COLLEGE STATION, TEXAS, USA--It's not cloning, and it's not genetic modification. But researchers at the Texas Agricultural Experiment Station use biotechnology to diagnose desired traits in rice and assure that new varieties have those components at the DNA level. So far the technology has found the DNA markers for starch quality and for resistance to blast, a fungal plant disease that takes its toll on rice yields throughout the U.S. growing regions and much of the world.

"It's faster, cheaper and better to use this technology in breeding new varieties," said Dr. Bill Park, Experiment Station biochemist and project collaborator. "And it is being put to use in the field more quickly than research findings often are."

Two new varieties, Cadet and Jacinto, already have been released and are growing in Europe, noted Park, who worked with Dr. Anna M. McClung, head of the U.S. Department of Agriculture-Agricultural Research Service Rice Research Unit at the Texas A&M University Center at Beaumont.

The technology comes at a good time for the rice industry, which is struggling to remain viable.

In January, private companies announced that rice had been genetically mapped--the first crop plant whose genome mapping was completed. With the DNA sequence of every gene known, researchers now are trying to delve further into the code to "mark" what each gene expresses in the plant. That's where the work of Park's team plays a role.

The first marker they found regulates amylose, a component of starch.

"In rice, high amylose means that the grains are firm and separate, and low starch means you can eat it with chopsticks because it sticks together," Park said.

A problem in breeding new varieties, he explained, is that the air temperature while rice is growing influences the amount of amylose that the plant produces. Standard methods for determining the amount of amylose produced among different rice breeding lines can be misleading because the amount produced is so sensitive to the field conditions where the rice is grown.

Therefore, if a plant breeder crosses two varieties with the intention of getting high amylose, but temperatures are unusually cold or hot during the growing season, the breeder would not know if the rice line's amylose level was due to genetics, or to the weather.

Park compared it to eating a cheeseburger before getting a cholesterol check--a person would not know whether a high cholesterol reading really indicates high cholesterol, or merely reflects that day's diet.

By diagnosing rice in breeding programs with DNA markers, however, scientists can accurately decide whether to keep working with progeny from a cross, or to cease selection. "Breeders don't have to worry about unusual weather giving false reads on a potentially good variety," Park explained.

With the findings on amylose verified, the team tackled another problem for the rice industry--blast disease.

Breeders try to breed resistance into rice varieties, using resistance genes that are available in the rice gene pool, so that farmers apply less pesticide to protect their yields. That decreases production costs and helps protect the environment. Because this fungus is continually evolving, new genes for resistance need to constantly be added to new varieties to maintain the resistance.

Thus, breeding programs put tremendous effort in evaluating breeding lines for resistance to this pathogen.

Connie Bormans, a biochemistry doctoral student on Park's team, said a major problem with stacking multiple genes for blast resistance is that some tend to "mask" others. In other words, researchers want multiple layers of resistance--but with traditional methods, they can't tell if there is one layer or multiple layers of resistance. That is where DNA markers come in.

"Breeders tend to use very similar strains of rice plants as parents for new crosses in trying to create better varieties," Bormans said. "Because the rice plants are closely related, that makes it hard to find the differences in DNA."

Bormans' 6-year effort has found markers for four major blast genes, however, and all have been put to work in the rice breeding program at Beaumont. The lab annually screens about 3,000 rice strains for blast resistance for U.S. breeding programs, according to USDA-ARS.

In June, the team plans to host a workshop to show other public breeding programs how to use these markers to augment conventional breeding programs.

"It is a system that actually works in the real world," Park added.

The team is proud not only of the findings, but also of the collaboration that took the work from College Station to Beaumont, then into the field in a relatively short time. Park said the DNA diagnostics can shave as much as half the time off of the breeding process; they allow development of a new variety in 5 to 7 years vs. 10 years in traditional breeding program.

The team and others plan to use the marker-assisted technology to help find resistance to other serious rice diseases, and to improve milling quality, plant height, and other quality traits for specialty rices.

Contact: Dr. Bill Park, (979) 845-8868, wdpark@tamu.edu

** NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is distributed for research and educational purposes only. *