Grow Exeter | Apr 17, 2019 | 0
The banana is dying. Yes, you read that right. The race is officially on to reinvent the banana before it’s too late.
There are 1000 varieties of banana out there; a fact I was very surprised to learn when researching this article. The most popular variety, the Cavendish, named after a British nobleman who grew the exotic fruit in his greenhouse, accounts for almost the entire export market. It accounts for 47 per cent of all global production of the fruit. As a country, we import five billion bananas a year. We are used to this seemingly endless supply of the relatively cheap and versatile fruit. But what we probably didn’t know is that the banana industry is as fragile as its phloem bundles (those annoying little strings on a banana).
Up until recently, the Cavendish banana plant has been a relatively perfect crop to grow; it is sterile and reproduces by creating clones of itself, it’s short so it doesn’t blow away easily in hurricanes, it’s easy to spray with pesticides and it reliably produces lots of bananas.
Everything was coming up bananas, until 1989 when Dr Randy Ploetz received a package from Taiwan in his Miami lab. This was not an unusual occurrence for Dr Ploetz, who holds a doctorate in plant pathology and was collecting banana diseases. Gazing down through his microscope eyepiece, Dr Ploetz realised that this Taiwanese pathogen was unlike anything he’d encountered before. After sending the specimen for testing, he discovered that it was Tropical Race 4 (TR4). This fungus lives in the soil, is impervious to pesticides and kills banana plants by choking them of water and nutrients. In a nutshell, bad news for bananas. Worse news? TR4 only affects a particular type of banana. Yep, you’ve guessed it. The Cavendish.
Ploetz continued to receive packages containing TR4 from plantations in other countries, including Malaysia and Indonesia. He says:
“At the time all we knew was that it was a new pathogen. We didn’t know what to expect as far as its broader implications. The more samples we got from these export plantations, the more we began to realise that this was a bigger issue than we had ever anticipated.” (Wired)
In 2013, TR4 was discovered for the first time in Mozambique. The pathogen had now travelled to many countries, including Israel, India and Australia. Like a stealthy assassin, TR4 can live undetected in the soil for decades but when it hits, the destruction it causes is near total. Ploetz describes it as “It looks like somebody’s gone to the plantation with a herbicide.”
The Cavendish’s genetic uniformity, which previously had made it the love of banana growers, has now become its curse. With no TR4 resistant banana available and the fungus rapidly spreading towards Latin America, which grows almost all of the world’s export bananas, the future of the banana is in severe jeopardy.
In response to this bananas crisis, researchers are racing to use gene-editing to create a better banana, and most importantly, a TR4 resistant banana. The path through the plantation won’t be a smooth one though. The researchers face limitations of technology but their main resistance stems from lawmakers, environmentalists and consumers who are wary of GM crops.
Hope for the banana currently grows in Humpty Doo. No, I didn’t make that up. The small town is in Australia’s sparsely populated Northern Territory, where TR4 is in virtually all of the banana growing areas. With most plantations shut down due to the epidemic, one banana field is thriving. The world’s only TR4 resistant Cavendish bananas are succeeding while their relatives waste away beside them.
James Dale, a professor at Queensland University of Technology, dug up the way to create TR4 resistant bananas. In 2004, he isolated a simple gene from a wild banana. Although inedible, the Musa acuminata malaccensis has, drumroll please, natural immunity to TR4. Dale isolated the resistance gene (RGA2 if you’re a banana fan) from the wild banana and implanted it into a Cavendish plant. It was then that Dale hit a stumbling block:
“We weren’t allowed to take the fungus from the Northern Territory into our glasshouses.” (Wired)
Dale had no way to test if his GM bananas would resist the fungus due to Australia’s strict bio-quarantine rules. Luckily, help came along in the form of plantation owner Robert Borsato. His plantation opened in Humpty Doo a year before TR4 was detected. By the late 2000s, Borsato’s farm was overrun with the disease. He had heard of Dale’s research and turned to him for help.
Dale’s three year trial ended in 2015, but it was two more years before he published his results in the journal Nature Communications. With the success of his first trial, Dale has launched another study in Humpty Doo with an area ten times larger than the original site. He hopes to see the edited Cavendish on sale by 2021.
Despite this success, Dale’s bananas have yet to pass one simple, yet essential, test. He hasn’t eaten a single one. The terms of his trial license prohibit anyone from tasting the fruit. So what happens to all of those TR4 hardy bananas?
“We actually have to squish them up and use them as mulch,” Dale says.
So these one-of-a-kind bananas are turned into fertiliser. Now that’s bananas.
If Dale’s bananas continue to succeed, he aims to apply for a tasting license and then bring the bananas to the market. As Australia bans the import of fresh bananas, the government may be forced to choosing between GM bananas or lifting its import restrictions. That, or go without bananas. Option three just doesn’t bear thinking about.
Outside of Dale’s trials in Australia and Uganda, the future of the banana looks pale. Only 64 GM crops are approved for sale in the EU and there isn’t a single banana amongst them. So folks, it’s time to release you inner minion and go bananas over bananas while you still can.
And finally, geek points will be awarded to the reader who can tell me how many banana-related puns I have managed to dig into this article.