Slow-darkening pinto beans (IMAGE) American Society of Agronomy Caption Dry beans are a vital source of protein worldwide. Researchers used crop breeding to develop a new variety of pinto bean that darkens slower than the traditional pinto bean, which is desirable for consumers. Credit Juan Osorno Usage Restrictions For use with this story only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.