Researchers at North Carolina State Univ. have found a specific gene in corn
that appears to be associated with resistance to three important plant leaf
diseases.
In a paper published in Proceedings of the National Academy of Sciences,
NC State plant pathologists and crop scientists pinpoint the gene—glutathione
S-transferase—that seems to confer resistance to Southern leaf blight, gray
leaf spot and Northern leaf blight, a trio of diseases that cripple corn plants
worldwide.
Finding out more about the mechanisms behind complex traits like disease
resistance can potentially help plant breeders build the best traits into
tomorrow’s corn plants, says paper co-author Dr. Peter Balint-Kurti, a research
plant pathologist and geneticist for the U.S. Department of
Agriculture-Agriculture Research Service (USDA-ARS) who works in NC State’s
plant pathology and crop science departments.
The NC State researchers joined lead author Dr. Randy Wisser, an assistant
professor at the Univ. of Delaware, and other researchers from the Univ. of Delaware,
Cornell Univ., and Kansas State Univ. in
examining 300 diverse maize varieties from across the globe which are, on
average, as different from one another as humans are from chimpanzees. Using
these diverse varieties of corn allowed the researchers to zero in on the
regions of the genome responsible for conferring resistance to the three
diseases—and thus to varieties that are very resistant to disease.
“We tested the lines for resistance to these three diseases and found that
if a line is resistant to one disease, chances are it’s also resistant to the
other two,” Balint-Kurti says.
The researchers then delved into the question of why this multiple
resistance occurs.
“One hypothesis was that if a corn variety has resistance genes for one
disease, it is likely to also have resistance genes for the others,”
Balint-Kurti says. “The other hypothesis was that the same genes conferred
resistance to multiple pathogens. Our evidence suggests that the latter
hypothesis is more likely. In particular, we have developed good evidence that
a specific gene, a member of a gene family called glutathione-S-tranferases, is
associated with resistance to all three diseases.”
Southern corn leaf blight is a moderate problem in the southeastern United States, Balint-Kurti says, and can be a
significant problem in Southeast Asia, southern Europe, and parts of Africa. Prevalent in hot, humid climates across the
globe, it causes small brown spots on leaves. The spots get larger and
eventually spread to the whole plant. Severe infections can cause major corn
yield losses. Northern leaf blight can be found in the Midwestern corn belt; it
causes cigar-shaped lesions on leaves. Gray leaf spot—which produces an eponymous
effect—is found both in the Midwest and
Southeast. All three pathogens are so-called necrotrophic fungi, or fungi that
kill what they eat.
Balint-Kurti says the study provides “one of the most comprehensive analyses
of multiple disease resistance in plants.”
The research was funded by USDA-ARS, the National Science Foundation, CGIAR
Generation Challenge Program, the N.C. Corn Growers Association, and
USDA-National Institute of Food and Agriculture.