Lexington, Kentucky
December 3, 2008
Every corn grower’s nightmare is
to wake up to a field of downed corn caused by corn stalk rot.
While there is no cure for stalk rots,
University of Kentucky College
of Agriculture researchers are studying and working toward ways
to fight the fungus that causes anthracnose stalk rot.
There are several types of stalk rot, but anthracnose is one of
the most common. It is caused by a fungus called Colletotrichum
graminicola. It is unique from other types of stalk rot, because
its symptoms are visible through discolorations on the leaves of
the plant as well as the stalk. Once a plant is infected with
anthracnose, its cells begin to rot and die, which can lead to
weakened cornstalks and lodging. A widespread epidemic of the
infectious stalk rot disease has not happened in the state since
2000, but stalk rots account for an approximate 6 percent yield
loss each year according to some industry estimates.
For the past 12 years, researchers in the UK Department of Plant
Pathology, led by Plant Pathologist Lisa Vaillancourt, have been
at the forefront of learning about all aspects of this disease.
They have found several interesting things since beginning the
project.
One approach they have taken is to create random mutations in
the fungus, removing just one component of the fungus with each
mutation. Then the mutants are screened for changes that destroy
the fungus’ ability to cause disease. When studying this,
Vaillancourt and her team discovered that an important enzyme
that controls secretion of proteins to other parts of the cell
and outside of the fungus is crucial for disease. When this
enzyme’s operation is interrupted, the disease does not occur.
“It was really a surprise find for us because this enzyme is
referred to as a ‘housekeeping protein,’ which means it is a
basic function the fungus needs to survive,” she said. “Our
mutation succeeded in destroying its ability to cause the
disease, but not its essential function for life. That means
this enzyme has a special function just in causing disease that
we never knew about before.”
While this is an important discovery, researchers are studying
further to determine what part of the protein regulation causes
the fungus to lose its ability to cause disease. They are also
examining ways to help cornstalks destroy this function in the
fungus to prevent the disease from taking control of the plant.
A very similar disease to anthracnose stalk rot affects sorghum.
While the diseases are similar, the fungus that causes
anthracnose stalk rot in corn cannot infect sorghum, and the
sorghum disease does not infect corn. UK researchers have
discovered the corn fungus apparently is able to suppress the
defenses of the corn plant, but sorghum quickly recognizes that
fungus and responds by killing it.
“We are trying to understand the basis for this non-host
immunity. Our hypothesis is there is a specific protein
‘receptor’ in corn that the fungus targets when it suppresses
corn’s defenses, and that there is a different, related receptor
in sorghum that the sorghum fungus targets,” Vaillancourt said.
“If we could change these proteins, we might be able to make
corn immune to the corn fungus in the same way that sorghum is
immune and vice versa.”
In addition, she and her team are observing the way the fungus
works its way through cornstalks and studying the basic biology
of the disease with the goal of determining which components are
critical for the disease to function. Once the group finds the
critical points in the disease cycle, they will look for ways to
suppress or prevent them from occurring.
“The more we learn about the biology of the disease, the closer
we are to being able combat it,” Vaillancourt said.
While research is ongoing, producers can do several things to
lessen the chances of their crops developing this disease.
Applying the appropriate amount of nitrogen, planting at proper
plant densities, planting more resistant varieties, controlling
corn borer damage and scouting for the disease late in the
growing season helps control losses from stalk rots. Follow the
UK fertilizer recommendations to keep the crops from being
stressed from too little or too much nitrogen. AGR-1, the
publication on UK fertilizer recommendations, is available
online at http://www.ca.uky.edu/agc/pubs/agr/agr1/AGR1.PDF and
through your local Cooperative Extension Service. A UK extension
publication that discusses general guidelines for stalk rot
control is available online at
http://www.ca.uky.edu/agc/pubs/ppa/ppa26/ppa26.htm.
UK College of Agriculture, through its land-grant mission,
reaches across the commonwealth with teaching, research and
extension to enhance the lives of Kentuckians. |
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