College Station, Texas
January 30, 2007
Maggie Toothaker does not want to
be a pencil pusher. Her graduate work at
Texas A&M University is
enabling her to achieve her goal, while also helping cotton
producers in the Rio Grande Valley of Texas and in California.
Toothaker's master's thesis is focusing on evaluating converted
race stocks for resistance to whiteflies, a major pest of
cotton. Race stocks are just a little more specific than the
genus and species, much like race is in humans, she said.
Whiteflies leave a sticky residue, which makes ginning more
difficult.
They also transmit diseases from plant to plant and limit
nutrient availability to the plant.
The research race stocks she uses are just one or two
generations from wild species in cotton, said Toothaker, who was
raised in Schertz on the outskirts of San Antonio and far from
cotton fields.
She is continuing work begun by Brandon Ripple, another master's
student who graduated from Texas A&M in 2004. His work
identified six out of 116 race stocks in cotton that showed
whitefly resistance characteristics.
Toothaker is trying to select the best individual plants—from
each of the six race stocks—that show the characteristics of
resistance in plants.
She is measuring the days to adulthood and mortality in the
insects.
She rears whiteflies on cucumbers and cantaloupe in a university
greenhouse so the insects don't have a preconditioned preference
for one breed of cotton variety.
Seven to eight adult whiteflies are placed in a "clip cage" (a
small, round cage that clips to the leaf) for 24 hours.
Toothaker then removes the adults, counts the number of eggs
that have been laid, and replaces the clip cage (without the
adults).
"Crawlers" hatch from the eggs after about 10 days and settle in
the caged area; they will not move again until they complete
development as adults. This allows Toothaker to remove the cage
after two weeks and count the number of "settled" nymphs every
day until all of the whiteflies have emerged as adults or died.
Plants' resistance can show up in a couple of ways: The eggs
will not hatch or the insects will not live to adulthood. By
counting repeatedly, she can compare plants within a race stock
to determine the variability in mortality. In other words, if
more whiteflies consistently die on the race stocks than on the
control group, which is a couple of varieties planted now, it
exhibits the characteristics of resistance, she said.
She is in the process of harvesting the bolls of cotton to
retrieve the seeds. Those seeds will be turned over the cotton
breeding lab for further research work with Dr. C. Wayne Smith,
professor with the Texas Agricultural Experiment Station.
Her work is supported by a grant from Cotton Incorporated and
recently earned a first place in the master's students' oral
presentations at the Beltwide Cotton Conference in New Orleans.
Toothaker hopes to graduate from Texas A&M in August and work as
a crop consultant.
"Maggie understands production agriculture," said Dr. Marvin
Harris, Experiment Station professor and chair of her graduate
committee.
"Maggie's fine work today is also a firm foundation for a
successful career in production agriculture for decades to
come," Harris said.
"I knew I wanted to be in agriculture at the age of 11, so I've
known I wanted to go to (Texas) A&M since I was 11," said
Toothaker, who graduated with a bachelor's degree in agronomy
and entomology a couple of years ago.
"I like being in the middle of a cotton field in the middle of
nowhere."
Writer: Edith A. Chenault |