Cambridge IELTS Academic 17
TEST 39
Questions 14 – 17
Reading Passage 2 has seven paragraphs, A-G.
Which section contains the following information?
Write the correct letter,
A-G
, in boxes
14-17
on your answer sheet.
NB
You may use any letter more than once.
14
a mention of negative attitudes towards stadium building projects
15
figures demonstrating the environmental benefits of a certain stadium
16
examples of the wide range of facilities available at some new stadiums
17
reference to the disadvantages of the stadiums built during a certain era
85
TEST 40 READING PASSAGE 2
You should spend about 20 minutes on
Questions 14-18
which are based on
Reading Passage 2 below.
A second attempt at domesticating the tomato
* mutations: changes in an organism’s genetic structure that can be passed down to later generations
A
It took at least 3,000 years for humans
to learn how to domesticate the wild
tomato and cultivate it for food. Now
two separate teams in Brazil and
China have done it all over again in
less than three years. And they have
done it better in some ways, as the
re-domesticated tomatoes are more
nutritious than the ones we eat at
present.
This approach relies on the
revolutionary CRISPR genome
editing technique, in which changes
are deliberately made to the DNA of
a living cell, allowing genetic material
to be added, removed or altered. The
technique could not only improve
existing crops, but could also be used
to turn thousands of wild plants into
useful and appealing foods. In fact,
a third team in the US has already
begun to do this with a relative of the
tomato called the groundcherry.
This fast-track domestication could
help make the world’s food supply
healthier and far more resistant to
diseases, such as the rust fungus
devastating wheat crops.
‘This could transform what we eat,’
says Jorg Kudla at the University of
Munster in Germany, a member of
the Brazilian team. ‘There are 50,000
edible plants in the world, but 90
percent of our energy comes from just
15 crops.’
‘We can now mimic the known
domestication course of major crops
like rice, maize, sorghum or others,’
says Caixia Gao of the Chinese
Academy of Sciences in Beijing. ‘Then
we might try to domesticate plants that
have never been domesticated.’
B
Wild tomatoes, which are native to
the Andes region in South America,
produce pea-sized fruits. Over many
generations, peoples such as the
Aztecs and Incas transformed the plant
by selecting and breeding plants with
mutations* in their genetic structure,
which resulted in desirable traits such
as larger fruit.
But every time a single plant with
a mutation is taken from a larger
population for breeding, much genetic
diversity is lost. And sometimes the
desirable mutations come with less
desirable traits. For instance, the
tomato strains grown for supermarkets
have lost much of their flavour.
By comparing the genomes of modern
plants to those of their wild relatives,
biologists have been working out
what genetic changes occurred
as plants were domesticated. The
teams in Brazil and China have now
used this knowledge to reintroduce
these changes from scratch while
maintaining or even enhancing the
desirable traits of wild strains.
86
C
Kudla’s team made six changes
altogether. For instance, they tripled
the size of fruit by editing a gene
called FRUIT WEIGHT, and increased
the number of tomatoes per truss by
editing another called MULTIFLORA.
While the historical domestication of
tomatoes reduced levels of the red
pigment lycopene – thought to have
potential health benefits – the team
in Brazil managed to boost it instead.
The wild tomato has twice as much
lycopene as cultivated ones; the newly
domesticated one has five times as
much.
‘They are quite tasty,’ says Kudla. ‘A
little bit strong. And very aromatic.’
The team in China re-domesticated
several strains of wild tomatoes with
desirable traits lost in domesticated
tomatoes. In this way they managed to
create a strain resistant to a common
disease called bacterial spot race,
which can devastate yields. They also
created another strain that is more
salt tolerant – and has higher levels
of vitamin C.
D
Meanwhile, Joyce Van Eck at the Boyce
Thompson Institute in New York state
decided to use the same approach
to domesticate the groundcherry or
goldenberry (Physalis pruinosa) for
the first time. This fruit looks similar to
the closely related Cape gooseberry
(Physalis peruviana).
Groundcherries are already sold to a
limited extent in the US but they are
hard to produce because the plant
has a sprawling growth habit and the
small fruits fall off the branches when
ripe. Van Eck’s team has edited the
plants to increase fruit size, make
their growth more compact and to
stop fruits dropping. ‘There’s potential
for this to be a commercial crop,’ says
Van Eck. But she adds that taking
the work further would be expensive
because of the need to pay for a
licence for the CRISPR technology
and get regulatory approval.
E
This approach could boost the use of
many obscure plants, says Jonathan
Jones of the Sainsbury Lab in the
UK. But it will be hard for new foods
to grow so popular with farmers and
consumers that they become new
staple crops, he thinks.
The three teams already have their
eye on other plants that could be
‘catapulted into the mainstream’,
including foxtail, oat-grass and
cowpea. By choosing wild plants that
are drought or heat tolerant, says Gao,
we could create crops that will thrive
even as the planet warms.
But Kudla didn’t want to reveal which
species were in his team’s sights,
because CRISPR has made the
process so easy. ‘Any one with the
right skills could go to their lab and do
this.’
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