At first glance, the humble sweet potato seems anything but complicated. It’s a culinary staple, wrapped in holiday nostalgia and plenty of mini marshmallows. But behind its earthy simplicity there lies a genome so intricate that it has taken scientists decades to decipher. Now, a newly published study in Nature Plants has finally cracked the code.
Spoiler alert: This is not your average root vegetable. It’s a genetic powerhouse with six sets of chromosomes and a tangled evolutionary past.
Most familiar crops are diploid, with two copies of each chromosome: one from each parent. But it seems that sweet potatoes are overachievers. As a hexaploid, Ipomoea batatas carries six copies of each chromosome, the result of multiple rounds of whole-genome duplication and hybridization events throughout its evolutionary history.
This genetic redundancy isn’t accidental. It has significant implications for how the plant grows, stores nutrients, and expresses traits, especially when it comes to its iconic (delicious) swollen storage roots.
Image by Alexander Knyazhinsky, Shutterstock
With the help of techniques like long-read sequencing and high-throughput chromosome conformation capture (Hi-C), researchers were able to generate the first phased, chromosome-level assembly of the sweet potato genome. That means not only do we now have the full blueprint, but we have all six sets of instructions neatly separated, like six color-coded copies of a very complicated recipe.
This is a major leap forward in understanding sweet potato biology. Previous genome assemblies were highly fragmented and couldn’t resolve the differences between the chromosomes sets. Now, scientists can distinguish how different gene copies vary in sequence, expression, and function.
One of the study’s key focuses was on the molecular underpinnings of storage root formation, arguably the sweet potato’s most defining trait. By comparing gene expression across different tissues and developmental stages, the researchers identified a suite of genes involved in starch biosynthesis, root thickening, and hormonal regulation.
More interestingly, they found subgenome bias, certain chromosome sets being more active than others in regulating storage root development. This suggests that the sweet potato’s evolutionary history hasn’t just duplicated genes; it’s also fine-tuned which ones get to do the heavy lifting.
The study goes beyond answering nerdy genetic questions and has real implications for crop improvement. With a clearer picture of which genes are most involved in root development, breeders can more precisely target traits like yield, nutrient density, and stress tolerance. It also paves the way for gene editing and genome-informed breeding strategies that were previously impossible in such a complex organism. Understanding how the sweet potato’s complex genome has been domesticated, and how it continues to function, could also help researchers engineer similar traits in other crops.
The sweet potato has officially entered the genomic big leagues … and we’re just only beginning to tap into what it can teach us.
Some facts about sweet potatoes
The sweet potato is a dicotyledonous vegetable belonging to the family Convolvulaceae. It is the seventh-most produced crop worldwide after wheat, rice, maize, potato, barley, and cassava, and the fifth in developing countries. In the U.S., North Carolina is by far the most prolific producer of sweet potatoes — a status it has held since 1971 — with California and Mississippi coming up in the two spots behind it.
Thanks to high levels of vitamins A and C, as well as abundant supplies of iron, potassium, dietary fiber, sweet potatoes are considered to be the most most nutritious vegetable a person can eat.
The color of this food is linked to its beneficial health effects. Lighter fleshed varieties are reported to have higher levels of phenolic compounds, whereas a more intense yellow color is associated with a higher content of carotenoids, mainly ß-carotene. Additionally, yellow- and orange-fleshed sweet potatoes are rich in phenolic acids, while those varieties that are purple have very high levels of anthocyanins.
The crop, which is used interchangeably with the term “yams” in the U.S., can be purchased fresh, frozen, or canned — and if bought fresh, they can be stored in a cool, dry place for up to one month.
Leah Elson is an American scientist, author, and public science communicator. She has two pit bulls and sixty-eight houseplants.
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