Yang Bai (Ph.D. Horticulture ’14), post-doctoral scientist at the Boyce Thompson Institute (BTI) is first author of the Nature Communications journal article Genome re-sequencing reveals the history of apple and supports a two-stage model for fruit enlargement featured in this BIT News article by Alexa Schmitz. Bai’s research was also featured in The Guardian.
Centuries ago, the ancient networks of the Silk Road facilitated a political and economic openness between the nations of Eurasia. But this network also opened pathways for genetic exchange that shaped one of the world’s most popular fruits: the apple. As travelers journeyed east and west along the Silk Road, trading their goods and ideas, they brought with them hitchhiking apple seeds, discarded from the choicest fruit they pulled from wild trees. This early selection would eventually lead to the 7,500 varieties of apple that exist today.
Researchers at Boyce Thompson Institute (BTI) have been working hard to excavate the mysteries of the apple’s evolutionary history, and a new publication this week in Nature Communications reveals surprising insights into the genetic exchange that brought us today’s modern, domesticated apple, Malus domestica.
In collaboration with scientists from Cornell University and Shandong Agricultural University in China, the researchers sequenced and compared the genomes of 117 diverse apple accessions, including M. domestica and 23 wild species from North America, Europe, and East and central Asia.
A tale of two roads
The most exciting outcome of this genomic comparison is a comprehensive map of the apple’s evolutionary history. Previous studies have shown that the common apple, Malus domestica arose from the central Asian wild apple, Malus sieversii, with contributions from crabapples along the Silk Road as it was brought west to Europe.
With the results of this new study, the researchers could zoom in on the map for better resolution. “We narrowed down the origin of domesticated apple from very broad central Asia to Kazakhstan area west of Tian Shan Mountain,” explained Zhangjun Fei, BTI professor and lead author of this study.
In addition to pinpointing the western apple’s origin, the authors were excited to discover that the first domesticated apple had also traveled to the east, hybridizing with local wild apples along the way, yielding the ancestors of soft, dessert apples cultivated in China today.
“We pointed out two major evolutionary routes, west and east, along the Silk Road, revealing fruit quality changes in every step along the way,” summarized Fei.
Although wild M. sieversii grows east of Tian Shan Mountain, in the Xinjiang region of China, the ecotype there was never cultivated, and did not contribute to the eastern domesticated hybrid. Instead, it has remained isolated all these centuries, maintaining a pool of diversity yet untapped by human selection. First-author Yang Bai remarked, “it is a hidden jewel for apple breeders to explore further.”
