They're in trouble. Can biotechnology save the fruit?
May 30, 2008
The linkurl:banana;http://www.the-scientist.com/2007/3/1/74/1/ we eat today is not the one your grandparents ate. That one - known as the Gros Michel - was, by all accounts, bigger, tastier, and hardier than the variety we know and love, which is called the Cavendish. The unavailability of the Gros Michel is easily explained: it is virtually extinct.Introduced to our hemisphere in the late 19th century, the Gros Michel was almost immediately hit by a blight that wiped it out by 1960. The Cavendish was adopted at the last minute by the big banana companies - Chiquita and Dole - because it was resistant to that blight, a fungus known as linkurl:Panama;http://www.the-scientist.com/article/daily/53628/ disease. For the past fifty years, all has been quiet in the banana world. Until now.
__Panama disease in Hawaii__
__Photo: Scot Nelson__
Panama disease - or linkurl:__Fusarium__;http://www.the-scientist.com/news/display/52853/ wilt of banana - is back, and the Cavendish does not appear to be safe from this new strain, which appeared two decades ago in Malaysia, spread slowly at first, but is now moving at a geometrically quicker pace. There is no cure, and nearly every banana scientist says that though Panama disease has yet to hit the banana crops of Latin America, which feed our hemisphere, the question is not if this will happen, but when. Even worse, the malady has the potential to spread to dozens of other banana varieties, including African bananas, the primary source of nutrition for millions of people.linkurl:Crop disease;http://www.the-scientist.com/article/home/53408/ is only half the problem. The other part is denial. One of the most recent places Panama disease struck was linkurl:Australia.;http://www.the-scientist.com/article/display/21927/ Three years ago, when I was researching my book on bananas, growers down under were bragging that they'd found a way to control the disease, which first appeared in 1997 near the Northern Territory town of Darwin. "We have developed a rapid and accurate DNA-based diagnostic test...used in the detection and management of outbreaks," asserted a brochure issued by the country's Cooperative Research Centre for Plant Protection.
The Australian management program consisted of quick quarantine of fields that were proven by the test to be infected. But early detection doesn't necessarily buy enough time. The plan came apart in March 2006, when Cyclone Larry ravaged Australia's banana growing regions. High winds destroyed more than 85% of the banana crop, and flooding spread infected water and dirt to the surviving banana trees. An October linkurl:report;http://www.abc.net.au/news/stories/2007/10/17/2061762.htm from the Australia Broadcasting Company documented the rapid spread of the blight on previously-disease free plantations. Reporter Anne Barker wrote that the "industry, which once had such bright prospects, is now facing collapse." Panama disease hasn't hit our hemisphere yet, and the big banana companies appear unalarmed. Chiquita's 2006 annual report doesn't mention banana disease at all. The company's 2007 end-of-year SEC filing names plant disease as a "risk factor," but only mentions linkurl:black sigatoka,;http://www.ipm.iastate.edu/ipm/hortnews/2005/3-23-2005/banana.html which can be controlled chemically.Why should it be? After all, Latin America, where we grow all of our bananas, is a hemisphere away from the places where the disease is now spreading. With all that ocean, could the epidemic could actually reach our bananalands? Not only is it possible, it might already be happening. In late December, 2007, Philippine agriculture secretary linkurl:Arthur Yap;http://www.op.gov.ph/profiles_yapDA.asp announced that the U.S. had agreed to import a large shipment of Cavendish bananas from Philippine plantations (overall, we import about 8.5 billion pounds of bananas each year, all from Latin America).
__Transgenic plants in field, Uganda__
__Photo: Andrew Kiggundu__
Panama disease is so virulent that a __single clump of dirt__ tracked in on a tire tread or a shoe can spark a country-wide outbreak. It isn't hard to imagine that a stray banana box from the Philippines, loaded into a Dole shipping container could be left unloaded at Long Beach, California, and continue on to Guatemala, where it could infect that nation's crop and tear through Latin America. In fact, the original Panama disease outbreak that decimated the Gros Michel almost certainly went from Asia, to the Caribbean, to Central and South America, though the exact path was never determined. The spread of Panama disease from Asia to the banana plantations of the Western Hemisphere is more than imaginable. With shipping containers traveling the world, and bananas crossing hemispheres, it's likely. When the first outbreak of Panama disease hit the Gros Michels of South and Central America, it nearly put the entire industry out of business. Only at the last minute was a substitute banana - the Cavendish - found. The Cavendish was thought to be resistant, and for 50 years, that was true. No longer.
__Transgenic banana plantlet in Belgian lab__
__Photo: Dan Koeppel__
Now, the future of the Cavendish lies in genetic engineering. Scientists are on the way to creating bananas that resist Panama disease in the lab. The problem with these engineered bananas, aside from the fact that they have not yet definitively shown resistance to the disease, is that they lack the other characteristics - ideal ripening speed, a thick skin, and the right taste - that make a banana variety attractive for export. Making a single banana with all of those attributes may take years. Another issue is consumer acceptance: surveys have shown that most shoppers would reject modified bananas, even if they were proven to be safe.Bananas are, however, excellent candidates for genetic modification. They are sterile - no seeds or pollen by which mutations might spread - and reproduce vegetatively. Right now, regulations have prevented even publicly funded research organizations from testing more than a handful of transformed bananas in the field. Most of this research has been conducted under the auspices of linkurl:Bioversity International,;http://www.bioversityinternational.org/ an umbrella group that works mostly on food security issues. The bananas being field tested were developed though a collaborative effort between Ugandan and Belgian scientists in Leuven, Belgium, and are being grown at experimental plots in linkurl:Uganda,;http://www.the-scientist.com/2007/9/1/65/1/ a country where about 80 percent of some local diets is made up of the fruit, and where the consequences of a banana wipe-out would be disastrous. The millions of people like those in Uganda who depend on bananas to survive would be the real beneficiaries of a better banana.There's little time left. If there is a "grail banana," it is likely to be found in the lab. The question is whether we'll let it split from there.__Dan Koeppel is the author of__ linkurl:Banana: The Fate of the Fruit That Changed the World.;http://www.amazon.com/Banana-Fate-Fruit-Changed-World/dp/1594630380/ref=sr_1_1/102-4278750-1581759?ie=UTF8&s=books&qid=1193688240&sr=1-1 __He spent three years hanging out with banana growers, scientists, and banana consumers around the world. His website is linkurl:www.bananabook.org.__;http://www.bananabook.org/Dan Koeppel email@example.com__Corrections (June 3): The original version of this article stated that scientists have created bananas resistant to Panama disease. This has been changed to reflect the fact that definitive tests for Panama disease resistance have not yet been conducted. Also, this article originally said that bananas developed by scientists in Leuven, Belgium were being field tested. While the bananas being tested were indeed developed in Belgium, it was a Ugandan scientist, Geoffrey Arinaitwe, who made the plants as part of a broader collaboration between several groups. Finally, the photo credit for the Ugandan banana field incorrectly read "Rony Swennen." __The Scientist__ regrets these errors.__