Lubbock, Texas
May 1, 2007
If you have Mom's smile, Dad's
eyes and Grandpa's laugh, you might wonder what other traits you
picked up from the genealogic fabric of the ol' family tree.
Scientists at the Texas A&M
University System Agricultural Research and Extension at
Lubbock are studying the family tree of cotton for much the same
reason.
"Cotton genetic diversity has narrowed in recent years," said
Dr. John Gannaway, Texas Agricultural Experiment Station cotton
breeder. "Many of today's successful commercial varieties share
common parents and grandparents.
"Many scientists believe today's varieties are flexible enough
genetically to handle minor changes but lack enough diversity
for really spectacular change. Aside from limiting fiber quality
and yield potential, narrow genetics makes them more susceptible
to insects and disease."
Gannaway and other scientists believe future progress in cotton
breeding can only be achieved if sufficient genetic variability
remains in global breeding stocks.
The mission of the center's Crops Genetic Research Facility is
to investigate the potential of useful traits lying undiscovered
in the gene pool or germplasm of obsolete and wild cottons
contained in U.S., Russian and French cotton collections. These
traits could help diversify the gene pool from which breeders
draw new varieties in the future.
The U.S. Department of Agriculture's Agricultural Research
Service facilities in College Station house one of three
international collections of cottons. Another resides in France
and another in Uzbekistan, in the former Soviet Union. Breeders
worldwide are evaluating specimens from these collections and
exchanging germplasm in their efforts to improve the cotton
genome.
"These collections contain a wealth of genetic material,"
Gannaway said, "especially when you compare them to today's
varieties. We are screening obsolete and wild cottons for useful
traits such as insect and disease resistance, and drought, salt
and cold tolerance.
Scientists at Lubbock obtain seed from global cotton collections
in small lots, sometimes as few as 10 seeds per lot. Before
their work advances, they must turn a few seeds into more by
growing plants in an environmentally-controlled greenhouse.
Greenhouse manager and Experiment Station research assistant
Leslie Wells supervises seed stocks from planting through
harvest. His skill in making difficult cross pollinations is
critical in developing new cotton lines, Gannaway said.
"Many of the cottons we grow for more seed are photoperiodic,"
Gannaway said. "They will only produce fruit and seed during the
short days of temperate winter."
As these cottons grow and mature, scientists keep a log of their
physical, or phenotypic, characteristics. Remember Mom's smile,
Dad's eyes and Grandpa's laugh?
The lint, or fiber, these cottons produce is also measured,
analyzed and recorded. The lint is hand-, saw- and
roller-ginned, and then characterized using high volume
instrumentation and the advanced fiber information analysis
system.
The Lubbock scientists enter this information into a genetic
database which they share with other scientists and the public.
This database will complement the Texas A&M University System's
cotton breeding program, Gannaway said. An overview of that
program is online at
http://lubbock.tamu.edu/news/2007/LScapesWinter06.pdf .
Under Gannaway's guidance as lead researcher, Experiment Station
research associate Jimmy Mabry and others conduct the greenhouse
screening to make the database a reality.
Mabry grows cotton plants in PVC tubes, measuring the
characteristics of their roots, shoots and leaves and comparing
them to a group of control cottons. The data from these
comparisons could help scientists discover which physical traits
help impart drought resistance and make more accurate trait
selections in the future.
Natalia Castillo, Experiment Station research assistant, screens
cotton grown hydroponically – without soil – for salt tolerance.
Seedlings are incrementally subjected to different
concentrations of salt, which can reach 30,000 parts per
million.
If cotton breeders can impart more salt tolerance to commercial
varieties, farmers on the Texas High Plains could one day
irrigate their crop from the Santa Rosa Aquifer – which lies
underneath the heavily-tapped Ogallala Aquifer, Gannaway said.
"The Santa Rosa Aquifer is estimated to be 100 times larger than
the Ogallala Aquifer, but it has a much higher concentration of
dissolved salts," Gannaway said. "Salt tolerance could open up
the Santa Rosa as an irrigation source."
Other Lubbock scientists are examining natural insect and
disease resistance in obsolete and wild cottons. This resistance
could lead to more "environmentally friendly" varieties that do
not require harsh insecticides and fungicides to thrive in
adverse conditions. Fiber from "greener" varieties may be more
desirable with environmentally-savvy consumers, and help farmers
reduce production costs without sacrificing yield or lint
quality, Gannaway said.
Mark Arnold, Experiment Station research associate, and Monica
Sheehan, Experiment Station research assistant, screen cottons
grown at Lubbock for thrips and Lygus bug resistance.
"Thrips are a serious cotton pest," Arnold said. "Thrips are
very small. They can cause severe crop damage resulting in yield
loss by feeding on the emerging leaves of cotton seedlings.
Those leaves nurture the plant while it is establishing roots
and gaining strength."
Treated seed and insecticides applied in the furrow at planting
help farmers combat thrips, but these methods are expensive and
often only provide a three-week window of protection against
this hungry pest, Arnold said.
Arnold raises thrips on wheat, a favorite host plant, and forces
them to move to neighboring cotton plants by killing the wheat
with herbicide.
"This produces massive thrips pressure on the cotton plants, and
results in a lot of damage to those first four true seedling
leaves," he said. "We measure the leaf damage, identify cottons
that show thrips resistance and subject those to further tests."
Sheehan raises Lygus bugs, a secondary pest of cotton, and
confines their feeding to certain parts of cotton plants using
bug cages. The amount of damage they inflict on cotton fruit and
their ability to lay eggs for another generation are good
indicators of Lygus resistance, said Sheehan, who hopes to
intensify her experiment in 2007.
Raina King, a Texas Tech University graduate student, is working
to develop 'cleaner' cottons that shed the small leaves (bracts)
at the base of each boll a few days after flower blooms open.
Determining whether this trait is dominant, co-dominant or
recessive and finding its DNA location could help breeders
develop upland cottons that require less lint cleaning –
producing cleaner fiber with less ginning costs, Gannaway said.
Scientists at the Crops Genetic Research Facility at Lubbock
have been conducting their cotton research since 2004. The
facility was completed and came on-line in 2003.
"We have developed several reliable methods for screening
obsolete and wild cottons for several positive, heritable
traits," Gannaway said. "The data from these experiments should
give molecular breeders more tools to work with as they look for
ways to diversify, improve and expand our cotton gene pool. That
will benefit global breeding stocks and lead to varieties that
are more flexible and productive."
Writer: Tim W. McAlavy |
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