For centuries, the idea of a blue rose has captivated imaginations, often symbolizing the unattainable or mysterious. True blue roses, however, do not naturally exist. Despite this, human ingenuity has led to the development of “blue-ish” varieties, primarily through genetic engineering.
Why Natural Blue Roses Are Rare
Roses naturally produce a range of vibrant colors such as red, pink, yellow, and white, but a true blue hue has remained elusive in their natural palette. This is due to a specific genetic absence within the rose plant. Roses lack the gene that codes for the enzyme flavonoid 3′,5′-hydroxylase (F3’5’H). This enzyme is essential for synthesizing delphinidin, the blue pigment commonly found in other flowers like petunias and delphiniums.
Instead of delphinidin, rose coloration is primarily determined by other anthocyanin pigments like cyanidin and pelargonidin, along with carotenoids. These pigments produce shades ranging from red and pink to orange and yellow. The absence of the F3’5’H enzyme means that roses cannot complete the biochemical pathway necessary to produce the blue pigment, confining their natural colors to the warmer spectrum or white.
Early Attempts to Create Blue Roses
Before modern genetic tools, the desire for blue roses led to various traditional approaches, none of which yielded a genuinely blue flower. Breeders attempted conventional hybridization, crossing different rose varieties. These efforts consistently resulted in roses with purplish or lilac tones, such as ‘Blue Moon’, rather than a pure blue, because the fundamental genetic component for blue pigment was not present in the rose gene pool.
Artificial methods also became common to satisfy the demand for blue roses. The most widespread technique involved dyeing white roses blue. This process typically involves placing cut white rose stems into water mixed with blue dye, allowing the dye to be absorbed into the petals. While these dyed roses offer a blue appearance, their artificial nature and often uneven coloration are distinct from a naturally occurring blue, and the color is temporary.
The Breakthrough of Genetic Engineering
The quest for a blue rose saw a breakthrough with genetic engineering. Japanese company Suntory partnered with Australian firm Florigene in a nearly two-decade collaborative effort. Their research, which began in 1990, focused on introducing the missing genetic pathway into roses.
Scientists identified and isolated the gene responsible for delphinidin production from a pansy. This gene was then introduced into rose plants using Agrobacterium-mediated transformation, a common method for inserting foreign DNA into plant cells. To enhance the blue hue, they also employed RNA interference (RNAi) technology to suppress the rose’s native dihydroflavonol 4-reductase (DFR) gene, which is involved in producing red pigments. This dual approach aimed to both introduce blue pigment and reduce competing red pigments. The development was announced in 2004, and the first genetically engineered “blue” roses, named ‘SUNTORY blue rose APPLAUSE’, were commercially launched in 2009.
What “Blue” Really Means for Roses
Despite the genetic engineering breakthrough, “blue” roses available do not exhibit a vibrant, pure blue color like that of a cornflower or delphinium. Genetically engineered roses, such as ‘Applause’, are more accurately described as lavender, mauve, or purplish-blue. This is due to several factors influencing pigment expression within the rose petals.
One reason is the acidity of rose petals. The pH level within the cellular vacuoles of rose petals affects how the delphinidin pigment appears. Delphinidin tends to appear bluer in neutral or weakly acidic environments, but in the more acidic conditions of rose petals, its color shifts towards the red or purple spectrum. Additionally, RNAi technology did not completely eliminate the production of the rose’s native red pigments, leading to a mixed coloration. Scientists continue to research ways to achieve a purer blue by further modifying the rose’s internal chemistry, including adjusting petal pH and improving pigment accumulation.