The origins and adaptation of European potatoes reconstructed from herbarium genomes

Potato, the third most important staple crop, originates from the highlands of the equatorial Andes. There, potatoes propagate vegetatively via tubers under short days, constant throughout the year. After their introduction to Europe in the 16th century, potatoes adapted to a shorter growing season and to tuber formation under long days. Here, we traced the demographic and adaptive history of potato introduction to Europe. To this end, we sequenced 88 individuals that comprise landraces, modern cultivars and historical herbarium samples, including specimens collected by Darwin during the voyage of the Beagle. Our findings show that 17th-century European potatoes were closely related to Andean landraces. After their introduction to Europe, potatoes admixed with Chilean genotypes. We identified candidate genes putatively involved in long-day pre-adaptation, and showed that 17th century European individuals were not long-day adapted through previously described insertions in the CYCLING DOF FACTOR1 (CDF1) gene. Such insertions likely occurred de novo in Europe during the 19th century. Our study highlights the power of combining contemporary and historical genomes to understand the complex evolutionary history of crop adaptation to new environments.