All Arabica Coffee Is Genetically Similar: How Can Beans Taste So Different?
A study has found that the differences in flavor notes and other characteristics of coffee varieties from around the world are not due to variations in individual genes but rather the result of wholesale swapping, deletion, and rearrangement of chromosomes. The most complete sequencing yet of the genome of Coffea arabica has revealed that the ‘letters’ in the DNA strands differ only slightly between varieties. Michele Morgante, a plant geneticist at the University of Udine, Italy, and his team used next-generation sequencing technology that can read DNA strands up to hundreds of thousands of base pairs in length without interruption and with greater accuracy than earlier technologies.
Coffee’s genetic make-up is no trivial concern; 10 million tonnes of the crop were grown and sold in 2022–23. The coffee that we drink comes from two species: Coffea canephora, also known as robusta, and Coffea arabica, known as arabica. In many cases, beans from the two species are blended to make a brew. However, the beans of single species are also roasted and sold. Overall, arabica beans represent around 56% of all coffee sold.
Most genetic variation in living organisms comes from hybridization with other species. However, for C. arabica, this is a relatively rare event because it has more than two copies of each chromosome — a phenomenon called polyploidy. As a result, C. arabica’s main source of single nucleotide variation is mutation, which occurs at a steady rate over time. The study found evidence of significant chromosomal rearrangements, especially in a varietal of C. arabica called Bourbon.
The sequenced genome will be a valuable resource for coffee breeders, particularly as disease and climate change challenge the long-term sustainability of coffee. Getting a proper in-depth understanding of the genome would help us understand how the crop evolved and the genomes of coffee in line with its parents. The work will also inform coffee breeding programs and possibly even genetic modification to select for favourable characteristics, such as resistance to a fungus called coffee rust or low caffeine levels.
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