Love them or loathe them, bananas are one of the world’s most popular fruit. But a combination of the climate crisis and new killer diseases have had growers concerned over the banana’s threatened extinction, something that would impose a huge toll on farmers in countries from Guatemala to Malawi, alongside eradicating a staple food. Now researchers say they have made fresh advances in the race to save them from disaster.
This month, Yelloway – a research collaboration between Chiquita, the world’s largest banana company, and the crop-improvement company KeyGene – announced it had developed a fully fertile Cavendish banana, meaning it may be possible, through cross-breeding, to create new banana varieties that are commercially viable and resistant to disease. Second only to the tomato in terms of fruit consumption globally, the world grows about 139m tonnes of bananas a year. While there are more than 1,000 varieties, it is the Cavendish that is now found in most fruit bowls, taking over from the Gros Michel cultivar, which fell victim to Panama disease from the 1950s.
But the Cavendish itself is under threat from diseases including a strain of Panama known as Tropical Race 4 (TR4). Dr Jose De Vega, an expert on crop genomics at the Earlham Institute in Norwich, said TR4 had spread from south-east Asia to Australia, Africa, the Middle East and Latin America. Cavendish bananas have three sets of chromosomes, meaning they are typically sterile.
There are several different types of Cavendish, including dwarf versions, which have arisen as a result of random mutations in the Cavendish genome. But in each case new plants are grown from offshoots, so they are virtually genetically identical to the plant from which they came. While this results in uniform fruit, it also means they are vulnerable to the same diseases.
Peter Stedman, Chiquita’s sustainability director, said: “We are not trying to preserve Cavendish. We’re trying to replace Cavendish because we believe at the core of any sustainable farming system is biodiversity and genetic diversity.” Other researchers have taken different approaches. In Australia, a team at Queensland University of Technology led by Prof James Dale has created a genetically modified Cavendish by using a bacterium to introduce a gene from a wild banana that produces resistance to TR4.
The upshot, a type of Cavendish called QCAV-4, has been approved for human consumption in Australia and New Zealand, with researchers confirming that it tastes like the traditional banana. De Vega, by contrast, is collaborating with other researchers to explore gene-editing techniques. These involve using “molecular scissors” to cut parts of the Cavendish’s DNA and replace them with genes from other banana cultivars.
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