The scent of a rose fades over time, and has for hundreds of years.

For centuries, generations of breeding in the quest for longer blooms and petals in shades of nearly every hue have dulled the sweetest smells that once perfumed gardens around the world.

French researchers have figured out which genes make a rose smell so sweet, and where to tinker in the genome to enhance its scent.

Although the genome has been mapped before, a newly published version is far more complete, indicating which genes tend to travel together — scent and color, for instance — and which genes are responsible for such traits as continuous blooming. The study, published in the journal Nature Genetics, also reveals a detailed family tree of the rose, and how it differs from its closest cousin, the strawberry, and its more distant apple and pear relations.

“It’s a very nice way of putting them all together and showing their history. And I think it’ll be very important for breeding,” said Rob Martienssen, a plant biologist and professor at Cold Spring Harbor Laboratory on Long Island. He said it will be useful for breeding plant species other than the rose, as well.

To develop a new type of rose, breeders typically make thousands of hybrid offspring, looking for the combination of traits they want. It’s a process that can take up to 10 years, said Mohammed Bendahmane, a senior author and research director at the École Normale Supérieure de Lyon, in France. With data from the more detailed genome sequence, this process should be shortened, reducing the cost and energy consumption needed to introduce new species, he said.