Scientists try to build a

Better Banana

Genetic mapping could lead to less use of pesticides 

Keay Davidson / SF Chronicle 18jul01

After long service as a staple of breakfast cereal, a prop of slapstick comedies and a demonstration aid in sex-education classes, the humble banana is entering the world of big-stakes genetics research.

An international team of scientists plans to announce their plans Thursday to map the genetic structure of the banana, hopefully within five years.

The goal: to figure out how to invent, in effect, a superbanana -- specifically, one that can be grown with less environment-damaging pesticides.

Mapping of the banana genome would be performed by different centers around the world, including five in the United States. The closest to California would be the Arizona Biomedical Institute at Arizona State University in Tempe.

The scientists plan to map the genome of a wild species of banana that grows in Southeast Asia. Scientists have already mapped much or all of the genetic sequence for humans, mice, certain bacteria, yeast and the fruit fly.

If the project is successful, then bananas would enter the history books as "the first exclusively tropical fruit to be (genetically) sequenced," said project leader Emile Frison, director of the International Network for the Improvement of Banana and Plantain, or Inibap, based in Montpellier, France.

Bananas are an important food in impoverished and developing nations, along with rice, wheat and corn. In modern times, over-cultivation of a few popular brands has diminished their genetic diversity, rendering them more vulnerable to pests and plant diseases such as the scary-sounding fungus known as "Black Sigatoka."

Some banana growers protect their crops with pesticides, which can damage the ecosystem.

Hence "a coordinated effort by scientists worldwide is needed to unlock the (genetic) diversity found in bananas that still grow and reproduce in the wild, " Frison said in a statement issued Tuesday.

"More than a popular snack, bananas are a staple food that many African families eat for every meal," Frison said. "This is our chance to develop a crop that won't fail for them and that may help lift them out of poverty."

"If we manage to mobilize the resources that we expect, this (project) is going to be an absolutely major breakthrough for small-farm farmers," said Frison, a plant virologist by training, in a phone interview yesterday.

Mapping the banana gene could benefit plant science in general, too, the scientists claim.

"If we've learned anything from genetics, it is how little we know about biology," said one member of the consortium, Claire Fraser of the Institute for Genomic Research in Rockville, Md. "We expect that the banana genome sequencing will reveal surprising insights into the evolution of plants."

One banana-threatening virus is known as banana streak virus. The virus works by embedding itself in the banana's DNA, the double-helical coil of molecules that transmits the genetic code in plants and animals. For some reason, banana streak virus emerges from the DNA to ravage bananadom only at certain times.

Why those times and not others? Inquiring banana scientists want to know. Hence, one goal of the project is to understand the dynamics of banana streak virus.

Inibap is run by the International Plant Genetic Resources Institute of Rome. Nations participating in the banana-mapping project include the United States, Australia, Belgium, Brazil, the Czech Republic, France, Germany, India,

Mexico and the United Kingdom.

In the United States, the participating scientists include Charles J. Arntzen of the Arizona institute, plus researchers at the International Laboratory for Tropical Agricultural Biotechnology in St. Louis, the University of Georgia in Athens, Ga., Case Western Reserve University in Cleveland, and TIGR in Rockville.