Tulip Breaking Virus - History

History

Long thought to be the earliest recorded plant virus, it is now thought that TBV comes second; the earliest reference to a virus-induced leaf chlorosis (possibly Tobacco leaf curl virus) was recorded in Japan in 752 AD.

"Breaking" symptomology was first described in 1576 by Carolus Clusius, a Flemish professor of Botany at Leiden, who noted the variegation, or "rectification", so termed because it was believed that with the offset production of an entirely new "broken" bloom the plant was distilling, or rectifying, itself into a pure life form.

Clusius's observations continued; in 1585, he was the first to note that "broken" plants also slowly degenerated. "…any tulip thus changing its original colour is usually ruined afterwards and so wanted only to delight its master’s eyes with this variety of colours before dying, as if to bid him a last farewell." It was not known that the virus was responsible for this effect, so for centuries breeders believed that it was environmental conditions that attenuated the bulb and caused single colour tulips to break and streak. They tried to induce "rectification" through frequent soil changes (which causing the bulb to go to seed); varying the planting depths so the plant had to struggle in too much or too little soil; applying too much or too little manure; using soil that was either too poor or too rich; or storing the bulbs in exposed conditions so that they would be 'acted' upon by the rain, wind, sun, and extremes of temperature. However, as early as 1637 Dutch growers were able to produced new broken varieties through bulb grafting, by combining "broken" bulbs infected with the virus with healthy bulbs that produced uniformly colored flowers.

At the end of the eighteenth century, the notion that "breaking" in tulips was a manifestation of some kind of chronic disorder or weakness in the bulb was certainly considered among botanists; but it was still more or less understood that adverse environmental conditions were to blame. A comment by William Hanbury in 1770 that: "All variegations are diseases in a plant and nothing is so proper to bring this about as a defect in nutriment." bears out this general attitude. Given the lack of knowledge of human infectious diseases at this time (and well into the 19th century) this was not an unusual conclusion, but what is surprising is that while tulip mosaic disease has a far more impressive and documented history than any other plant virus, the realization that it was a communicable plant disease, let alone a virus, came surprisingly late – a decade after the end of World War I. "Plant virus" to plant pathologists at the time was almost synonymous with the tobacco mosaic virus which had been discovered in 1897, quite soon after bacteriology had become established as an academic subject. Since the prime characteristics of the tobacco mosaic virus are that it damages the leaves and flowers of the plant, stunts growth, and lowers quantity and quality of the crop, it is puzzling to many academics and scientists that twenty more years passed before "breaking" was even suspected of being virus-induced.