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Old 12-04-2006, 11:58 PM posted to rec.arts.bonsai
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Default Another episode of "CSI:Bonsai"

Part II: In our last episode, I was sent some fig trees from Florida
that had galls on them. In this episode, I examine them with the help
of an expert.

The samples were Fed-Ex'ed and arrived last Friday in beautiful shape.
This is especially important with bacteria; if the samples get old,
other bacteria begin to invade the tissue, and you can't tell which was
there to begin with.

I agreed to take the samples because my friend Fari is a bacteriologist
and I knew he'd help me. Fari was a professor in Iran and when the
Shah fell, he fled to the US to keep his son safe (otherwise he'd have
been drafted into the Iranian army). Fari had a hard time finding a
proper job, and for a while he worked on a turkey farm, and then for a
corporate plant-care company (the people who put the weeping figs in
the lobby, and the poinsettias by the elevator at Christmas).
Eventually he got a job at the USDA, where he brings great joy to
everyone who works here!

Anyway, he and I unpacked the box, and we were both sure the galls were
caused by the crown gall bacterium (look at the picture on the gallery-
those swollen warty nodules are characteristic). Fari said when he
worked for the plant-care company he saw hundreds of figs with crown
gall, and they looked just like this. Still, we had to be sure. The
first step was to try to isolate the bacterium. Although the galls
have quite a lot of volume, the bacterium is found just under the
surface, not inside it, so Fari used a sterile razor blade to pare off
the rind (which was not sterile), then sliced off a piece just under
the surface of the gall. He put the tissue in a sterile petri dish in
a few drops of sterile water and teased the tissue apart to release the
bacteria. After waiting for half an hour, he took some of the water
and streaked it on a plate of nutrient media.

On Monday I checked the plates and they were dotted with little white
convex colonies of bacteria. They looked like Agrobacterium, but were

Stay tuned for our next episode!

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Old 14-04-2006, 01:10 AM posted to rec.arts.bonsai
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Default Another episode of "CSI:Bonsai"

Part IV: Last episode, we learned more about crown gall; this episode
we learn a simple way to identify it.

Fari the bacteriologist had to go on vacation, but before he left, he
told me a simple way to identify crown gall using only a carrot. This
is something that any of you could do, or your children could do as
science projects.

First I cut some gall tissue as described before and teased it apart in
distilled water to release the bacteria. Then I surface-sterilized the
carrot in bleach, then used a sterile razor blade to cut it into disks.
I put the carrot pieces in Petri plates with moist filter paper on the
bottom and wet the top of each carrot slice with the
bacteria-containing water. I also took some of the colonies I isolated
last week and smeared them on top of some of the slices. I sealed the
Petri dishes to keep them moist and put them under fluorescent light.
Now we wait 2 or 3 weeks. If the bacterium is Agrobacterium, weird
tumors will arise from the carrot slices.

I inoculated the carrots on Monday; I'll be checking them every few
days to look for tumors. Wait patiently for the next episode.

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Old 24-04-2006, 09:32 PM posted to rec.arts.bonsai
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Default Another episode of "CSI:Bonsai"

Today when I looked at the carrot disks, I saw that the xylem
parenchyma had hypertrophied. That's how I talk at work: sorry. The
center of the carrot disk was becoming lumpy, and the lumpiness was
turning green, which is characteristic of crown gall on carrot. I've
posted a picture on the "General discussion" gallery on the IBC
webpage. This means that, without a doubt, the fig with galls was
suffering from crown gall.


PS- My friend Fari wants us to inoculate a baby tomato plant: that's
another surefire method of identifying crown gall. Tomatoes are very
suceptible, and will form galls quickly where you prick them with a
needle coated in bacteria.

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