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.”