雅思阅读第032套P1-Going Bananas
READING PASSAGE 1
You should spend about 20minutes on Questions 1-13, which are based on Reading Passage 1below.
Going Bananas
The world's favourite fruitcould disappear forever in 10 years’ time
The banana is among the world'soldest crops. Agricultural scientists believe that the first edible banana wasdiscovered around ten thousand years ago. It has been at an evolutionarystandstill ever since it was first propagated in the jungles of South-East Asiaat the end of the last ice age. Normally the wild banana, a giant jungle herbcalled Musa acuminata, contains a mass of hard seeds that make the fruitvirtually inedible. But now and then, hunter- gatherers must have discoveredrare mutant plants that produced seedless, edible fruits. Geneticists now knowthat the vast majority of these soft-fruited I plants resulted from geneticaccidents that gave their cells three copies of each chromosome instead of theusual two. This imbalance prevents seeds and pollen from developing normally,rendering the mutant plants sterile. And that is why some scientists believethe world’s most popular fruit could be doomed. It lacks the genetic diversityto fight off pests and diseases that are invading the banana plantations ofCentral America and the smallholdings of Africa and Asia alike.
In some ways, the banana todayresembles the potato before blight brought famine to Ireland a century and ahalf ago. But “it holds a lesson for other crops, too,” says Emile Frison, topbanana at the International Network for the Improvement of Banana and Plantainin Montpellier, France. “The state of the banana,” Frison warns, “can teach abroader lesson: the increasing standardisation of food crops round the world isthreatening their ability to adapt and survive.”
The first Stone Age plantbreeders cultivated these sterile freaks by replanting cuttings from theirstems. And the descendants of those original cuttings are the bananas we stilleat today. Each is a virtual clone, almost devoid of genetic diversity. Andthat uniformity makes it ripe for disease like no other crop on Earth.Traditional varieties of sexually reproducing crops have always had a muchbroader genetic base, and the genes will recombine in new arrangements in eachgeneration. This gives them much greater flexibility in evolving responses todisease - 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 resistancein these standardised crops. Should these efforts falter, yields of even themost productive crop could swiftly crash. “When some pest or disease comesalong, severe epidemics can occur,” says Geoff Hawtin, director of theRome-based International Plant Genetic Resources Institute.
The banana is an excellent casein point. Until the 1950s, one variety, the Gros Michel, dominated the world’scommercial banana business. Found by French botanists in Asia in the 1820s, theGros Michel was by all accounts a fine banana, richer and sweeter than today’sstandard banana and without the latter’s bitter aftertaste when green. But itwas 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 isnothing farmers can do. Even chemical spraying won’t get rid of it,” saysRodomiro Ortiz, director of the International Institute for TropicalAgriculture in Ibadan, Nigeria. So plantation owners played a running game,abandoning infested fields and moving to “clean” land - until they ran out ofclean land in the 1950s and had to abandon the Gros Michel. Its successor, andstill the reigning commercial king, is the Cavendish banana, a 19th-centuryBritish discovery from southern China. The Cavendish is resistant to Panamadisease and, as a result, it literally saved the international banana industry.During the 1960s, it replaced the Gros Michel on supermarket shelves. If youbuy a banana today, it is almost certainly a Cavendish. But even so, it is aminority in the world’s banana crop.
Half a billion people in Asiaand Africa depend on bananas. Bananas provide the largest source of caloriesand are eaten daily. Its name is synonymous with food. But the day of reckoningmay be coming for the Cavendish and its indigenous kin. Another fungaldisease, black Sigatoka, has become a global epidemic since its firstappearance in Fiji in 1963. Left to itself, black Sigatoka - which causes brownwounds on leaves and premature fruit ripening - cuts fruit yields by 50 to 70per cent and reduces the productive lifetime of banana plants from 30 years toas little as 2 or 3. Commercial growers keep black Sigatoka at bay by a massivechemical assault. Forty sprayings of fungicide a year is typical. But despitethe fungicides, diseases such as black Sigatoka are getting more and moredifficult to control. “As soon as you bring in a new fungicide, they developresistance,” says Frison. “One thing we can be sure of is that black Sigatokawon't lose in this battle.” Poor farmers, who cannot afford chemicals, have iteven worse. They cap do little more than watch their plants die. “Most of thebanana fields in Amazonia have already been destroyed by the disease,” says LuadirGasparotto, Brazil’s leading banana pathologist with the government researchagency EMBRAPA. Production is likely to fall by 70 per cent as the diseasespreads, he predicts. The only option will be to find a new variety.
