On Wed, 1 Mar 1995, Josh Goldstein wrote:
> Sometime back I came across a reference to tulip break virus. It streaks
> hybrid tulips with color. And in 17th or 18th centuary, wild speculations
> broke out in Holland leading to tulipomania and govt. had to intervene to
> restore order.
>> What are these viruses?
> How they cause color breaks?
Tulip break virus is a Potyvirus. Potyviruses are the most common plant
viruses (1/4 of all plant viruses). They are ss(+)RNA viruses that express
their genomes by polyprotein processing. Potyvirus particles are long
flexuous rods, aprox. 750x18 nm. They replicate in the cytoplasm of plant
cells, and usually reach high titers. As an indirect result of infection,
cells are not able to produce clorophyll (mesophyll cells in the leaves) or
anthocianins (cells in the petals). Since not all cells are infected,
you see a variegation, which we call "mosaic" in the leaves or "color break"
in the petals. In some cases this variegation is so attractive that
virus-infected plants are actually sold as ornamentals (for example,
geminivirus-infected Abutilons, and tulips).
Dep. of Plant Pathology
University of California, Davis