Modern commercial roses have lost over a quarter of their genetic diversity compared with older varieties, which could leave them vulnerable to diseases or climate change.
Roses have been admired and grown since antiquity, when people in Asia and Europe began cultivating ancient varieties from a dozen wild rose species. There were less than 100 varieties before 1800, but by 1900 there were around 8000 varieties of crossed Asian and European roses. Now, there are as many as 35,000.
To reconstruct the genetic history of roses, at the University of Angers, France, and his colleagues sequenced 15 varieties, including ancient European and ancient Asian cultivars, early Asian-European hybrids and hybrid tea roses.
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By combining the results with genetic studies of 17 other publicly available varieties, the researchers amassed a dataset comprising the whole genomes of 32 roses. They also looked at data on tens of thousands of genetic markers in more than 200 rose varieties.
鈥淪urprisingly, and despite the limited number of individuals included in the study, we observed that most individuals exhibit family relationships with other varieties, suggesting that rose breeding in the 19th century was based on a very limited number of generations of breeding, less than 10,鈥� says Leroy.
The study found that massively successful commercial varieties, such as hybrid tea roses, are now heavily skewed to an Asian genetic ancestry 鈥� only a quarter of their genes are from ancient European varieties. This could make them vulnerable to extreme weather events, says team member , also at the University of Angers. 鈥淚t is generally considered that old European roses are more robust than Asian roses.鈥�
In these modern hybrids, more than a quarter of all genetic diversity seen in ancient cultivars has been eroded. This loss of diversity could be an issue if climate change or disease threatens the industry.
However, Leroy says this risk can be mitigated as long as collectors and botanic gardens around the world conserve their extensive collections of ancient roses, as these varieties still hold a full suite of genetic diversity.
鈥淯nfortunately, challenges such as changes in ownership of the rose collections, passing fads, climate change, emerging pathogens, etc. pose diverse threats to the safeguarding of these ancient rose collections,鈥� says Leroy.
at the Botanic Gardens of Sydney in Australia says organisations such as his maintain collections that preserve species purity and older cultivars.
One reason why preserving genetic diversity is important is that the ornamental rose industry uses enormous quantities of pesticides, and careful breeding could reduce this, says Summerell. 鈥淲e need to breed more sustainable roses, in term of using less chemicals.鈥�
bioRxiv
