Published on 01/16/03

Scientists coming to grips with plant microbes

By Brad Haire
University of Georgia

They can help a plant grow stronger, or they can kill it. And we know relatively little about how or why they do what they do. But a University of Georgia scientist says a new initiative can find some answers.

Farmers and gardeners around the world, whether they know it or not, depend heavily on beneficial plant-associated microbes to help their crops grow and fight off diseases.

Other plant-associated microbes, however, cause diseases that destroy plants, says Scott Gold, a plant pathologist with the UGA College of Agricultural and Environmental Sciences.

Microbes are microorganisms that can be found on or in most higher organisms, including animals.

Disease-causing microbes include viruses, bacteria, nematodes and fungi. Worldwide, these diseases annually destroy about $200 billion in potential food and fiber crops. Other microbes help plants process food.

Little is known

Despite the importance of plant-associated microbes, little is known genetically about how they work, said Gold, who is also a geneticist.

That’s why Gold is helping spearhead the American Phytopathological Society’s Plant-Associated Microbe Genome Initiative. The initiative calls for a five-year, $500 million public effort to develop complete genetic maps of important plant-associated microbes.

No funding has been secured, yet, for the initiative, he said. But the APS Public Policy Board has presented this information to stakeholders in meetings in Washington and plan to do so again in March.

Secure the future

The study will not only help scientists know more about plant- associated microbes, it will help insure the future of agriculture and protect the world’s food and fiber supplies and the environment, he said.

The world’s population is increasing. But the world’s food and fiber supplies are produced on fewer and fewer acres. It will become more important each year to make sure those few farm acres are as healthy and efficient as possible.

Certain microbes, too, can become weapons in the wrong hands. Engineered “super-strains” of some disease-causing microbes could cripple a nation’s economy.

“The U.S. agriculture system is diversified,” he said. “No single attack is going to destroy us. But an attack could hurt and cause a lack of confidence in the food supply.”

It doesn’t have to be an intentional microbial attack, he said. World trade is pushing countries into more frequent contact. And microbes, good and bad, are ready to travel, he said. A microbe that's not much of a problem in one country could economically devastate another.

Right now, scientists in California are baffled by the appearance of an exotic microbe, which causes a disease that kills oak trees at an alarming rate. And Florida’s multibillion dollar citrus industry is trying to prevent the spread of a nasty microbe that causes citrus canker, a deadly disease. There is no cure for either problem.

Understanding microbes on a molecular level would streamline identification of such domestic villains and foreign invaders, Gold said. That’s not possible right now.

“We could also tell whether or not the pathogen has been (genetically) manipulated in some way,” he said.

Novel tools

Genetic research can lead the way to novel management strategies for disease-causing microbes at home. U.S. farmers spend roughly $600 million on agricultural fungicides each year to fight diseases.

“This (research) could lead to more specific chemicals that are more focused on a problem and more environmentally friendly,” he said.

The genetic information the initiative could spur would be available forever, he said. And it could provide information that can be used for generations.

“It’s not a single shot,” he said. “It’s the foundation for many years of continued beneficial research.”

Brad Haire is the former news editor with the University of Georgia College of Agricultural and Environmental Sciences.