Fabled Silk Road could be the route to more flavorful apples

Cornell University
Hybridizations with wild species have made the apple genome very complex and difficult to study - until now.

ITHACA, N.Y. – Cornell University researchers found that the apple’s unique domestication history has led to untapped sources of genes that could be used to improve the fruit’s size, flavor, sweetness and texture.

The Silk Road – the 4,000-mile stretch between China and western Europe where trade flourished from the second century B.C. to the 14th century A.D. – is responsible for one of our favorite and most valuable fruits: the domesticated apple.

Snack-packing travelers would pick apples at one spot, eat them and toss their cores many miles away. The seeds grew into trees in their new locations, cross-bred with the wild species and created the more than 7,000 varieties of apples that exist today.

Hybridizations with wild species have made the apple genome very complex and difficult to study, but a team of multi-disciplinary researchers – co-led by Zhangjun Fei, faculty member at the Boyce Thompson Institute, and Gan-Yuan Zhong, a scientist with the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) in Geneva, New York – tackled this problem by applying cutting-edge sequencing technologies and bioinformatics algorithms to assemble complete sets of both chromosomes for the domesticated apple and its two main wild progenitors.

“Plant breeders could use this detailed information to improve upon traits that matter most to consumers, which today is primarily flavor,” said Fei, also an adjunct associate professor in the College of Agriculture and Life Sciences.

“Perhaps more importantly,” he said, “the information will help breeders produce apples that are more resistant to stress and disease.”

The researchers sequenced, assembled and compared the full reference genomes for three apple species: Gala, a top commercial cultivar of Malus domestica; and apple’s two main wild progenitors – the European crabapple (M. sylvestris) and the central Asian wild apple (M. sieversii), which together account for about 90% of the domesticated apple’s genome.

The results provide apple breeders with detailed genomic roadmaps that could help them build a better apple.

“We wanted to develop new genomes, especially the wild progenitors, because of the tremendous impact they could have on understanding apple’s genetic diversity and identifying useful traits for breeding new cultivars,” said Zhong.

The team’s research is described in a paper published Nov. 2 in Nature Genetics, with authors from BTI, Cornell, the USDA and Shandong Academy of Agricultural Sciences.

The research was supported by the USDA-ARS and by the National Science Foundation.