They trace the origin of Arabica coffee to Ethiopia 600,000 years ago

April 15 () –

Scientists have sequenced the highest quality reference genome so far of the most popular coffee variety, arabica, revealing secrets of his lineagespanning millennia and continents.

His findings, published in Nature Genetics, suggest that Coffea arabica developed more than 600,000 years ago in the forests of Ethiopia through natural crossing between two other coffee species. The study found that the arabica population rose and fell during periods of Earth's warming and cooling for thousands of years, before being cultivated in Ethiopia and Yemen, and then spread throughout the world.

“We have used genomic information from plants alive today to go back in time and paint the most accurate picture possible of the long history of arabica, as well as to determine how modern cultivated varieties are related to each other,” says the study's corresponding co-author Victor Albert, a professor in the Department of Biological Sciences at the University at Buffalo, in a statement.

Coffee giants like Starbucks and Tim Hortons exclusively use beans from Arabica plants to brew the millions of cups of coffee they serve every day; However, partly due to low genetic diversity stemming from a history of inbreeding and small population size, Arabica is susceptible to many pests and diseases and can only be grown in a few places in the world where pathogen threats are lower and climatic conditions are more favorable.

“A detailed understanding of the origins and breeding history of contemporary varieties is crucial to developing new Arabica cultivars better adapted to climate change,” says Albert it's a statement.

From their new reference genome, achieved using cutting-edge DNA sequencing technology and advanced data science, the team was able to sequence 39 varieties of Arabica and even an 18th-century specimen used by Swedish naturalist Carl Linnaeus to name the species. .

The reference genome is now available in a publicly available digital database.

“Although there are other public references on Arabica coffee, the quality of our team's work is extremely high,” says one of the study's co-leaders, Patrick Descombes, senior genomics expert at Nestlé Research. “We use next-generation genomic approaches, including long- and short-read high-throughput DNA sequencing, to create the most advanced, complete and continuous Arabica reference genome to date.”

Arabica is the source of approximately 60% of the world's total coffee products, and its seeds help millions of people start their day or stay up late. However, the initial crossing that created it was done without any human intervention.

Arabica was formed as a natural hybridization between Coffea canephora and Coffea eugenioides, where it received two sets of chromosomes from each parent. Scientists have had difficulty determining exactly when and where this allopolyploidization event took place, with estimates ranging from 10,000 to 1 million years ago.

To find evidence of the original event, the UB researchers and their partners ran their various arabica genomes through a computational modeling program to look for signatures of the species' basis.

The models show three demographic bottlenecks during the history of Arabica; the oldest occurred about 29,000 generations (or 610,000 years) ago. This suggests that Arabica formed sometime earlier, between 610,000 and 1 million years ago, the researchers say.

“In other words, the crossbreeding that created Arabica was not something humans did,” Albert says. “It's pretty clear that this polyploidy event predates modern humans and coffee cultivation.”

Coffee plants were long thought to have developed in Ethiopia, but the varieties the team collected around the Great Rift Valley, which stretches from southeast Africa to Asia, showed a clear geographical division. All wild varieties studied originated on the western side, while all cultivated varieties originated on the eastern side, closer to the Bab al-Mandab Strait separating Africa and Yemen.

This would coincide with evidence that coffee cultivation may have begun primarily in Yemen, around the 15th century. Indian monk Baba Budan is believed to have smuggled the legendary “seven seeds” out of Yemen around 1600, establishing Indian Arabica crops and setting the stage for coffee's global reach today.

“It seems that the diversity of Yemeni coffee may be the founder of all the main current varieties” says Descombes. “Coffee is not a crop that has been heavily crossed, like corn or wheat, to create new varieties. People mainly chose a variety they liked and then grew it. “So the varieties we have today have probably been around for a long time.”