Modern roses at risk from lack of genetic diversity

Intensive, 19th century breeding of roses has led to a reduction in genetic diversity that makes them more vulnerable to diseases and climate change

Hybrid tea rose red colour

Ever admired, roses have been cultivated throughout the ages. In the 1800s there were reportedly, less than 100 varieties, but due to ever increasing breeding by the 1900s that increased to 8000, to today where there are as 35,000.

Research by the evolutionary biologist, Thibault Leroy of the University of Angers in France found that successful commercial varieties, such as hybrid tea roses, have seen more than a quarter of their genetic diversity eroded. The research into their genetic ancestry, revealed that Hybrid tea roses are now heavily skewed to Asian genetic ancestry, with only a quarter of their genes coming from ancient European varieties. Considering that old European roses are more robust than Asian roses, the researchers concluded that this loss of diversity could pose a real risk if climate change or disease threatens the industry.

The research, conducted to retrace the history of rose breeding in Europe and to shed new light on genetic changes during this period, involved collecting large phenotypic and genetic data from 204 accessions, including botanical roses and varieties bred between 1800 and 1910. The researchers also used whole-genome sequences from 32 accessions as an extra resource.

The vulnerability of the roses can be mitigated however, explained Leroy 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. Sadly, more often than not, safeguarding ancient roses comes with numerous challenges such as changes in ownership, passing fads, emerging pathogens and so forth, posing multiple threats to their survival.

According his article on this subject for the New Scientist, James Woodford writes that the plant pathologist, Brett Summerell of the Botanic Gardens of Sydney in Australia, confirmed that organisations such as the Sydney Botanic gardens maintain collections that preserve species purity and older cultivars. In the article, Summerell explained that the preservation of genetic diversity is crucial for the ornamental rose industry and that careful breeding would reduce the enormous quantities of pesticides required to breed them.

Thanks to this study, the researchers have generated the largest GWAS (genome-wide association studies) catalog for roses to date, which can be used as a tool for future rose breeding programs.