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![Title: Attack... of The Killer Fungus!](/peth04/20041117054716im_/http://ars.usda.gov/is/kids/farm/story4/titlehead.gif) |
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Let's say you're taking a walk on a farm.
You notice something
green growing in a bed where a crop has been
planted. You turn to the person who runs the farm, and you point out your
discovery. You'd expect the farmer to be happy, wouldn't you? Green is good, isn't it? |
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To most farmers, yes. But if you showed your
find to certain members of the farming community, you probably wouldn't get
them to smile. Instead, they might say "Ack!" or just shake their heads no. |
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Have you entered the "Twilight Zone," where nothing is exactly what it
seems?
Nope, you've just entered the strange and
fascinating world of the mushroom farmer, where green is bad and sunshine doesn't matter. It's a
world that Gary Samuels and Sarah Dodd entered a few years ago. They're
mycologists (my-CALL-ah-gists) with the
Agricultural Research Service, and they
study fungi such as mold and mushrooms (So what's the
difference between the two? Click here. ) |
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Back in the early-to-mid 1990s, farmers in
Pennsylvania--the "mushroom capital" of the United States--were under siege. A
green mold was attacking their crop. In one
county, some mushroom farmers lost between 30 and 100 percent of
their harvest to this emerald invader. |
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A Good Fungus Gone Bad? Scientists studied the problem,
and a few wrote scientific papers about it. They identified the
killer green mold as Trichoderma harzianum (trick-ah-DERM-ah
hart-ZEE-ah-num).
But when Samuels and Dodd looked at the evidence, they weren't sure that this
mold was to blame. They decided to investigate further. |
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Before being accused of causing green mold on mushrooms, Trichoderma harzianum was
considered a "good" fungus. It was used to control
"bad" fungi that cause plant diseases, and it
showed an ability to enhance plant growth--like a fungal fertilizer. Some
experiments showed that it could also help break down pesticides in soil and
prevent certain toxins from forming. |
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The Investigation
and Discovery: When Samuels and Dodd looked
closely at samples of the killer green mold, they saw something strange. The mold
could actually be separated into four distinct types. There were differences in
their DNA and in how they looked under a microscope, how fast they grew, and
how they smelled. Only two of these types were actually causing mushrooms to get sick. The other two were
harmless. |
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Trichoderma
harzianum, the good fungus, was
one of the harmless types of mold that
Dodd and Samuels identified. The other was Trichoderma atroviride
(trick-ah-DERM-ah
at-tro-VEER-eh-day).
It turns out that the two types of mold causing the mushroom disease were forms of a new species that
didn't have a name.
Because
Samuels and Dodd discovered the new species, they got to name it. Samuels chose
the name Trichoderma aggressivum (trick-ah-DERM-ah
ah-gress-SEE-vum)
because the mold is so aggressive against mushrooms.
By Amy
Spillman, formerly Agricultural Research Service, Information
Staff |
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