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SECTION 1
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Going
Bananas
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A
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The
world's favourite fruit could disappear forever in 10 years’ time. The
banana is among the world’s oldest crops.
Agricultural scientists believe that the first edible banana was discovered around ten thousand
years ago. 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 the wild banana, a
giant jungle herb called Musa acuminata, contains a
mass of hard seeds that make the fruit virtually inedible. But now and
then, hunter-gatherers must have discovered rare
mutant plants that produced seed-less, edible fruits. Geneticists now know that the vast
majority of these soft-fruited plants resulted from genetic
accidents that gave their cells three copies of each chromosome instead of
the usual two. This imbalance prevents seeds
and pollen from developing normally, rendering the
mutant plants sterile. And that is why some scientists believe the world's
most popular fruit could
be doomed. It lacks the genetic diversity to fight off pests and diseases
that are invading the banana plantations of
Central America and the small-holdings of Africa and Asia alike.
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B
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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, top banana at the
International Network for the Improvement of Banana and Plantain in Montpellier, France.
"The state of the banana’, Frison warns, "can teach a broader lesson the increasing
standardisation of food crops round the world is threatening their ability to adapt and
survive."
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C
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The
first Stone Age plant breeders cultivated these sterile freaks by
replanting cuttings from
their stems. And the descendants of those original cuttings are the bananas
we still 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. This gives them much greater flexibility
in evolving responses to disease - and far more genetic resources to draw
on in the face of an attack. But that advantage is fading fast, as growers
increasingly plant the same few, high-yielding varieties. Plant breeders
work feverishly to maintain resistance in these standardized crops. Should
these efforts falter, yields of even the most productive crop could swiftly
crash. "When some pest or disease comes along, severe epidemics can
occur,’says Geoff Hawtin, director of the Rome-based International Plant
Genetic Resources Institute.
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D
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The banana is
an excellent case in point. Until the 1950s，
one variety, the Gros Michel, dominated
the world’s commercial banana business. Found by French botanists in Asian the 1820s，
the Gros Michel was by all accounts a fine banana, richer and sweeter than today's standard banana and 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 so "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.
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E
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Half
a billion people in Asia and Africa depend on bananas. Bananas provide the
largest source of calories and are eaten
daily. Its name is synonymous with food. But the day of reckoning may be coming for the
Cavendish and its indigenous kin. Another fungal disease,
black Sigatoka, has become a global epidemic since its first appearance in
Fiji in 1963. Left to itself, black
Sigatoka which causes brown wounds on leaves and pre- mature fruit ripening - cuts
fruit yields by 50 to 70 per cent and reduces the productive lifetime of
banana plants from 30 years to as little as 2 or 3. Commercial growers keep
Sigatoka at bay by a massive chemical assault. Forty sprayings of fungicide
a year is typical. But despite the fungicides, diseases such as black
Sigatoka are getting more and more difficult to control. "As soon as
you bring in a new fungicide, they develop resistance”, says Frison.”One
thing we can be sure of is that the Sigatoka won’t lose in this
battle." Poor farmers, who cannot afford chemicals, have it even
worse. They can do little more than watch their plants die. "Most of
the banana fields in Amazonia have already been destroyed by the
disease," says Luadir Gasparotto, Brazil’s leading banana pathologist
with the government research agency EMBRAPA. Production is likely to fall by
70 percent as the disease spreads, he predicts. The only option will be to
find a new variety.
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F
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But how?
Almost all edible varieties are susceptible to the diseases, so growers
cannot simply change to a different banana.
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 backcrossing with wild bananas
yielded a new seedless banana resistant to both
black Sigatoka and Panama disease.
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G
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Neither
Western supermarket consumers nor peasant growers like the new hybrid. Some accuse it of tasting more like
an apple than a banana. Not surprisingly, the majority of plant breeders have till now
turned their backs on the banana and got to work on easier plants. And commercial banana
companies are now washing their hands of the whole breeding
effort, preferring to fund a search for new fungicides instead. "We
supported a breeding programme
for 40 years, but it wasn’t able to develop an alternative to Cavendish. It was very expensive and
we got nothing back," says Ronald Romero, head of research at Chiquita, one of the Big Three
companies that dominate the international banana trade.
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H
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Last year, a
global consortium of scientists led by Frison announced plans to sequence the banana genome within five years.
It would be the first edible fruit to be sequenced. Well,
almost edible. The group will actually be sequencing inedible wild bananas
from East Asia because many of these are
resistant to black Sigatoka. If they can pinpoint the genes that help these wild varieties
to resist black Sigatoka, the protective genes could be introduced into laboratory tissue
cultures of cells from edible varieties. These could then be propagated into new,
resistant plants and passed on to farmers.
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I
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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,11 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 banana production worldwide will head into a
tailspin. We may even see the extinction of the banana
as both a lifesaver for hungry and impoverished Africans and as the most
popular product on the world's supermarket
shelves.
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Questions 1-3
Complete the
sentences below with NO MORE THAN THREE WORDS from the passage.
In boxes 1-3 on
your answer sheet, write
Write your answers
in boxes 1-3 on your answer sheet
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1
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Banana was first eaten as a fruit by
humans _____________ years ago.
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2
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Banana was first planted in _____________
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3
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Wild banana’s taste is adversely affected by its _____________
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Questions 4-10
Look at the
following statements (Questions 4-10) and the list of people below Match each
statement with the correct person, A-I.
Write the correct
letter: A-I, in boxes 4-10 On your answer sheet.
NB You may use any
letter more than once.
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4
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Pest invasion may seriously damage banana
industry.
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5
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The effect of fungal infection in soil is
often long-lasting.
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6
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A commercial manufacturer gave up on breeding bananas for disease
resistant
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7
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Banana disease may develop resistance to
chemical sprays.
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8
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A banana disease has destroyed a large number of banana plantations.
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9
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Consumers would not accept genetically
altered crop.
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10
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Lessons can be learned from bananas for other crops.
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List of People
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A
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Rodomiro
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B
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David
Maclaughlin
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C
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Emile
Frison
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D
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Ronald
Romero
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E
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Luadir
Gasparotto
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F
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Geoff
Hawtin
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Questions 11-13
Do the following
statements agree with the information given in Reading Passage 1?
In boxes 11-13 on
your answer sheet, write
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TRUE
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if
the statement is true
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FALSE
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if
the statement is false
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NOT
GIVEN
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if the
information is not given in the passage
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11
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Banana is the oldest known fruit
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12
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Gros Michel is still being used as a
commercial product
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13
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Banana is a main food in some countries
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