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Disappearing Bananas
The bananas we know today all originate from Musa acuminata, a wild, spindly banana plant native to the South East Asian islands that make up modern-day Indonesia, Malaysia and Papua New Guinea. The evolution of banana has been traced back to 10,000 years by agricultural experts. It has been at an evolutionary standstill ever since it was first propagated in the jungles of South-East Asia at the end of the last ice age. Normally wild bananas produce tiny fruits filled with hard seeds that make the fruit virtually inedible. But now and then, hunter-gatherers must have discovered rare mutant plants that produced seedless, edible fruits. Genetics now know that most of these edible plants are mostly results of accidental mutation that gave their cells three copies of each chromosome instead of two. This alteration prevents seeds and pollen from developing normally, rendering the mutant plants sterile, which is why scientists believe the world’s famous fruit (banana) could disappear forever in 10 years’ time as it lacks the genetic capability to ward off pests and diseases that are in Central America, Africa and Asia.
The banana needs a pick-me-up fast. But science has so far let it down. For decades plant breeders have all but ignored it, because developing new varieties without the help of sexual reproduction is expensive and time-consuming. As a result, most people in the developed world eat just one variety. In some ways, the banana today resembles the potato before blight brought famine to Ireland a century and a half ago. But it holds a lesson for other crops, too, says Emile Frison of the International Network for the Improvement of Banana and Plantain in Montpellier, France. Frison explains, “The state of banana can teach a broader lesson: the increasing requirements of food crops around the world is threatening their ability to adapt and survive.”
The unproductive hybrids were cultivated by the first men. They were planted by replanting their cuttings from their stem. And descendants of the results of those plantings are the bananas we eat today. Each is a virtual clone, almost devoid of genetic diversity. And that uniformity makes it ripe for disease like no other crop on Earth. Traditional varieties of sexually reproducing crops have always had a much broader genetic base, and the genes will recombine in new arrangements in each generation giving them enough resist the ability to fight pests and diseases. But that advantage is fading fast with the repeated plantation of high yielding varieties by planters. Plant breeders work tirelessly to maintain the resistance of standardized crops because even yields of the most productive crop could just nose dive, so they have to keep everything in check at all times. Even the director of the Rome-based International Plant Genetic Resources Institute, Geoff Hawtin says “When some pest or disease comes along, severe epidemics can occur.”
Banana is an interesting case study. Until the 1950s, one variety, the Gros Michel, dominated the world’s commercial banana business. Found by French botanists in Asia in the 1820s, the Gros Michel was by all accounts a fine banana, richer and sweeter than today’s standard banana without the latter’s bitter aftertaste when green. But it was vulnerable to a soil fungus that produced a wilt known as Panama disease. “Once the fungus gets into the soil, it remains there for many years. There is nothing farmers can do. Even chemical spraying won’t get rid of it,” says Rodomiro Ortiz, director of the International Institute for Tropical Agriculture in Ibadan, Nigeria. So, plantation owners played a running game, abandoning infested fields and moving to “clean” land - until they ran out of clean land in the 1950s and had to abandon the Gros Michel. Its successor, and still the reigning commercial king, is the Cavendish banana, a 19th- century British discovery from southern China. The Cavendish is resistant to Panama disease and, as a result, it literally saved the international banana industry. During the 1960s, it replaced the Gros Michel on supermarket shelves. If you buy a banana today, it is almost certainly a Cavendish. But even so, it is a minority in the world’s banana crop.
Banana is widely known and eaten daily. It is the largest producer of calories and over 500 million people depend on this crop. Although bananas might have resisted the Panama disease a greater resistance will be needed to withstand black Sigatoka disease. The Sigatoka disease which is also a fungal disease was first sighted in Fiji 1963. The black Sigatoka generates brown wounds on leaves causing premature ripening. It is also capable of cutting crops yield to over 50 to 70 per cent and also cutting the productivity lifetime of bananas from 30 to as short as 3 years. Planters keep the black Sigatoka in check by frequent chemical use, 40 as a basic number of chemical spraying annually. But diseases like black Sigatoka adapt to these fungicides. Frison says, “ as soon as you bring a new fungicide they develop resistance”. “One thing we can be sure of is that black Sigatoka won’t lose in this battle”. Some planters are unable to afford these fungicides, so, all they can do is watch their plants die. Brazil's leading banana pathologist with the government research EMBRAPA Luadir Gasparotto, says “Most of the banana fields in Amazonia have already being destroyed by the disease. Predicting a fall in production to 70 per cent, with an only option to find a new variety.
