Researchers have produced a chromosome-level genome assembly for a sweetpotato cultivar called ‘Tanzania.’
‘Tanzania’ sweetpotato variety. Image credit: Benard Yada, National Crops Resources Research Institute in Uganda.
The sweetpotato is a globally important stable crop that feeds millions worldwide, especially in sub-Saharan Africa, where its natural resilience to climate extremes makes it crucial for food security.
But this humble root vegetable has guarded its genetic secrets for decades.
Sweetpotato DNA is extraordinarily complex. While humans have two sets of chromosomes, one from each parent, sweetpotatoes have six.
This condition, called hexaploidy, made deciphering their genetic code like trying to reconstruct six different, yet similar, sets of encyclopedias that have been shuffled together.
Using cutting-edge DNA sequencing, along with other advanced techniques, Boyce Thompson Institute’s Professor Zhangjun Fei and colleagues created the first complete genetic makeup of ‘Tanzania,’ a sweetpotato variety prized in Africa for its disease resistance and high dry matter content.
The central challenge was to untangle the plant’s 90 chromosomes and organize them into their six original sets, called haplotypes.
The researchers succeeded in fully separating, or phasing, this complex genetic puzzle, something that had never been achieved before.
“Having this complete, phased genome gives us an unprecedented level of clarity,” Professor Fei said.
“It allows us to read the sweetpotato’s genetic story with incredible detail.”
According to the team, the sweetpotato genome is a mosaic assembled from multiple wild ancestors, some of which have yet to be identified.
About one-third comes from Ipomoea aequatoriensis, a wild species found in Ecuador that appears to be a direct descendant of a sweetpotato progenitor.
Another significant portion resembles a wild Central American species called Ipomoea batatas 4x, though the actual donor may still remain undiscovered in the wild.
“Unlike what we see in wheat, where ancestral contributions can be found in distinct genome sections,” said Dr. Shan Wu, a researcher at the Boyce Thompson Institute.
“In sweetpotato, the ancestral sequences are intertwined on the same chromosomes, creating a unique genomic architecture.”
This intertwined genetic heritage means that sweetpotato can be tentatively classified as a segmental allopolyploid — essentially a hybrid that arose from different species but behaves genetically as if it came from a single one.
This genomic merging and recombination gives sweetpotato its remarkable adaptability and disease resistance, traits crucial for subsistence farmers worldwide.
“The sweetpotato’s six sets of chromosomes also contribute to its enhanced resilience,” Professor Fei said.
“With multiple versions of important genes, the plant can maintain backup copies that help it survive drought, resist pests, and adapt to different environments — a feature known as polyploid buffering.”
“However, achieving a full understanding of sweetpotato’s genetic potential will require decoding multiple varieties from different regions, as each may carry unique genetic features that have been lost in others.”
The findings were published this month in the journal Nature Plants.
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S. Wu et al. Phased chromosome-level assembly provides insight into the genome architecture of hexaploid sweetpotato. Nat. Plants, published online August 8, 2025; doi: 10.1038/s41477-025-02079-6