Manhattan, Kansas
December 10, 2008
Sometimes less is more. That´s how
Kansas State University wheat
breeder, Allan Fritz, is now approaching the problem of getting
durable leaf rust resistance into new varieties.
Combining several resistance genes that, individually, impart
only a minor level of leaf rust protection to all races of leaf
rust should offer more durable resistance than using a single
gene with very strong resistance to specific races of rust,
Fritz said.
"Leaf rust long has been one of the biggest concerns for wheat
breeders in Kansas and the Great Plains," he said. "In most
cases, just as soon as wheat breeders release a new variety with
strong leaf rust resistance, a race of leaf rust that can
overcome that resistance comes along to attack the variety."
To try to get ahead of this problem, Fritz is changing his
approach. Instead of focusing on strong, race-specific sources
of leaf rust resistance, he is now working with plant
pathologists from the U.S. Department of Agriculture´s
Agricultural Research Service and CIMMYT (International Maize
and Wheat Improvement Center) in Mexico to incorporate so-called
"minor" genes for leaf rust resistance.
"None of these minor genes in itself provides strong resistance
to leaf rust. A variety minor gene resistance won´t be perfectly
green during a leaf rust outbreak. But there will be fewer leaf
rust pustules, they´ll be smaller, and they will take longer to
develop on the leaves," he explained.
"When three or more minor genes for leaf rust resistance are
combined, a variety will have very acceptable resistance to all
races of leaf rust. In Mexico, varieties with minor gene
resistance have maintained that resistance for many years.
That´s what we´d like to see in our new wheat varieties."
Fritz and his team at K-State have been crossing a genotype
called "Amadina" onto Overley, a hard red winter wheat variety.
Amadina has four minor genes for leaf rust resistance.
"We currently have 11 such lines in the Kansas Intrastate
Nursery tests. If all goes well with these experimental lines,
we may have a new variety with durable leaf rust resistance
ready for release in 2011," he said.
Some of the minor genes for leaf rust resistance also carry
minor gene resistance for stripe rust, Fritz added. As a result,
the new varieties developed for minor gene, durable,
slow-rusting leaf rust resistance will also have the same type
of durable resistance for stripe rust.
"If this type of durable leaf rust and stripe rust resistance
can be incorporated into most or all of our new wheat varieties,
that will give us more resources to focus on other traits in our
breeding problem, such as scab resistance, Hessian fly
resistance, quality, and others," the wheat researcher said.
K-State Research and Extension is a short name for the Kansas
State University Agricultural Experiment Station and Cooperative
Extension Service, a program designed to generate and distribute
useful knowledge for the well-being of Kansans. Supported by
county, state, federal and private funds, the program has county
Extension offices, experiment fields, area Extension offices and
regional research centers statewide. Its headquarters is on the
K-State campus, Manhattan. |
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