But how? Almost all edible varietiesare susceptible to the diseases, so growers cannot simply change to a differentbanana. With most crops, such a threat would unleash an army of breeders,scouring the world for resistant relatives whose traits they can breed intocommercial varieties. Not so with the banana. Because all edible varieties aresterile, bringing in new genetic traits to help cope with pests and diseases isnearly impossible. Nearly, but not totally. Very rarely, a sterile banana willexperience a genetic accident that allows an almost normal seed to develop,giving breeders a tiny window for improvement. Breeders at the HonduranFoundation of Agricultural Research have tried to exploit this to createdisease-resistant varieties. Further back-crossing with wild bananas yielded anew seedless banana resistant to both black Sigatoka and Panama disease.
Neither Western supermarketconsumers nor peasant growers like the new hybrid. Some accuse it of tastingmore like an apple than a banana. Not surprisingly, the majority of plantbreeders have till now turned their backs on the banana and got to work oneasier plants. And commercial banana companies are now washing their hands ofthe whole breeding effort, preferring to fund a search for new fungicidesinstead. “We supported a breeding programme for 40 years, but it wasn't able todevelop an alternative to the Cavendish. It was very expensive and we gotnothing back,” says Ronald Romero, head of research at Chiquita, one of the BigThree companies that dominate the international banana trade.
Last year, a global consortiumof scientists led by Frison announced plans to sequence the banana genomewithin five years. It would be the first edible fruit to be sequenced. Well,almost edible. The group will actually be sequencing inedible wild bananasfrom East Asia because many of these are resistant to black Sigatoka. If theycan pinpoint the genes that help these wild varieties to resist black Sigatoka,the protective genes could be introduced into laboratory tissue cultures of cellsfrom edible varieties. These could then be propagated into newdisease-resistant plants and passed on to farmers.
It sounds promising, but thebig banana companies have, until now, refused to get involved in GM researchfor fear of alienating their customers. “Biotechnology is extremely expensiveand there are serious questions about consumer acceptance,” says DavidMcLaughlin, Chiquita’s senior director for environ- mental affairs. With scantfunding from the companies, the banana genome researchers are focusing on theother end of the spectrum. Even if they can identify the crucial genes, theywill be a long way from developing new varieties that smallholders will findsuitable and affordable. But whatever biotechnology’s academic interest, it isthe only hope for the banana. Without it, banana production worldwide willhead into a tailspin. We may even see the extinction of the banana as both alifesaver for hungry and impoverished Africans and the most popular product onthe world’s supermarket shelves.
SECTION 1: QUESTIONS 1-13
Questions 1-3
Complete the sentences belowwith NO MORE THAN THREE WORDS from the passage for eachanswer.
Write your answers inboxes 1-3 on your answer sheet.
Banana was first eaten as afruit by humans almost 1 _________________ yearsago.
Banana was first plantedin 2 _________________
Wild banana’s taste isadversely affected by its 3 _________________
Questions 4-10
Look at the statements(Questions 4-10) and the list of people. Match each statement withthe correct person A-F.
Write the correct letter A-F inboxes 4-10 on your answer sheet.
NB You may use anyletter more than once.
List of People
A
Rodomiro Ortiz
B
David McLaughlin
C
Emile Frison
D
Ronald Romero
E
Luadir Gasparotto
F
Geoff Hawtin
4 ____________ Apest invasion may seriously damage banana industry.
5 ____________ The effect of fungal infection in soil is often long-lasting.
6 ____________ A commercial manufacturer gave up on breeding bananas fordisease-resistant
7 ____________ Banana disease may develop resistance to chemical sprays.
8 ____________ A banana disease has destroyed a large number of banana plantations.
9 ____________ Consumers would not accept genetically altered crops.
10 ____________ Lessonscan be learned from bananas for other crops.
Questions 11-13
Do the following statementsagree with the information given in Reading Passage 1?
In boxes 11-13 onyour answer sheet write
TRUE
if the statement agrees with the information
FALSE
if the statement contradicts the information
NOT GIVEN
If there is no information on this
11 _________________ Banana is the oldest known fruit.
12 _________________ Gros Michel is still being used as a commercial product.
13 _________________ Banana is the main food in some countries.
答案
雅思阅读第032套P1-Going Bananashttp://www.tuonindefu.com/?p=2282雅思阅读第032套P1:Going Bananas
