||Helianthus annuus, the common sunflower, is an annual, branched sunflower species, the wild progenitor of cultivated sunflower (also H. annuus). Native to North America, its natural range spans from Northern Mexico to Southern Canada. Generally found of mesic, disturbed soils, populations of H. annuus have adapted to a variety of extreme conditions (high salinity, drought, low nutrients, flooding...). Together with other wild sunflower species, it is a long-standing model system for speciation, adaptation, ecotype formation and domestication studies, and, more recently, genomic studies. Wild sunflowers have also contributed numerous useful alleles to the cultivated sunflower gene pool.
H. annuus is diploid and has a relatively large (3.5 Gbp), extremely repetitive genome (TE represent >75% of the genome), organized in 17 chromosomes. Numerous large chromosomal rearrangements and structural variants distinguish its genome from that of other wild sunflowers, and of cultivated sunflower.