Washington, DC
November 2, 2007
By Stacy Kish
Important cereal crops, such as wheat and barley, are
susceptible to a fungus, called Fusarium graminearum that
is responsible for head blight disease. Researchers recently
sequenced and annotated the genome of this fungus, shedding
light on how it is able to survive in rapidly changing
environments. The new knowledge could lead to new ways to combat
the harmful pathogen, which has caused more than $10 billion in
crop losses over the past 10 years.
USDA scientist H. Corby Kistler, along with Christina Cuomo of
the Broad Institute of MIT and Harvard and colleagues at a
consortium of universities and labs around the world, used a
whole genome shotgun approach, a faster approach that involves
shredding and replicating the genome in order to sequence the
Fusarium graminearum genome, bypassing the need for a physical
map. The scientists found very few repetitive sequences in the
genome. Instead, they discovered that most mutations occur at
particular points in the genome sequence, specifically
associated with plant-fungus interactions. The specific
locations of the high sequence diversity in the genome may
explain the ability of the fungus to adapt rapidly to changing
environments and hosts.
Plant-fungus interaction is like an intricate game of cat and
mouse. If the plant can detect the fungus, it can mount a
defense and ward off the fungus. However, the newly identified
genome sequence is like a closet full of disguises, cloaking the
fungus from plant detection. If the fungus can disguise itself
and gain access to the plant, it can override the plant's
defenses and cause disease.
The growth of this fungus is largely dependent on weather
conditions. The fungus thrives in cool wet conditions and
infects unsuspecting fields by releasing an assault of
pinprick-sized spores. The tiny spores colonize the edible
portion of newly emerging plants and grow down through the
stalk. Once a fungal mass is established, the fruiting
structures of the fungus penetrate the plant's leaves, in effect
suffocating the plant. During the winter, the fungus goes
dormant in the debris of the withered, bleached heads of the
blighted grain. As spring approaches, the cycle begins again.
To date, cultural disease management strategies, such as crop
rotation, tillage practices and field sanitation, resulted in
partial control. Preventative application of fungicide has also
shown moderate disease control.
The recently identified portion of the Fusarium genome is like
the game day playbook for fungal attacks on plants. Future work
focused on the high sequence diversity may result in
environmentally-friendly ways to combat this important
agricultural pathogen.
The results of this research study are presented in the
September 7, 2007, issue of the journal
Science.
The USDA's Cooperative
State Research, Education, and Extension Service (CSREES)
funded this research project through the NRI Microbial Genomics
program. CSREES advances knowledge for agriculture, the
environment, human health and well-being, and communities by
supporting research, education and extension programs in the
Land-Grant University System and other partner organizations.
For more information, visit www.csrees.usda.gov.
This research result is a service of the USDA Cooperative State
Research, Education, and Extension Service. |
|
