Virused Bulbs
Nathan Lange (Mon, 07 Apr 2014 19:05:27 PDT)

The implication of the dark pink-flowering Sparaxis photo posted
below a title of "Virus" is that a virus is known to have caused the
pattern seen on the petals in the photos and that this pattern
represents a known symptom of viral infection. I do not believe this
is the case. Finding a virus does not establish cause and effect, and
is clearly not a definitive diagnosis for the cause of the observed
color pattern. Many, if not most, plants are infected with viruses
with no visible symptoms, as Mary Sue admits to finding out for
herself. To correctly diagnose what is going on with this Sparaxis
flower, the next logical step would have been to attempt to infect
other Sparaxis and/or closely related genera to see if one can
replicate the same pattern of speckled petals in a previously
uninfected plant. Transposable elements are not transmissible. Also,
one could attempt to grow out seeds from this plant. If the resulting
seed grown plants also exhibited this trait, then that would strongly
rule out virus. However, if no seed-grown plants exhibit this trait,
neither possible cause is ruled out since we know nothing about the
genetics of this hypothetical tranposon.
In this instance, I think the cause is far more likely to be a
transposon than virus for four reasons:
1. The margins of the white sectors seem fairly well defined, not
diffuse as is typical of viral infection, although this is difficult
to say conclusively given the photo's limited focus.
2. The sectors seem to follow the developmental pattern within each
petal as if the pigment machinery were turned off and back on very
early during development along dividing cell lines.
3. The white sectors are white and not light pink, as if a transposon
is completely turning off all anthocyanin production. A virus doesn't
usually completely turn off all pigment production and would probably
create lighter pink areas of varying intensity.
4. There are known, identified examples of transposons affecting
petal color patterns which resemble the pattern seen with this Sparaxis flower.

I think this is an interesting photo but posting it under a title of
"Virus" adds to the confusion encountered by home gardeners seeking
answers and may lead someone to needlessly destroy a wonderful new
cultivar. I recommend its removal from the "Virus" page.

Nathan

At 04:38 PM 4/7/2014, you wrote: