Banana (20 page)

R
ONY SWENNEN,
the banana scientist who heads the Belgian lab, started out as a conventional banana breeder. He'd just graduated from the Catholic University at Leuven—the same place where he'd later open his banana genetics lab—and he was searching for adventure. “I'd always dreamed of being somewhere very remote,” he says. In 1978 the United Nations Food and Agriculture Organization offered him a job in Africa. He'd be attached to one of the continent's most active research organizations, the International Institute of Tropical Agriculture; he'd be traveling through the heart of the continent, collecting banana specimens to send back to Leuven, where they'd be stored for future research. (Belgium has been involved in Africa since the late nineteenth century, when King Leopold II sent explorer Henry Morton Stanley—the rescuer of Dr. David Livingstone—to help set up the colony of the Congo.)

Swennen saw firsthand the devastation Black Sigatoka wrought when it arrived in Africa: Many villages seemed to be on the verge of the doomsday scenario, with their sole source of food in danger of being wiped out. Suddenly, his research developed a very sharp focus. “We had to learn to breed new bananas faster than ever before,” Swennen says. He was sent to Nigeria to build a research station. It was there that Swennen made one of the first breakthroughs that shifted the momentum in banana breeding from Honduras to newer research organizations around the world: He determined a way to get more seeds from bananas (at least, those that produce seeds). It turns out that the fruit produces that basic reproductive material in cycles. “If you really observe the plant,” Swennen says, “you learn when to look for the seeds—the right days of the year, the right hours of the day.” Like most other plants and animals, bananas have a specific fertility rhythm, but it is subtle enough that nobody had detected it. Swennen's techniques—careful, numeric tracking of banana plants and analyzing those numbers to find patterns—resulted in a quantum improvement: Plants that yielded just one or two seeds across a hundred-acre plantation were suddenly producing up to two hundred per bunch.

That led to a revolution in the way bananas were bred. The older method was to mate a wild, seeded fruit with an edible one. That produced plenty of new and interesting hybrids but none that were truly satisfactory, because one half of the happy couple was, by definition, not edible. “It wasn't our intention,” Swennen says, “but our results showed that the old way of breeding wasn't entirely sound. The crosses were getting resistance from their ‘mothers,' but the [seeded] ‘father' gave them very poor fruit.”

Swennen's approach was to use fertile plantain varieties—there are about forty in the world—and cross them with the more common sterile fruit. The results were hardier bananas that tasted good. But that still wasn't enough: Swennen's bananas needed further improvement to resist Black Sigatoka, which was the only way they could function either as a hedge against hunger or as the raw material for a commercial fruit. Over the next dozen years, Swennen became one of the most successful—if not
the
most successful—breeders in banana history.

African banana market.

Enough of his bananas were grown in enough places that Swennen was made an honorary chief, complete with ceremonial walking stick. On a shelf in his office in Leuven there's a photo of the young scientist in the full red garb of an African tribal leader. Somewhere in Nigeria, perhaps eating a bred banana, is a young man named Swennen Akauque: when the child was born, a grateful family endowed him with the Belgian researcher's first name.

SUCCESS AT LAST?
Honors and tributes aside, and as strong and tasty as Swennen's bananas were, it wasn't enough. In Africa, Swennen noted, “We couldn't just look at resistance.” He'd come up with bananas that the disease completely passed over; the fruit would have gorgeous, eighteen-hand bunches—a feast growing on a single tree—but they were twenty-five feet high. That was an unexpectedly negative attribute, not because tall banana trees are susceptible to high winds—which is more of a problem in Central America—but because they were nearly impossible, in a primitive village, to pick. Another quality his bananas had to have was stiff, erect leaves, since bananas are part of a growing system that also includes cassava, cocoa, tobacco, and dozens of other crops and the canopy they provide helps to protect the entire garden plot from the sun. That was something else Swennen hadn't originally thought to breed for. Village fruit is part of a complex agricultural routine that may look haphazard to the average observer but which is in fact the result of generations of local trial and error. “When you're talking about a thousand years of tradition,” Swennen says, “anything you introduce had better work within that structure.”

It wasn't that Swennen didn't believe his bananas could, eventually, have these qualities. But, as with all conventional banana breeding before and after, it was taking too long to get results. “That's the banana's drawback—to get a real, wide-scale evaluation, it takes years.” With Black Sigatoka and other banana diseases advancing, time was something these tiny villages, and the rest of the world, was running out of.

In 1993 Swennen returned to Belgium. He still misses the adventure of the field, but he now believes that conventional breeding methods just won't cut it—that saving the banana is something that can only be accomplished in the lab.

CROSSBREEDING AND BIOTECHNOLOGY
are both forms of genetic manipulation. The first has been effective and widespread for thousands and thousands of years. Changing life-forms by directly manipulating their DNA, however, is such a new technology that most scientists believe only a tiny fraction of what needs to be understood about it has so far been discovered. Even so, industrial agriculture is exposing the public to such technologies (often without disclosure) with daily frequency. In 2000, 90 percent of the corn Americans ate was bioengineered, as were more than half the soybeans, according to the U.S. Department of Agriculture. Both numbers have increased since then.

The acronym GMO (genetically modified organism) is used as a blanket term for nearly all forms of food biotech, though it is technically less than accurate since genetic modification is also the basis of conventional breeding methods. Nevertheless, the term has stuck, and I will use it here instead of proposed but less familiar substitutes like transgenics,
GM foods,
or
GM crops
. Creating a GMO is a complex process. But the basics can be explained fairly simply: Genes from one organism that carry specific traits—resistance to a disease, increased size, or more rapid maturation—are added to the genetic material of another. The organisms can be vastly different, such as DNA from a bacterium added to tomatoes, or relatively similar, like crossing radishes with bananas (such a mixture is currently being studied for providing resistance to fusarium fungus).

The techniques are precise—microscopic tools make researchers in the field the modern equivalent of Swiss watchmakers—but the basics you learned in high school biology are the same. You'll recall that chromosomes are sort of a package for DNA; every living thing has a specific number of chromosome pairs—in nature, for the most part, one from each parent. Human-influenced crops can be different: A and B sequenced bananas can contain two or three sets of chromosomes. Cavendish contains three.

The DNA is arranged in the chromosome in wrapped strands. The commonly used analogy is a spool of thread; if a strand of human DNA was pulled straight, it would be about the height of Yao Ming, currently the tallest player in the NBA. If DNA is one of the “building blocks” of life—containing a blueprint for an organism's specific traits (like the ability to hear or see, or thickness of skin)—then the genes it is made up of are the workers that execute the blueprint by creating specific proteins that assemble to form the structure that supports the trait, whether on an individual level, to make hemoglobin, the protein that allows blood to carry oxygen through the body, or in concert, as multiple proteins gather to form an eye or an elephant or a banana plant. Sometimes genes mutate. A hemoglobin mutation causes sickle cell trait, and it was probably a mutation that initially yielded a seedless banana thousands of years ago.

Understanding genetic modification requires shifting the metaphor. Instead of a spool of thread, imagine that chromosomes are an old-fashioned film reel—the kind that used to jam up the projectors in that same biology class. The film wrapped around the reel is made up of individual frames. If the frames are genes, then creating a GMO involves splicing the genes from one movie, perhaps
Gone with the Wind
, into another—let's say
Star Wars
. The result is something that should contain the best qualities of both: Rhett Butler played by Harrison Ford and Scarlet O'Hara with a cinnamon-bun hairstyle.

If you're using handy, expensive lab toys, the cut-and-paste job isn't all that difficult. The hard part is determining which gene performs what function. That was the purpose of the human genome project—launched in 1990 and completed in 2003—that mapped the approximately 25,000 genes contained within the human body (the function of each and every gene is far from known, but having the map has allowed thousands of scientists around the world to begin individual and highly specialized efforts to determine and take advantage of that information).

Mapping of the banana genome was begun in 2001 by a consortium of twenty-seven publicly funded organizations in thirteen countries. The goal was to have the entire banana genetic sequence—using a wild Asian banana as the base material—decoded within five to ten years. The banana is only the third major crop to undergo gene sequencing. The first was rice—though rice lags behind wheat and corn in global consumption, there are more people absolutely dependent on it, as with the banana in Africa—completed in 2005. (Rice contains about 37,000 genes. The 25,000 found in Homo sapiens is double that in a fruit fly and about the same as in the Japanese
fugu
puffer fish; the seaborne creature's genes contain the recipe for a deadly toxin, which kills several hundred Japanese diners a year as they eat the fish, which has to be precisely sliced in order to avoid the poison in its liver and skin.)

The first concrete results of the banana genome project came in 2005, when researchers announced they'd mapped more than half of the banana's genes (the project is on track to be completed by the end of 2008). About five thousand of those genes were decoded by Brazilian scientists, who said they'd found twenty that could potentially be used to bestow disease resistance on cultivated bananas. That may sound like a small number, but that total has already made the process forty thousand times more efficient than the million-toone success rate yielded by the manual search for seeds required in traditional breeding.

IN THE DOCTOR'S OFFICE–LIKE BASEMENT
of the Leuven lab, I am looking directly at some of those genes—though without a microscope, they look like little more than a flask of water. Serge Remy, one of the Leuven researchers, is taking me on a step-by-step walk-through of the banana-manipulation process. The flask contains thousands of banana cells, derived from one of the 1,200 varieties cryogenically preserved at the Belgian facility; each cell can mature into a plant, using a process similar to the one that yields banana embryos at FHIA. But rather than simply growing these cells into baby bananas, Remy is using them as base material for what geneticists term
transformation
.

Though cut-and-paste is a good metaphor for the process, the actual procedure isn't done with an X-Acto knife and glue. Most modern transformation of plants, including bananas, is accomplished two ways. The first technique involves brute force: In a process called “particle bombardment,” tiny pieces of gold or tungsten are coated with DNA and blasted at high velocity into living plant cells or embryos. The shooting can be done with miniature air guns, mechanical devices (think of toy cannons), or via magnetic or electrical discharge. The most subtle and ingenious way to carry transforming material into a test organism is by using bacteria. Remy holds up the flask and taps on it, as if I could see what he's about to explain: “We use bacteria that are naturally found in soil,” he says. The bacteria carries the material with the desired trait into the host's DNA. The bacteria attaches itself to the cells and will (if it works; success isn't guaranteed) ultimately turn up—the formal term is
express
—in the growing plants. “It really is pretty neat,” Remy adds, pointing at the flask again. All I see is water, but I nod my head in agreement.