Banana-geddon! No more nanas! These are some of the headlines gracing tabloid newspapers at the moment. What's the story? Apparently, bananas are about to get wiped out and we'll have to eat more apples instead. Well… maybe not.
The real story is that two diseases are currently rampaging through banana plantations - but more on that later. First, the origin of bananas and just why we have a problem.
Bananas are thought to be one of the first fruit crops to ever have been cultivated, as far back as 15,000 years ago. The bananas we eat today come from mutant plant strains; the wild banana is a fruit that is largely inedible; the fruits are filled with large, hard black seeds, whereas the mutant strains have few or no seeds (remember that, because it's important for later on). These seedless mutants were carried to most regions around the world where bananas are commercially grown.
Most plants reproduce by means of sexual reproduction; a flower must be pollinated by pollen, usually (but not always) from another closely related species of plant. From this pollination, seeds are formed and eventually mature, and are spread by various means (wind, birds, animals), to new locations where they germinate and spread the plant. Because mutant strains of bananas have no seeds, they can't reproduce like this, and are therefore propagated by asexual methods; that is, usually the rhizome or root of the plant is split - technically small plants called suckers are formed, and they are removed from the parent plant and planted elsewhere.
This method of propagation results in bananas being genetically identical (sexual reproduction within a species introduces genetic diversity); all banana plants of the Cavendish variety are identical to another. Why is this a problem? All Gala apples, all Navel oranges, all King Edward potatoes are the same. Well, it's quite simple - we don't rely on just Gala apples to produce all the apples we eat or Navel oranges as our only oranges. We do however rely on Cavendish bananas for almost 100% of all bananas we eat in the Western World, and they're all genetically identical.
If the entire population of something is genetically identical, something that can attack and kill one member of that population can kill all of it; this is the same theory behind antibiotic resistance; in a population of bacteria, there will usually be some mutants that are resistant to antibiotics. Therefore, when penicillin or one of its variants is used to treat the bacteria, all the susceptible ones are killed and the resistant ones remain, with the resistant ones multiplying and becoming the only members of the new population.
With Cavendish bananas' it's the opposite way around; there are no mutants that are resistant to disease, and there are two big bad diseases attacking bananas; Black Sigatoka, and the dreaded Panama Disease.
Let's go back about 50 years, to the middle of the last century. Cavendish wasn't around much - the main banana grown for commercial purposes was Gros Michel. This was a banana that was apparently bigger and much tastier than Cavendish, but unfortunately it was susceptible to Panama Disease. For the gardeners reading this, Panama disease is also known as Fusarium Wilt of Banana (other species can affect cucumbers and melons), and is one of the nastiest of all plant diseases.
Panama disease is a fungal infection of the plant; it usually gets into a plant through its roots, and gradually works its way up into the stem, and then the leaves. The leaves rot, and the crown of the plant collapses, eventually killing it, but initially greatly reducing the fruit yield. There are several variants of Panama disease; Type 1 caused the eventual near extinction of Gros Michel.
Panama disease was first reported in Australia in 1876, but it took until the 1950s for it to spread around most of the world. It is now found in all banana producing regions except some islands in the South Pacific, the Mediterranean, Melanesia and Somalia. It spreads by several means; most commonly infected rhizomes (plants) are used to plant new plantations (the infection does not show in young plants) which instantly become infected, but it can also travel in water, soil, on tools and by human contact.
In the middle of the last century, its effect was devastating; between 1940 and 1960, 75,000 acres of banana plantations were destroyed in the Ulua Valley of Honduras, 10,000 acres was put out of use in Suriname in 8 years, and 15,000 acres in Costa Rica in 12 years; at the time, it cost between $800 USD and $2,000 USD to plant an acre of plantation, with an economically devastating effect.
However, instead of trying to solve the problem, the banana companies tried to avoid it, and millions of acres of rainforest were ripped up to replant with bananas. Obviously this couldn't carry on forever, and by 1960 many of the companies were nearly bankrupt.
Eventually it was recognised that a new variety would need to be planted, and billions of dollars was spent on altering farming and supply infrastructures to accommodate slightly different needs of the Panama disease resistant Cavendish banana compared to the Gros Michel. Plantations converted over, consumers accepted the new variety, which before now was little known, and all was well. Until now, that is.
While Cavendish is resistant to type 1 Panama Disease, in 1992 a new strain emerged, Type 4, that Cavendish is not resistant to (Type 2 affects cooking bananas such as plantain, and Type 3 does not affect bananas). Unfortunately, Type 4 also affects many other banana strains, including plantain.
Type 4 was first discovered in Asia, and since then it's burned through plantations in Indonesia, Malaysia, Australia and Taiwan, and is currently on its way through Southeast Asia. It hasn't yet reached Africa or Latin America, and opinion is divided on whether it will in 5 years or 10 years, but it's pretty much agreed it will come eventually, and it will come faster than in the 1950s, due to much improved world travel and infection possibilities (anywhere on the planet is now within reach of everywhere else within 24 hours thanks to the global air network).
How do we fight it? Well that's easier said than done. Several chemical treatments work, but they only kill off the fungus for a certain amount of time; cleaned plantations are usually reinfected within three years at most due to the veracity of the disease and limited controls available.
The other thread is another disease called Black Sigatoka. This is a leaf spot disease that affects bananas, reducing yield by up to 50% in infected plants. It's a fungal disease that greatly favours the hot warm tropical weather bananas require to grow, and is very difficult and expensive to control through the use of pesticides; like panama disease, it's starting to become resistant.
On their own, neither disease would be a species killer, but with both together, bananas are in for one hell of a fight. Work is currently being carried out on two fronts; GM and none GM.
Bioengineers are working with the decoded Banana genetic genome, manipulating the chromosomes and trying to introduce characteristics such as disease resistance into certain varieties. However, they acknowledge that the genetic modification angle may put a good deal of people off from eating them.
On the other side of the fence, botanists such as Juan Fernando Aguilar are using traditional crossing methods in an attempt to breed new species of bananas through crossing them; a long laborious process. The Honduran Foundation for Agricultural Investigation (FHIA) is one of these groups of people, run by Aguilar. With a growing area the size of a football pitch, they are currently trialling over 300 varieties of banana. It's not an easy job; the staff have to hand pollinate bananas, whilst all the time keeping track of their activity.
From pollination, it takes about four months for the fruit to ripen, after which it is harvested and taken for seed extraction. Not many are found - about one seed for every 300 bananas, and of this tiny number of seeds, only about a third germinate, so you can see just how big a task they have in front of them - from seed to fruit takes roughly two years, and few so far have met even several of the many desired characteristics. One of the most successful to date looks like a banana, but tastes like an apple!
This entire story is a bit of a hot one at the moment - tabloid newspapers are proclaiming the death of bananas, but it won't be. "We could be paying 10 times what we are now this time next year!" No, we won't be. Yes, there is a problem, several in fact, but it's not as severe as the newspapers want us to think. Banana plantations deal with these diseases on a daily basis, and the new strain of Panama disease hasn't reached Central and South America (the two biggest regions for export) or Africa yet.
But still, there's a constant fight to save our bananas. One thing is for sure - there will be bananas in our future, but of what type, we don't know. Ten years from now, we could be chopping up a red banana into our dessert, or packing a blue java banana in our lunchbox. Should be interesting!