Ames, Iowa
April 28, 2008
Source:
Integrated
Crop Management NEWS
By John H. Hill and Alan L. Eggenberger, Department of Plant
Pathology. Iowa State
University
As spring planting season begins, it is difficult to predict
those diseases that may be most problematic during the growing
season of 2008. So much depends upon rainfall, temperature and a
myriad of other factors that can affect crops and pathogens.
This includes potential for resistance to various pathogens.
Despite all the management practices we talk about, disease
resistance remains one of the most practical and economic ways
to control plant disease. But, sometimes the genes that confer
that resistance are not so easy to find. Iowa State University
scientists, in research that would not have been possible
without support by soybean check-off dollars, have recently been
working to develop a means to find and characterize resistance
genes to pathogens when resistance has been difficult to find.
Plants can have elaborate mechanisms to recognize and
counterattack against invading pathogens. Resistance occurs when
a plant resistance gene (R gene) recognizes a gene in the
pathogen (avirulence determinant) and starts a complex
biochemical pathway to stop the pathogen. This recognition can
occur either directly or indirectly. In soybean, very little
information exists on genes that are essential for these
biochemical pathways that control defense against disease.
Identification of the genes that are essential for resistance is
key to development of disease resistant soybean varieties.
To establish a road map that will be effective for examination
of resistance to a multiplicity of soybean pathogens, the
interaction of the resistance gene Rsv1 with soybean mosaic
virus has recently been examined. Through utilization of several
different methods, two genes of the virus have been identified
as the avirulence determinants. By means of a unique
evolutionary approach, researchers identified specific mutations
in the viral genes that result in overcoming resistance. This
occurs as a result of selection pressure imposed by R genes in
soybeans.
Resistance to soybean mosaic virus was chosen for study because
the genetic studies of this system are much further along than
for other soybean pathogens. Knowledge from these studies is
being used as a guide to unravel the disease resistance network
in soybean. Resulting from research supported by check-off
dollars, it is revealing clues that will allow identification of
genetic resistance to numerous yield-robbing soybean pathogens.
Stay tuned. Improved resistance against several different
problematic pathogens is on the way!
John H. Hill is a professor in the Department of Plant Pathology
working on virus diseases of Iowa crops. Alan L. Eggenberger is
an assistant scientist with research responsibilities on virus
diseases of soybean. |
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