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Whitefly research helps cotton producersTexas 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 to 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." --------CUTLINES------ 1.) Maggie Toothaker, a graduate student at Texas A&M University, shows a cotton leaf with a spot marked for whitefly counts. Her whitefly research earned a top award at the Beltwide cotton Conference in New Orleans. (Texas Agricultural Experiment Station photo by Edith Chenault.) 2.) Maggie Toothaker retrieves a boll of cotton from one of the plants she used in her whitefly research at Texas A&M University. Toothaker is trying to select plants that have the best whitefly resistance characteristics. (Texas Agricultural Experiment Station photo by Edith Chenault.) A 6 2/26/07 None Date: 2/16/07
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