogs of traits for the seeds within their collections.

We evaluated the USDA wild bean collection to see if we could find wild beans that might be resistant to Fusarium Wilt. We infected seedlings with two pathogens which cause Fusarium Wilt and Fusarium Root Rot. We rated the wild beans, specifically looking for those that did not show symptoms of either disease.

From the entire collection of 248 wild bean lines, we found twenty-one lines with resistance to Fusarium Root Rot and sixteen lines with resistant to Fusarium Wilt. We are attempting to crossbreed some of the resistant wild beans with cultivated beans, to see if the new beans will also be resistant to Fusarium. We have also made our information freely available so other breeders can start introducing resistance into their lines as well in our paper published in Crop Science Journal.

As you can see with our research, while wild beans might not be tasty or fast-cooking, they do have important potential for improving the food we eat every day.

Be sure to check out Crop Science Society of America’s Crop Wild Relative page for a collection of blogs, news stories and a video about the use of crop wild relatives in potato breeding! Answered by Miranda J. Haus, Michigan State University

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

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