Biology · genetics
The genome and genetics of the sunflower
Thirty-four chromosomes, a genome of 3.6 billion base pairs decoded in 2017, and a DNA that is three-quarters made of jumping elements.
In short: The cultivated sunflower has 34 chromosomes (2n = 34). The reference genome (HanXRQ) was published in 2017 by Badouin et al. in Nature: about 3.6 gigabases and around 52,000 protein-coding genes, of which roughly 75% is transposable elements (jumping DNA). That genome enables targeted breeding for oil content, drought tolerance and disease resistance.
Thirty-four chromosomes
The cultivated sunflower, Helianthus annuus, is diploid and carries 34 chromosomes: 2n = 34, that is seventeen pairs. The number is stable within the species and forms the basis for the classical crossing genetics breeders have used for over a century to make new cultivars. Together the seventeen pairs hold all the hereditary information that steers the plant from seed to flowering head.
Many of the visible traits other pages cover — the spiral arrangement of the disc florets, the posture of the head, the build of the inflorescence — are ultimately fixed in the genes. For those phenomena themselves see the pages on Fibonacci and the golden angle and on heliotropism. The wider overview is in the biology of the sunflower.
The genome, decoded in 2017
For a long time the sunflower genome was considered awkward: large and full of repeats. In 2017 Badouin and colleagues published the first high-quality reference genome of the inbred line HanXRQ in Nature, a project led from INRA and the Université de Toulouse. The genome runs to about 3.6 gigabases — a little larger than the human one — and contains an estimated 52,000 protein-coding genes.
The most striking feature is its makeup: roughly 75% of the DNA is transposable elements, "jumping" sequences that multiplied and spread through the genome over evolutionary time. That abundance of repeats made assembly technically hard and partly explains why the genome is so large. Badouin et al. (2017) also used the genome to unravel the evolution of flowering time and oil production, traits of direct economic importance.
| Feature | Value |
|---|---|
| Chromosomes | 2n = 34 (17 pairs) |
| Genome size | ~3.6 gigabases |
| Protein-coding genes | ~52,000 |
| Transposable-element share | ~75% |
| Reference line | HanXRQ (inbred line) |
| Year of publication | 2017 |
What breeders gain from it
A reference genome is no academic curiosity; it is a tool. With the complete gene map, breeders can apply marker-assisted selection: instead of raising plants for years and waiting, they detect in seedlings the DNA markers linked to desired traits. Badouin et al. (2017) pointed above all to oil content and oil composition, drought tolerance, and resistance to diseases such as fungi and the parasitic weed broomrape.
That application connects to the domestication story: the wild ancestor is heavily branched with many small heads, while the modern plant has been selected for one large head and high oil content. The path from wild to cultivated continues at the species and cultivars; the practical side of sowing and harvesting is at growing sunflowers. Where in the plant the seed — and thus the oil — actually forms is on the anatomy of the flower head.
Sources
- Badouin, H. et al. (2017). The sunflower genome provides insights into oil metabolism, flowering and asterid evolution. Nature, 546, 148–152 (HanXRQ reference genome; INRA / Université de Toulouse).
- Encyclopaedia Britannica — entry "Helianthus annuus / common sunflower" (accessed 2026).