Wooster, Ohio
May 7, 2009
A new species of Pythium, a water
mold that attacks soybeans and corn in saturated soils, has been
identified in Ohio.
Anne Dorrance, an Ohio State
University plant pathologist with the Ohio Agricultural
Research and Development Center, said Pythium delawarii was
labeled as a new species when its characteristics didn't match
any of the more than 200 described Pythium species. There are at
least 24 species found in Ohio that impact corn and soybeans.
The research was published in the March/April issue of the
journal Mycologia.
"To identify a new species is an interesting process because
Pythium species have different shapes. Their mycelium takes on a
different shape and their fruiting structures can be different
from one species to another. This new species didn't fit any of
the known Pythium descriptions," said Dorrance, who also holds a
partial Ohio State University Extension appointment. "The final
evidence was the DNA sequencing, which didn't match any of the
described species. It was proof that we indeed did have
something that wasn't in any of the data banks."
Pythium pathogens are water molds that attack soybean or corn
seeds, as well as a number of other crops via the plant roots in
saturated soil conditions. They are one of the major causes of
crop replants, and are becoming more economically important
because of the continued rise in seed costs.
"What used to not be as big of an issue far as crop management
decisions is becoming a bigger issue. Seed is a huge input for
producers and a huge input for companies to produce it. With
seed costs continuing to increase, producers can't afford to be
replanting their crop due to disease issues," said Dorrance. "We
are seeing more instances of Pythium over the past five years
and it's more important in Ohio because we are farming clay
soils that just hold the water. Getting plants up and going in
these heavy clay fields is really a challenge."
The new Pythium species was isolated from an Ohio field that
experienced persistent stand establishment problems. So far the
new species has been identified in a small number of locations
across the state and doesn't appear to be very aggressive.
"This isn't a super aggressive species. The extent of its
infection was forming lesions on the roots," said Dorrance. "But
it is an unusual species in that it thrives in warmer
temperatures later in the season on older plants. People tend to
identify Pythium mostly as a disease that thrives in cold soils
in the spring on younger plants. There is such a broad range of
species out there that it's unwise to use one label for all
species. Never make a rule because there will be something in
biology that will break it."
Dorrance said that the discovery would aid in future management
of Pythium diseases and help in the breeding of new cultivars
for resistance and new chemistries for seed treatment compounds.
"Right now we are looking at how fungicides affect it and
studying the current germplasm for resistance," said Dorrance.
The research is being funding by the Ohio Soybean Council,
Pioneer, Syngenta, BASF, Valent and an OARDC SEED grant.
Writer: Candace Pollock
Source: Anne Dorrance, OARDC, OSU Extension |
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