Pinto beans

A new variety of slow-darkening pinto beans shows benefits for the entire value chain. Photo submitted by Juan Osorno.

Too often a shopper’s selection of items in the grocery store is based on how the product looks. An item such as pinto beans provides a prime example of the scrutiny some items go through at the local supermarket. They are packed with protein and fiber, as well as a host of micronutrients. But put the nutrition aside somewhat, because pinto beans must look good to the consumer in order to sell.

Pinto beans, which are a big crop throughout the region, have a striking mottled pattern of dark and light brown. However, the beans can turn a darker color after harvest, and this darker color causes some consumers to think the bean is inferior compared to lighter beans and will pass them by on the store shelf.

“We eat with our eyes,” said Juan Osorno, dry edible bean breeder at North Dakota State University, who noted the darker-colored beans also cause some concern for the farmers who grow them. “Farmers see darker pinto bean seeds as being of poorer quality, and when farmers try to sell darker beans, they often have to accept discounted prices.”

In an effort to slow the darkening of pinto beans after harvest, Osorno and his associates have been working on developing varieties that retain the good performance farmers and consumers are looking for, and yet, are slow to darken.

At the root of these difficulties lies pinto bean genetics. Physical characteristics, such as yield, bean size, or rate of darkening, are all affected by one or more genes.

As it turns out, a single gene – aptly named slow darkening or SD – controls how quickly pinto beans darken after harvesting. Researchers can breed this gene into new pinto bean varieties fairly easily without creating a genetically modified organism (GMO). But whenever they’ve incorporated this gene in the past, other genes responsible for lower yields or smaller beans would come along with the slow-darkening gene.

The initial tests on the darkened pinto bean were conducted from 2010-12, and did not have encouraging results, according to Osorno. The slow-darkening beans performed poorly when compared to regular pinto bean varieties. Those early varieties with the show-darkening gene had many issues associated with agronomic performance.

The researchers compared traits such as seed weight, yield, and cooking time between slow-darkening and regular pinto beans.

The “early generation bred” SD pintos had significantly lower emergence, increased lodging, less seed yield and smaller seed size, Osorno noted, when compared to the regular darkening (RD) varieties. The tests between the two varieties were carried out in research plots in North Dakota and Washington.

But the latest round of field trials using slow-darkening pinto beans was more promising. According to the 2018 tests, the newer slow-darkening pinto bean varieties are catching up to regular varieties in yield and bean size. In fact, a second generation of slow-darkening pinto beans is already showing higher yields compared to the previous generation.

Overall, SD pintos exhibited better canning quality than RD pintos, and whether raw or cooked, the SD beans were much lighter in color than RD pintos.

Osorno is encouraged, but says there’s still work to be done. “Remember that breeding yield gains is a stepwise manner rather than through big jumps,” he said.

Breeders should continue to focus on improving agronomic performance for emergence, lodging, seed yield, seed size and canning quality of the new SD pinto beans, according to Osorno.

He believes these slow-darkening pinto beans can be a good alternative for the existing pinto bean value chain. “Both farmers and consumers will benefit from it in many ways,” he said.

For example, the slow-darkening beans cooked faster than regular beans. Needing less time to cook can be a great benefit in areas where cooking fuel is scarce.

This work was funded by Northarvest Bean Growers Association, United States Department of Agriculture National Institute of Food and Agriculture, United States Department of Agriculture Agricultural Marketing Service, and the North Dakota Department of Agriculture.