The most prized tulips of the Dutch Golden Age were sick with a virus.
The flamed and feathered tulips that fetched fortunes in 17th-century Holland got their streaks from a virus spread by aphids. It also slowly weakened the bulbs, which is why legendary varieties like Semper Augustus no longer exist. Nobody worked out the cause until the late 1920s.
A 'broken' tulip has lost its single, uniform colour. Instead its petals show intricate bars, streaks, feathers or flames, often with different patterns on each side of a petal. The effect comes from a potyvirus that disrupts the even distribution of anthocyanin pigments in the petal's outer layer, so colour fades in some places and intensifies in others. Such blooms were the most coveted of the 17th-century Dutch tulip craze.
The Flemish botanist Carolus Clusius described breaking in 1576, and by 1585 had noticed that broken plants slowly degenerated. A tulip that changed colour this way, he wrote, seemed to want only to delight its owner's eyes before bidding him a last farewell. The virus stunts the bulb and its offsets generation by generation, until the line can no longer flower and dies out. That is why the most celebrated broken tulips, Semper Augustus and Viceroy, are lost.
For centuries growers blamed the environment and tried to provoke breaking by starving or overfeeding bulbs, changing their soil or planting depth, or leaving them exposed to the weather. Yet by 1637 Dutch growers could make new broken varieties by grafting infected bulbs onto healthy ones: they were spreading a disease without knowing it. Even after tobacco mosaic virus was discovered in 1897, it took decades before anyone suspected tulips.
The answer came from Dorothy Cayley at the John Innes Horticultural Institution in London. From 1928 she transferred tissue from broken bulbs into healthy ones and showed that the breaking passed with it, in proportion to the amount introduced, and was probably carried by insects. Aphids, especially the peach-potato aphid, were later confirmed as carriers. Many countries now ban the sale of infected bulbs. Today's striped tulips, such as 'Rem's Sensation', owe their pattern to breeding, not infection, though connoisseurs say they fall short of the lost originals.
Source: Wikipedia — Tulip breaking virus · Text summarised from Wikipedia (CC BY-SA 4.0)
