Geneticist Gina Brown-Guedira
and molecular biologist John
Fellers review DNA marker data
from disease-resistant wheat
breeding populations. (K9754-2)
Everyone likes to take shortcuts in
time-consuming tasks. And wheat breeders are no exception. Someday, wheat
breeders may be able to use new molecular tools being developed by
ARS in collaboration with Kansas State
University and the Kansas Wheat Commission.
These tools show promise for reducing the time it takes breeders to move
important quality and resistance traits into breeding populations of wheat
using conventional breeding techniques. Currently, it can take as long as 10 or
more years to develop new wheat varieties.
“Using molecular (or DNA) markers may shorten the task of improving insect
and disease resistance while maintaining good yield and quality
characteristics,” says plant geneticist Gina L. Brown-Guedira in ARS'
Plant Science and Entomology Research Unit in Manhattan, Kansas.
Molecular markers are small pieces of genetic material—DNA—that can
be seen on a gel and are known to be reliably linked in this case to resistance
genes. They offer breeders a fast and safe way to identify wheat resistant to
pathogens.
Brown-Guedira and ARS molecular biologist John P. Fellers are focusing on
finding markers that will ultimately be used to incorporate longer-lasting
resistance to major wheat diseases, such as leaf rust, Karnal bunt fungus, and
fusarium head scab. (See “Tagging New
Leaf Rust Resistance Genes in Wheat,” Agricultural Research,
May 2001, p. 19.)
One major accomplishment by scientists in this laboratory is identification of
a molecular marker for a gene that holds the key to nearly 25 percent of the
resistance to Karnal bunt fungus. This fungus is currently quarantined by 72
countries, making it a threat to our export markets. Besides yield losses,
Karnal bunt disease lowers the quality of flour used for food.
Scientific studies on Karnal bunt are limited to geographic areas where the
fungus is present. Working with the fungus in noninfected areas is restricted
to guard against potential spread.
“But markers can be used at any stage of plant growth without having to
infect plants with disease,” says Fellers.
So far, researchers in the United States and abroad have identified markers for
disease-resistance genes, insect-resistance genes, and quality and
environmental stress genes in wheat that can be applied to wheat breeding
programs.—By Linda McGraw, formerly with ARS.
This research is part of Plant, Microbial, and Insect Genetic Resources,
Genomics, and Genetic Improvement (#301) and Plant Diseases (#303), two ARS
National Programs described on the World Wide Web at
http://www.nps.ars.usda.gov.
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