Scientists discover why some roses smell sweeter than others - and how to improve the scent

A new pathway in the petals has been discovered which produces a fragrance that could be re-introduced into rose varieties that have lost their smell

Scientists have identified an enzyme known as RhNUDX1 which plays a key role in producing the sweet fragrance of roses

Not all roses smell that sweet but scientists have found out why some smell sweeter than others and in the process have discovered a way of potentially improving the scent of the gardener’s favourite ornamental flower.

A study into the chemistry of rose scents has found a new biochemical pathway in the petals of the plants which produces a sweet-smelling fragrance that could be re-introduced into rose varieties that have lost their smell.

Scientists have identified an enzyme known as RhNUDX1 which plays a key role in producing the sweet fragrance of roses, which they suggest could be re-introduced into modern varieties that have lost their scent as a result of intensive breeding for better colour and shape.

Jean-Louis Magnard and colleagues from the University of Lyon in St Etienne in France identified the new source of rose scent in a study published in the journal Science that investigated the source of the strong scent in the rose Papa Meilland.

They found that the enzyme was lacking in another rose, called Rogue Meilland, which produces little scent and a genetic analysis revealed key differences in the genes responsible for the biochemical pathway that led to the synthesis of the enzyme.

The researchers found that the RhNUDX1 enzyme, which works in the cells of the flower petals, generates the well-known fragrance substance called monoterpene geraniol, the primary constituent of rose oil.

In the future, it might be possible to exploit the knowledge about the gene for RhNUDX1 in order to breed pleasant-smelling scents back into modern varieties that lack a strong fragrance, they said.

Scientists believe that the discovery of a new biochemical pathway that can synthesise rose scents is probably due to the independent evolution of chemical attractants designed to advertise flowers and bring pollinators to fertilise them.

It is known that a single constituent of rose oil, such as rose oxide, can impart different scents depending on which 3-D shape they have formed. Rose oxide, for instance, can produce four different scents, sweet, fruity, minty or citrusy, depending on which one of four 3-D shapes it has formed.