Banana under threat
Jan 18, 2003
The commercial banana has such a narrow genetic base that within a decade the plant could be wiped out by two fungal diseases that are rampaging through Central America, Africa and Asia, New Scientist says.
The commercial banana has such a narrow genetic base that within a decade the plant could be wiped out by two fungal diseases that are rampaging through Central America, Africa and Asia, New Scientist says.
The British weekly says the alarm for the world’s most popular fruit has been sounded by a Belgian plant pathologist, Emile Frison, top researcher at a worldwide network of banana specialists, INIBAP.
If Frison’s doomsday scenario comes true, it will not just mean inconvenience for shoppers in western countries who are deprived of their favourite fruit.
It would also spell poverty or starvation for half a billion people in tropical countries who depend on bananas for food or income, the equivalent of the Irish potato famine, in which a tuber blight decimated the population of Ireland in the mid-19th century.
In a report due to be published in Saturday’s issue, the British weekly says the problem with the banana eaten around the world today is that it is drawn from a tiny gene pool.
“That uniformity makes it ripe for disease like no other crop on Earth,†it warns.
Just one variety, a type called Cavendish, accounts for almost all of the bananas sold in the world today.
The reason for this is because the Cavendish, like other commercially-grown bananas, is a genetic freak.
In its wild form, the banana is almost inedible, for it is riddled with stoney seeds.
The theory goes that early hunter-gatherers must have stumbled across rare mutant plants that produced seedless, edible fruit, the forefather of today’s commercial varieties.
These soft-fruited plants are the result of a genetic accident that gives their cells three copies of each chromosome instead of two.
That imbalance prevents seeds and pollen from developing normally, making the mutant plants sterile. Banana plants are grown by replanting cuttings from a parent plant.
Traditional varieties of sexually reproducing crops have a much broader genetic base, in which genes swap and recombine in each new generation, and the new configurations offer a better chance against disease.
Bananas, though, have no such defences. They are under attack on two fronts, and on present trends could disappear within 10 years, according to Frison. The first threat is a fungal disease called black Sigatoka, which has become a global epidemic since it first appeared in Fiji in 1963.
To keep this killer at bay, commercial growers typically spray plants 40 times a year — but, says Frison, this is a losing battle, for the fungus is swiftly developing resistance to chemicals. In any case, expensive fungicides are out of reach for poor farmers.
The other is a new form of relentless soil fungus called Panama disease that 40 years ago wiped out the then dominant variety, Gros Michel. Fields with Panama fungus remain unusable for years, even if they are doused with fungicise.
Two potential avenues open up for resolving the banana crisis, says New Scientist.
Efforts to come up with a new variety have been largely thwarted because all of the edible varieties of banana are vulnerable to the two diseases.
After an extraordinary effort, breeders at the Honduran Foundation of Agricultural Researchers, exploited a genetic quirk of the edible banana in which it very occasionally allows an almost normal seed to develop and produced a cross-breed.
The result — a seedless edible banana that is resistant to both kinds of pest — is not a hit, for many complain that it tastes more like an apple than a banana.
The second option is genetic modification: to introduce a gene from a wild species that would make a variety of disease-resistant edible bananas.
Ecologists are strenuously against genetically-modified crops, saying the long-term impact on health and the environment are unknown.
But bananas might be considered an exemption, given the huge importance of this crop in poor countries and the fact that bananas are sterile, which reduces the risk that the inserted genes could spread to wild relatives or other species.
AFP
The British weekly says the alarm for the world’s most popular fruit has been sounded by a Belgian plant pathologist, Emile Frison, top researcher at a worldwide network of banana specialists, INIBAP.
If Frison’s doomsday scenario comes true, it will not just mean inconvenience for shoppers in western countries who are deprived of their favourite fruit.
It would also spell poverty or starvation for half a billion people in tropical countries who depend on bananas for food or income, the equivalent of the Irish potato famine, in which a tuber blight decimated the population of Ireland in the mid-19th century.
In a report due to be published in Saturday’s issue, the British weekly says the problem with the banana eaten around the world today is that it is drawn from a tiny gene pool.
“That uniformity makes it ripe for disease like no other crop on Earth,†it warns.
Just one variety, a type called Cavendish, accounts for almost all of the bananas sold in the world today.
The reason for this is because the Cavendish, like other commercially-grown bananas, is a genetic freak.
In its wild form, the banana is almost inedible, for it is riddled with stoney seeds.
The theory goes that early hunter-gatherers must have stumbled across rare mutant plants that produced seedless, edible fruit, the forefather of today’s commercial varieties.
These soft-fruited plants are the result of a genetic accident that gives their cells three copies of each chromosome instead of two.
That imbalance prevents seeds and pollen from developing normally, making the mutant plants sterile. Banana plants are grown by replanting cuttings from a parent plant.
Traditional varieties of sexually reproducing crops have a much broader genetic base, in which genes swap and recombine in each new generation, and the new configurations offer a better chance against disease.
Bananas, though, have no such defences. They are under attack on two fronts, and on present trends could disappear within 10 years, according to Frison. The first threat is a fungal disease called black Sigatoka, which has become a global epidemic since it first appeared in Fiji in 1963.
To keep this killer at bay, commercial growers typically spray plants 40 times a year — but, says Frison, this is a losing battle, for the fungus is swiftly developing resistance to chemicals. In any case, expensive fungicides are out of reach for poor farmers.
The other is a new form of relentless soil fungus called Panama disease that 40 years ago wiped out the then dominant variety, Gros Michel. Fields with Panama fungus remain unusable for years, even if they are doused with fungicise.
Two potential avenues open up for resolving the banana crisis, says New Scientist.
Efforts to come up with a new variety have been largely thwarted because all of the edible varieties of banana are vulnerable to the two diseases.
After an extraordinary effort, breeders at the Honduran Foundation of Agricultural Researchers, exploited a genetic quirk of the edible banana in which it very occasionally allows an almost normal seed to develop and produced a cross-breed.
The result — a seedless edible banana that is resistant to both kinds of pest — is not a hit, for many complain that it tastes more like an apple than a banana.
The second option is genetic modification: to introduce a gene from a wild species that would make a variety of disease-resistant edible bananas.
Ecologists are strenuously against genetically-modified crops, saying the long-term impact on health and the environment are unknown.
But bananas might be considered an exemption, given the huge importance of this crop in poor countries and the fact that bananas are sterile, which reduces the risk that the inserted genes could spread to wild relatives or other species.
AFP