Biotech is bananas
Fruit crops under threat from fungus
We expect to have more than one variety of apple to choose from. Even at the most modestly stocked produce stand, you’re likely to see mounds of Galas, McIntoshes and Honeycrisps. When it comes to the banana, though — no matter where you shop — there’s only ever one: The Cavendish.
As far removed as we are from tropical growing regions, you’d be forgiven for assuming the fruit we recognize as a cheap and reliable staple is the one true banana. In reality, however, there are over a thousand types, each exhibiting a different flavour profile, texture, shape, colour, ripening pattern and durability. And for the second time in recent history, the very existence of the sole breed we rely on — which represents the single most exported fresh fruit on the planet — is under threat.
Researchers, seeking a solution, are looking towards a new form of genetic modification. Could specific alterations of the genetic makeup of the Cavendish help stave off the disappearance of such a critical commodity?
In August, Colombia declared a state of emergency when scientists confirmed a banana-killing fungus had reached the Americas for the first time. Known by its common name, Panama disease, the strain of fungus Fusarium oxysporum cubense — Tropical Race 4 (TR4) — has been a known issue since the early 1990s, but until this year, it was largely contained to Asia. Immune to pesticides, the lethal soil-borne organism, for which there is no known cure, obliterates yields by choking banana trees of essential water and nutrients.
The Cavendish’s predecessor as world’s presiding banana was the Gros Michel, a variety that dominated fruit stands in temperate regions until it was decimated by fungal strain Tropical Race 1 in the 1950s. That the extreme monoculture approach replicated with the Cavendish would result in a similar fate should have seemed inevitable.
Cavendish bananas are sterile and breeding them requires a cloning process that creates genetically identical plants. Because of their inherent lack of biodiversity, monocultures such as this banana are especially vulnerable to diseases and pests; when there’s a weakness, such as little or no resistance against TR4, it can have sweeping and ruinous effects.
Given the banana’s immense importance to producers and consumers, researchers have been attempting a variety of methods to create a resistance to the deadly fungus. According to the journal Nature, James Dale, a biotechnologist at Queensland University of Technology in Brisbane, is currently field testing genetically modified bananas in Northern Australia with some success. Dale has added a gene from a wild banana into the Cavendish variety that makes it more resistant to the TR4. However, even if scientists are able to breed a TR4-immune Cavendish, they wouldn’t be permitted to grow or sell them in a significant portion of the world. In Europe, for example, GM crops are restricted. And in Canada, although GMOs have been on the market since the late 1990s, nearly 90 per cent of Canadians believe they should be subject to mandatory labelling.
As a result, researchers like Dale and Leena Tripathi, from the International Institute of Tropical Agriculture in Kenya, have begun experimenting with CRISPR technology. Where GMOs have a foreign gene inserted into the organism, CRISPR allows for the organism’s genes to be edited. In the case of Dale, he’s discovered a dormant gene in the Cavendish he hopes to activate.
The technique is perhaps best described by Jennifer Kuzma, co-director of the Genetic Engineering and Society Center at North Carolina State University. In an interview with podcast Gastropod, she likened DNA to a book and CRISPR to a pen: “You can go in and you can edit the letters in a word, or you can change different phrases, or you can edit whole paragraphs at very specific locations.”