Slipping Away

The banana is America's number one fruit, in fact the average American eats approximately 25 pounds of bananas per year, more than any other fresh fruit. But that is all likely to change very soon; the banana as we know it is headed towards extinction. The culprit is a soil fungus that causes Panama disease (Fusarium wilt) which slowly kills the plant by blocking its xylems. Without these water transporting pathways it is only a matter of time until the plant wilts and dies.

The bananas we eat today represent only a fraction of the thousands of banana species that have grown around the world. Bananas were first cultivated in southeast Asia, but different varieties were brought to Africa and then South America. In the process many species were lost as only a few varieties were cultivated commercially. By the 1900s the choice banana of the Americas was "El Gros Michel." However in the 1960s, Panama disease began to wreak havoc on Big Mike; it was a banana apocalypse. Luckily a replacement was found in the smaller but nonetheless delicious Cavendish, which was resistant to the fungus. Since cultivated bananas do not reproduce sexually on their own and plants can yield fruits for many years, the genetic makeup of the Cavendish is virtually identical across the globe. The Cavendish runs the banana world, but trouble has been brewing in the banana community.

Recently, a new strain of Panama disease called Tropical Race 4 (TR4) has began to kill off the once heroic Cavendish. It is slowly spreading around the world through contaminated plants and shipping containers. It is no longer a matter of if... but when. The fact that cultivated bananas do not reproduce sexually and that the Cavendish is almost 100% seedless makes it very difficult to crossbreed plants. This limited genetic variation will prove to be the ultimate downfall of the Cavendish as the only known defense against Panama disease is genetic resistance.

There will be a hole in the hearts of many Americans when the banana is no more, but the real problem is that Panama disease affects many species of African bananas. These bananas, which function more like potatoes, are the staple food of many of the people living in the area around Lake Victoria. The effect of the eminent banana pandemic will be extremely profound. For this reason scientists are vigorously searching for genetically resistant bananas. Laboratories around the world have been combining rare and feral banana species but no delicious, high-yielding and most importantly resistant species has been created yet.

I first heard about this when I was reading this National Geographic article a couple of months ago.

Barker, C. L. Conservation: Peeling away. National Geographic Magazine, November 2008.

Calin Darabus (2)

UPDATE:

 No one is really sure when the Cavendishes will disappear but most people estimate that they will be gone within the next ten years. Malaysia was once a large grower of bananas but within five years of TR4 hitting all the plantations were destroyed. There are greenhouses and laboratories around the world that have isolated varieties of bananas growing (there are over 1000 varieties), so the bananas will never really become extinct but they will never be able to grown commercially. The good news is that the banana genome has been entirely mapped, so scientists have the tools they need to engineer some resistant bananas. Hopefully they will find some results soon. I hope that all of you keep up with this, because its really very interesting and I know bananas have a spot in all our hearts.