With most crops, such a threat would unleash an army of breeders, scouring the world for resistant relatives whose traits they can breed into commercial varieties. Not so with the banana. Because all edible varieties are sterile, bringing in new genetic traits to help cope with pests and diseases is nearly impossible. Nearly, but not totally. Very rarely, a sterile banana will experience a genetic accident that allows an almost normal seed to develop, giving breeders a tiny window for improvement. Breeders at the Honduran Foundation of Agricultural Research have tried to exploit this to create disease-resistant varieties. Further back-crossing with wild bananas yielded a new seedless banana resistant to both Sigatoka and Panama disease.
The results of the new hybrid are rather disheartening as western supermarkets and peasant farmers dislike it. Some say it tastes like an apple instead of a banana, causing planters to grow other plants avoiding banana. And the banana companies also abandoned the breeding effort and invested more assets on finding new fungicides. The Cavendish is still the only success for over 40 years in the breeding program. “It was quite expensive and we got nothing back, ” says Ronald Romero, head of research at Chiquita, one of the three biggest companies dominating the banana industry.
A global consortium of scientists led by Frison announced last year, plans to sequence the banana genome within five years. Being the first edible fruit sequenced. Well, almost edible. The association will be sequencing wild inedible bananas from East Asia because they are resistant to the fast-growing fungus, the black Sigatoka. Then the genes resisting black Sigatoka can be identified and processed in a laboratory tissue culture of cells from edible varieties. This can thereafter turn to new disease-resistant plants and further distributed to local farmers.
It sounds promising, but the big banana companies have, until now, refused to get involved in GM research for fear of alienating their customers. “Biotechnology is extremely expensive and there are serious questions about consumer acceptance,” says David McLaughlin, Chiquita’s senior director for environmental affairs. With scant funding from the companies, the banana genome researchers are focusing on the other end of the spectrum. Even if they can identify the crucial genes, they will be a long way from developing new varieties that smallholders will find suitable and affordable. But whatever biotechnology’s academic interest, it is the only hope for the banana. Without it, banana production worldwide will head into a tailspin. Preventing the extinction of the banana could be both a lifesaver for hungry and impoverished Africans and the most popular product on the world’s supermarket shelves.
Reading Passage Vocabulary
The bananas we know today all originate from Musa acuminata, a wild, spindly banana plant native to the South East Asian islands that make up modern-day Indonesia, Malaysia and Papua New Guinea. The evolution of banana has been traced back to 10,000 years by agricultural experts. It has been at an evolutionary standstill ever since it was first propagated in the jungles of South-East Asia at the end of the last ice age. Normally wild bananas produce tiny fruits filled with hard seeds that make the fruit virtually inedible. But now and then, hunter-gatherers must have discovered rare mutant plants that produced seedless, edible fruits. Genetics now know that most of these edible plants are mostly results of accidental mutation that gave their cells three copies of each chromosome instead of two. This alteration prevents seeds and pollen from developing normally, rendering the mutant plants sterile, which is why scientists believe the world’s famous fruit (banana) could disappear forever in 10 years’ time as it lacks the genetic capability to ward off pests and diseases that are in Central America, Africa and Asia.
The banana needs a pick-me-up fast. But science has so far let it down. For decades plant breeders have all but ignored it, because developing new varieties without the help of sexual reproduction is expensive and time-consuming. As a result, most people in the developed world eat just one variety. In some ways, the banana today resembles the potato before blight brought famine to Ireland a century and a half ago. But it holds a lesson for other crops, too, says Emile Frison of the International Network for the Improvement of Banana and Plantain in Montpellier, France. Frison explains, “The state of banana can teach a broader lesson: the increasing requirements of food crops around the world is threatening their ability to adapt and survive.”
The unproductive hybrids were cultivated by the first men. They were planted by replanting their cuttings from their stem. And descendants of the results of those plantings are the bananas we eat today. Each is a virtual clone, almost devoid of genetic diversity. And that uniformity makes it ripe for disease like no other crop on Earth. Traditional varieties of sexually reproducing crops have always had a much broader genetic base, and the genes will recombine in new arrangements in each generation giving them enough resist the ability to fight pests and diseases. But that advantage is fading fast with the repeated plantation of high yielding varieties by planters. Plant breeders work tirelessly to maintain the resistance of standardized crops because even yields of the most productive crop could just nose dive, so they have to keep everything in check at all times. Even the director of the Rome-based International Plant Genetic Resources Institute, Geoff Hawtin says “When some pest or disease comes along, severe epidemics can occur.”
