Tuesday, April 24, 2012

The Future of Bananas

This is what bananas looked like before humans got involved in their reproduction.

Some of you may know that 50 years ago, although people in the USA were eating bananas, they were a different kind than the ones you're familiar with. That's because at the time, the Gros Michel was the type of banana gown for eating, and almost all bananas for sale were this type, grown on clonal trees. A post over at BoingBoing explains what happened to these bananas, and what will likely happen to the bananas we're enjoying now. (This post was inspired by another at Damn Interesting, also about the sex life of bananas. Go check it out.)

Because we don't like to eat bananas with seeds, humans have selectively bread bananas without them. (The picture above is of a wild banana that has not been subjected to selective breeding by humans.) Unfortunately for the bananas, this makes it difficult to reproduce. Humans make more banana trees by growing a new tree from a cutting of an existing one. This creates a population of banana trees that are all genetically identical - the entire code of their DNA is the same. If these banana trees were human, they would all be identical twins.

In the same way that two humans may not be affected by a disease in the same way, diseases also affect banana trees differently. This variation is due to small differences between individuals. By creating a clonal population of banana trees, we have eliminated this variation. If a disease kills one of these trees, it will kill all of them. This is what happened to the Gros Michel, and it's why you can't find this type of banana anymore. It was wiped out by a fungus known as Panama Disease in the 1950's.

The banana you know today, the Cavendish banana, replaced the Gros Michael after that period. However, the Cavendish today has the same problem the Gros Michael had 50 years ago - they are all clonal plants. A disease called Black sigatoka is laying siege to the Cavendish, and it may not be long before the entire population is wiped out by this disease.

Don't worry too much about future bananas, though. There are many, many varieties of bananas grown around the world, and banana growers have already developed a banana, the Goldfinger, that is resistant to Black sigatoka. These bananas are also a clonal population, so it doesn't mean that they won't be in danger of being wiped out by another disease. The banana-disease arms race will likely continue on into the future, but until then maybe you (or your children) will come to recognize the Goldfinger as your friendly neighborhood banana.

(Image: Inside a wild-type banana, Creative Commons Attribution 3.0 image by Warut Roonguthai)

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