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DNA diagnostics: key to record yields?

Opportunity to increase plant performance, researchers believe RESEARCHERS at Texas A&M University not only believe every year should yield record crops, they believe science can get significantly closer to that goal.

The average crop yields in the United States are 25 percent of record levels, which are a plant's genetic potential, according to Dr. John Mullet, director of the Norman Borlaug Center for Southern Crop Improvement at Texas A&M.

"There are all kinds of constraints in Texas - environmental stress, temperature extremes, droughts, insects and disease - that keep a crop from reaching maximum production," Mullet said. "So there is a significant opportunity to increase plant yields if we can identify the constraints and make Texas crops better adapted to the environment."

Learning to identify the constraints, Mullet said, means developing DNA chip diagnostics that can detect problems long before they are visible to farmers scouting the fields. It means thoroughly understanding plant adaptation at the DNA level.

"The reason plants are not more productive is that the environment is so complex and the number of genes required to make a plant adapted to the environment is very large," Mullet explained. "Until now, we haven't had the tools to make significant improvement in the environmental stress tolerance of crops."

Mullet and a team of scientists have been awarded $740,000 in a three-year project aimed at mapping genes on the sorghum genome under the National Science Foundation's plant genome program. That, in turn, will enable the group to devise DNA chip-based diagnostic tools for sorghum.

The effort began three years ago with the team building a complex genetic and physical map of the sorghum genome.

As that project nears completion, the team will locate in sorghum individual genes that code for a specific function or trait. Dr. Patricia Klein, a co-investigator on the project, said the project promises many practical applications for producers.

"With remote sensing and DNA diagnostics, we could pick up problems in the field earlier than a farmer could see them because the genes would be indicating the trouble," she said. Likewise, plant breeders could do a fly-by, via satellite, of fields during certain weather phenomena such as drought and be able to determine which types of sorghums are responding well under the circumstances.

"Those could be used to breed new varieties that would be tolerant of the conditions."

Beginning next planting season, Texas Agricultural Experiment Station sorghum breeder Bill Rooney will plant several plots of different sorghum varieties across the state. That will help the research team test the reactions of various genes to the conditions in the field and determine how a gene helps sorghum tolerate drought, for example.

Klein also said growth chambers at the Borlaug Center can simulate many adverse environments.

"That will help us create a known library of changes in gene expression that signal when crops are limited by environmental conditions," she said.

The researchers said the findings for grain sorghum will no doubt lead to greater understanding of other plants. "By comparing the genomics of the sorghum with the DNA of other plants, we can take out what we already know and see what's left," Mullet explained.

In other words, if a gene found in sorghum is spotted when examining the DNA of another plant, scientists already will know how that gene works. The more genes that are understood in this way in sorghum and other plants, the more likely it is that those genes also will be found in other crops and plants.

"I see a day when farmers will routinely sample their fields and either at a local hardware store or at their homes be able to diagnose genetically what is happening to their crops," Mullet said. "And the same technology will be available to help people with lawns, golf courses and other urban landscapes."

Mullet expects the work to take 10 years before the DNA diagnostics are fully developed and gene discovery is complete, but numerous applications will be possible along the way, he said.

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