Scientific breakthrough could save the banana from extinction

Genetic experiments find ‘key factor’ in Panama Disease fungus which threatens to wipe out the fruit

The banana could be saved from extinction after scientists made a key breakthrough in the battle against a fungus that threatens to wipe out the fruit.
Panama Disease is a fungal infection, also known as Fusarium oxysporum, that emerged in the 1990s and affects the main variety of banana eaten globally, the Cavendish banana.
Scientists have now discovered genes in the pathogen which produces more of a chemical called nitric oxide. It is thought this is what makes the infection so severe.
Experiments that removed two genes from the fungus reduced the disease’s potency, the scientists found. They hope that by exploiting this they can find a treatment for the disease.
The UK imports more than half a billion tonnes of bananas annually and is one of the biggest markets for the crop, which is grown predominantly in tropical climes such as Ecuador, Costa Rica and Côte d’Ivoire.
Modern bananas are at high risk of disease and extinction because all Cavendish bananas are clones descended from a plant created in the 1950s in the greenhouses of Chatsworth House, in Derbyshire.
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Cavendish bananas were created after another type of Panama Disease wiped out the previously dominant species, the Gros Michel, also known as the Big Mike.
“The kind of banana we eat today is not the same as the one your grandparents ate,” said Prof Li-Jun Ma, a biochemist at the University of Massachusetts Amherst.
“Those old ones, the Gros Michel bananas, are functionally extinct, victims of the first Fusarium outbreak in the 1950s.”
Analysis of the fungus revealed it has accrued “accessory genes” at the end of some chromosomes which make it so potent.
Experiments found these genes increase the amount of nitric oxide in the plant itself, which disrupts how it moves nutrients around and causes leaves to yellow and wither.
Prof Ma said the production of extra nitric oxide is “the key factor” in why the fungus threatening the Cavendish banana is so severe.
The scientists gathered 36 different strains of the fungus from around the world, including ones known to target the old Big Mike variety as well as the modern crop.
“Identifying these accessory genetic sequences opens up many strategic avenues to mitigate, or even control, the spread of [Panama disease],” says study lead author Dr Yong Zhang.
The study discovered the type of disease that decimated bananas in the 1950s is not an ancestor of the current strain, despite it being the same type of fungus.
Other staple crops such as the potato, cocoa and coffee are also struggling with the threat posed by either disease, climate change or other pressures.