http://www.commondreams.org/views03/0719-02.htm
Published on Saturday,
July 19, 2003 by the Globe and Mail / Canada
Yes, We'll
Have No Bananas - Thanks to Selective Breeding, our Favourite
Fruit can Neither Reproduce nor Defend Itself from Disease
by Robert Alison
The banana is about to disappear from store shelves around the
globe.
Experts say the world's favourite fruit will pass into oblivion
within
a decade. No more fresh bananas. No more banana bread. No more
banana
muffins or banana cream pie.
Why? Because the banana
is the victim of centuries of genetic tampering.
Scientists say they will be unable to prevent the extirpation
of the
banana as an edible commercial crop. And its demise may be one
more
powerful argument in the hands of those who are concerned about
genetic
modification of foods.
The banana's main problem
is that it has become sterile and seedless
as a result of 10,000 years of selective breeding. It has, over
time,
become a plant with unvarying genetic sameness. The genetic diversity
needed to cope with environmental stresses, such as diseases and
crop
pests, has long ago been bred out of the banana. Consequently,
the
banana plantations of the world are completely vulnerable to
devastating environmental pressures.
According to Emile
Frison, newly appointed director-general
of the Rome-based International Plant Genetic Resources Institute,
science is helpless to prevent the demise of the banana. Already,
he says, as much as 50 per cent of the world's banana harvest
is lost to insects and disease.
When humankind first
encountered this fruit thousands of years
ago we were probably not impressed by the almost inedible giant
wild bananas. Historic mutations, rare and accidental, produced
seedless bananas through chromosome triplication. Ancient humans
focused on these seedless, pollen-less mutants to generate
progressively more edible crops. Eventually, edible banana
flesh retained only a few vague traces of the viable seeds
once carried in the ancestral wild stock.
Ancient plant breeders
grew edible bananas by grafting sterile
mutants onto wild stems. This process was repeated for thousands
of years to produce the emasculated, sterile -- and defenceless
-- plantation banana that currently feeds millions of people
globally.
But the stage was set
for the final act in the story of this
beloved yellow fruit in the 1950s. By then, generations of
selective breeding had long since inhibited natural banana
reproduction, and genetic tinkering had all but obliterated
most commercial varieties. Eventually, one morph remained,
the Gros Michel variety. All domestic stock was its clone,
an exact genetic copy of that one variety. Every tree was
equally vulnerable to plant disease, crop pests and climate
variables.
Then Panama disease,
a soil fungus, attacked banana plantations
and the genetically enfeebled Gros Michel banana was virtually
wiped out. By 1960, the Gros Michel was no longer a viable crop.
Tireless agricultural research eventually produced a successor,
the Cavendish. For the past 40 years or so, the Cavendish has
been virtually the only commercially grown stock available on
store shelves in developed nations.
In the tropics, you
can still find other, less desirable banana
varieties, mainly grown as a starchy food staple rather than a
sweet treat. But these tropical bananas aren't much like their
commercial cousins in North American supermarkets. They taste
bland. Their texture is often fibrous and mealy. North American
consumers would probably find them quite unpalatable compared
to
the Cavendish, which is sweeter and smoother-textured.
But like its genetic
predecessor, the Cavendish is also sterile,
equally unprotected from diseases and crop pests. And now a powerful
plant pathogen, the Black Sigatoka fungus, has appeared on the
scene,
attacking the Cavendish stock around the world. Banana yields
have
already dropped by 50-70 per cent, and banana-tree life spans
have
been reduced from about 30 years to just about two years. The
genetic uniformity among Cavendish bananas has made them helpless
to fight Black Sigatoka.
Nor can chemical spraying
save the day. Commercial growers have
long attempted to control the fungus using fungicides such as
dibromochloropropane (now banned because it caused sterility
and leukemia among banana industry workers). According to
Dr. Frison, even powerful fungicides don't work against
Black Sigatoka because the fungus is rapidly capable of
developing resistance to them. Indeed, banana plantations
in Costa Rica and the Amazon have already been largely
destroyed.
The selective plant
breeding that has brought us to this
impasse is comparable to genetic engineering. Both change
the genetic makeup of a plant, perhaps irreversibly. So the
case of the banana gives ammunition to critics of genetic
engineering and to their claim that much can go wrong when
we tamper with plant genetics.
Such warnings aren't
new. In 1995, biologists warned that
changing the genetic makeup of a plant is like playing with
fire. Even so, genetic alteration continues. At Oregon State
University, scientists are at work on generating sterility in
poplar trees; the Canadian Forest Service is looking into
breeding insect resistance in white spruces; at the University
of California, work is being done on changing root systems
in walnut trees. And at the Independent University in Madrid,
orange trees are being modified to promote early fruit-bearing
and to grow oranges that are easier to peel.
The International Plant
Genetic Resources Institute's
Dr. Frison says biotechnology could still delay the loss
of the banana, by providing the genetic blueprint of inedible
wild varieties that can be genetically altered to create a
genetically modified product. Does this hold out hope of an
11th-hour reprieve? Will consumers accept a GM substitute
for the sweet fruit they enjoy so much?
The
disappearance of the banana should be a wakeup call
-- to what can result from reckless genetic manipulation,
complacency and inattention. If this can happen to the
world's most popular fruit with all humanity as its witness,
imagine what could happen to more obscure, but no less
useful plants whose fates are less publicized and open
to public scrutiny.
Robert Alison, a consultant
biologist based in Orillia, Ont.,
is a former senior biologist for the Ontario Ministry of
Natural Resources.
© 2003 Bell Globemedia
Interactive Inc
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