Banana is an interesting case study. Until the 1950s, one variety, the Gros Michel, dominated the world’s commercial banana business. Found by French botanists in Asia in the 1820s, the Gros Michel was by all accounts a fine banana, richer and sweeter than today’s standard banana without the latter’s bitter aftertaste when green. But it was vulnerable to a soil fungus that produced a wilt known as Panama disease. “Once the fungus gets into the soil, it remains there for many years. There is nothing farmers can do. Even chemical spraying won’t get rid of it,” says Rodomiro Ortiz, director of the International Institute for Tropical Agriculture in Ibadan, Nigeria. So, plantation owners played a running game, abandoning infested fields and moving to “clean” land - until they ran out of clean land in the 1950s and had to abandon the Gros Michel. Its successor, and still the reigning commercial king, is the Cavendish banana, a 19th- century British discovery from southern China. The Cavendish is resistant to Panama disease and, as a result, it literally saved the international banana industry. During the 1960s, it replaced the Gros Michel on supermarket shelves. If you buy a banana today, it is almost certainly a Cavendish. But even so, it is a minority in the world’s banana crop.
Banana is widely known and eaten daily. It is the largest producer of calories and over 500 million people depend on this crop. Although bananas might have resisted the Panama disease a greater resistance will be needed to withstand black Sigatoka disease. The Sigatoka disease which is also a fungal disease was first sighted in Fiji 1963. The black Sigatoka generates brown wounds on leaves causing premature ripening. It is also capable of cutting crops yield to over 50 to 70 per cent and also cutting the productivity lifetime of bananas from 30 to as short as 3 years. Planters keep the black Sigatoka in check by frequent chemical use, 40 as a basic number of chemical spraying annually. But diseases like black Sigatoka adapt to these fungicides. Frison says, “ as soon as you bring a new fungicide they develop resistance”. “One thing we can be sure of is that black Sigatoka won’t lose in this battle”. Some planters are unable to afford these fungicides, so, all they can do is watch their plants die. Brazil's leading banana pathologist with the government research EMBRAPA Luadir Gasparotto, says “Most of the banana fields in Amazonia have already being destroyed by the disease. Predicting a fall in production to 70 per cent, with an only option to find a new variety.
With most crops, such a threat would unleash an army of breeders, scouring the world for resistant relatives whose traits they can breed into commercial varieties. Not so with the banana. Because all edible varieties are sterile, bringing in new genetic traits to help cope with pests and diseases is nearly impossible. Nearly, but not totally. Very rarely, a sterile banana will experience a genetic accident that allows an almost normal seed to develop, giving breeders a tiny window for improvement. Breeders at the Honduran Foundation of Agricultural Research have tried to exploit this to create disease-resistant varieties. Further back-crossing with wild bananas yielded a new seedless banana resistant to both Sigatoka and Panama disease.
The results of the new hybrid are rather disheartening as western supermarkets and peasant farmers dislike it. Some say it tastes like an apple instead of a banana, causing planters to grow other plants avoiding banana. And the banana companies also abandoned the breeding effort and invested more assets on finding new fungicides. The Cavendish is still the only success for over 40 years in the breeding program. “It was quite expensive and we got nothing back, ” says Ronald Romero, head of research at Chiquita, one of the three biggest companies dominating the banana industry.
A global consortium of scientists led by Frison announced last year, plans to sequence the banana genome within five years. Being the first edible fruit sequenced. Well, almost edible. The association will be sequencing wild inedible bananas from East Asia because they are resistant to the fast-growing fungus, the black Sigatoka. Then the genes resisting black Sigatoka can be identified and processed in a laboratory tissue culture of cells from edible varieties. This can thereafter turn to new disease-resistant plants and further distributed to local farmers.
It sounds promising, but the big banana companies have, until now, refused to get involved in GM research for fear of alienating their customers. “Biotechnology is extremely expensive and there are serious questions about consumer acceptance,” says David McLaughlin, Chiquita’s senior director for environmental affairs. With scant funding from the companies, the banana genome researchers are focusing on the other end of the spectrum. Even if they can identify the crucial genes, they will be a long way from developing new varieties that smallholders will find suitable and affordable. But whatever biotechnology’s academic interest, it is the only hope for the banana. Without it, banana production worldwide will head into a tailspin. Preventing the extinction of the banana could be both a lifesaver for hungry and impoverished Africans and the most popular product on the world’s supermarket shelves.