Hardy bean promises solutions for drought

Pinto beans (lower left) and navy beans (lower right) are similar in size to two varieties of tepary bean. | Kristen Bett photo

Researchers are learning more about a remarkable bean that is far better at surviving harsh conditions than its dry bean relatives.

Tepary beans are one of five species of beans that have been domesticated.

Most farmers and consumers are familiar with pintos, blacks and navy beans, which are part of the common bean species.

Tepary beans are grown in borderline desert areas like northern Mexico, the southwestern United States and Africa, said Kirstin Bett, a University of Saskatchewan dry bean breeder and one of a team of researchers trying to figure out what makes the crop hardier than common beans.

“They are very much more tolerant of heat and drought. In fact, they hate water,” she said.

The researchers discovered that when temperatures rise to 27 C at night, which would have devastating consequences for most dry beans, it activates heat stress genes in the tepary bean that protect the plant.

“They are incredibly heat tolerant. Like, the plants don’t even wince when you hit them with 40 degrees (Celsius),” she said.

The bean is well-suited to marginal environments because of its stress tolerance. In fact, it yields better in dryland production than it does under irrigation, which is the exact opposite of common beans.

Bett is more interested in the plant’s cold tolerance than its heat tolerance because that is a bigger issue for bean production on the Canadian Prairies.

It can’t withstand sub-zero temperatures but it does have far better cold tolerance than common beans.

The researchers sequenced the genome of the tepary bean to help determine why the plant is better adapted to temperature extremes than its common bean cousin.

The hope is that researchers can eventually breed those same traits into common beans but that is a complicated process because it involves multiple genes and tepary beans don’t cross very readily with common beans.

Breeders have to backcross a few times to get a plant that is fully fertile, resulting in a few generations of yield loss.

Plus, the tepary bean brings with it a bunch of “baggage” such as poor disease resistance because it is from dry regions of the world where there is less disease pressure.

For now the work is on hold because Bett doesn’t have the funding to explore it any further. She is more focused on expanding her common bean breeding program in anticipation of the expansion of Saskatchewan irrigation districts.

But she intends to continue making some crosses with tepary beans because it could prove to be a useful resource as climate change continues to add more environmental stresses to dry bean production in the prairie region.

Bett is also exploring the possibility of adapting the tepary bean itself so that it would be suitable for growing in Saskatchewan rather than transferring its best traits into common beans.

However, the crop is a long way from being suitable for Saskatchewan. Existing varieties are long-season and have a habit of growing close to the ground, making it difficult to mechanically harvest the crop.

And once again there is a lack of funding to do that kind of long-term breeding work on tepary beans.

But she thinks there could one day be a market for the beans, which have a different flavour profile than regular beans.

Bett believes it could have some appeal with local chefs because it is one of North America’s native foods and is still regularly consumed by indigenous people in northern Mexico and New Mexico.

She thinks it could eventually become a cool little niche crop for growers but in the meantime it is more of a research curiosity.

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