DNA reveals the origin of East Asia’s favorite sweet bean 

Red adzuki beans are a beloved staple successful East Asia. Cooks tuck a saccharine paste made from them wrong mochi, swirl it into mooncakes and furniture it beneath custard successful taiyaki. But contempt its popularity, which radical were the archetypal to commencement utilizing this legume remained murky — until now. 

Scientists person analyzed the DNA of astir 700 varieties of adzuki crossed Asia. Some of these plants turn successful the wild. People person been farming — oregon cultivating — different types. The beans’ genes now suggest that adzuki was archetypal cultivated successful Japan betwixt 3,000 and 5,000 years ago. Only aboriginal did radical commencement increasing a wide assortment of these reddish beans successful China.  

The probe besides uncovered DNA tweaks, oregon mutations, that gave emergence to the beans’ affluent reddish hue. 

“I was amazed by fundamentally everything,” says Cheng-Ruei Lee. He studies evolutionary genetics astatine National Taiwan University successful Taipei. That tract of subject looks astatine however variations successful DNA pb organisms to evolve caller traits. Lee is portion of a squad that shared its caller findings May 29 in Science. 

History written successful DNA 

Adzuki beans turn successful pods connected bushy plants. They person a people sweet, nutty flavor. Fossils of past beans hinted that Japan’s Jomon radical mightiness person grown adzuki. The Jomon were hunter-gatherers who lived arsenic aboriginal arsenic 16,000 years ago.  

But reddish legume DNA had pointed to a antithetic root story. Beans from China amusement a wider assortment successful their DNA than those successful Japan. Such diverseness is typically lone seen successful plants that radical started to cultivate a precise agelong clip ago. 

Adzuki beans were archetypal domesticated successful Japan 3,000 to 5,000 years ago, a caller DNA investigation shows.keithferrisphoto/Getty Images

The caller DNA investigation helps marque consciousness of these conflicting data.  

A plant’s atomic genome is made up of the DNA tucked wrong the nuclei of its cells. Plants inherit their atomic DNA from some parents. And reddish beans grown successful China bash amusement the astir diverseness successful their atomic genomes, Lee’s squad found.  

But the squad recovered different important hint successful a antithetic root of the bean’s DNA. This DNA is tucked successful structures wrong works cells known arsenic chloroplasts. In reddish beans, lone pistillate plants walk this DNA to their offspring. And this benignant of DNA evolves much slowly. That chloroplast DNA successful Chinese reddish beans intimately matches what’s recovered successful chaotic Japanese beans. 

There’s lone 1 mode that these pieces of grounds tin acceptable together, Lee says. People archetypal started increasing reddish beans successful Japan, and the signifier aboriginal dispersed to China. There, radical cross-bred Japanese reddish beans with local, chaotic Chinese reddish beans.  

Today, Chinese reddish beans present amusement a overmuch wider assortment successful their DNA. But their chloroplasts inactive clasp traces of their past Japanese ancestors.  

Turning red 

Through farming, adzuki beans besides got a makeover. Wild beans are airy with acheronian mottled spots. The farmed varieties are reddish each over.  

Lee’s squad recovered 1 mutation successful beans’ DNA ...