Wednesday, April 11, 2012

Look at all those hands!

Species name: Musa acuminata x balbisiana

Common name: Banana

Location: Panama

The genetic origin of bananas has only recently been discovered through DNA sequencing. Traditional views of the banana parentage say that there are about four distinct species of banana that we use in cultivation today, each species having been genetically modified through traditional breeding methods to arrive at roughly the same banana shape, colour, taste, and growth pattern. Each species would have referred to a different size banana, either a "traditional" banana, a finger banana, plantain, etc. Now we know that the banana we can buy in grocery stores in Canada is all one species, and its a hybrid of two wild ancestors. I should also mention that technically a "bunch" of bananas isn't really a bunch. If you want to sound all technical and fancy when you refer to your bundle of bananas, call them a "hand" as those "in the know" do.

To say that the banana we eat today is all one species isn't quite going far enough. Banana plants everywhere are actually all CLONES of each other, meaning that they are all genetically identical. The specific strain or variety of banana that we grow today is called the Cavendish banana. For those of you not in Biology or with a Biology background you might be thinking "so what? We got what we wanted out of the plant, and now we want it to stay how we like it. No big deal". Well, this is actually a huge deal. The banana plants that we grow today have no resistance to a recently discovered fungal strain called Fusarium TR4 (Tropical Race 4) which attacks the roots of banana plants. This has the potential to completely destroy the entire population of banana plants and so a lot of people recently have been saying that the common banana is at risk of going extinct. Then what? Well, then we have no more bananas. In the 1820s something similar happened to a variety of banana called Gros Michel, which was the most widely consumed variety of the time. This concept of complete devastation of an agricultural crop due to disease isn't new; we've been suffering with this problem as humans since we made the switch to an agricultural life almost 14,000 years ago.

What's special about bananas? Well, for one they don't have sex. This is incredibly unusual in the plant kingdom for a plant to not only reproduce parthenocarpally (in other words, each banana is produced from one female flower without the input of pollen from a male flower), but also to produce a large, fleshy fruit from this as a result. A second unusual trait about bananas is that they're not actually trees, despite how big they get. In order for a plant to have the potential to be a tree, it must produce a structure in its stem called a vascular cambium, which bananas cannot do. They might be tree-like, but they're not trees. Now you can correct everyone when you're visiting a banana plantation in a tropical country!