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READING PASSAGE 2
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You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 on
pages 5 and 6
The Constant Evolution of the Humble Tomato
Heirloom tomatoes—varieties that have been passed down through several generations of a family
because they are thought to have a particularly good flavor—are really no more 'natural' than the
varieties available in grocery stores. New studies promise to restore their lost, healthy genes.
A
Famous for their taste, color, and organic appearance, heirloom tomatoes are favorites of gardeners
and advocates of locally grown foods. The tomato enthusiast might conclude that, given the
immense varieties, heirlooms must have a more diverse and superior set of genes than the tomatoes
available in grocery stores, those ordinary hybrid varieties such as cherry and plum. However, their
seeming diversity is only skin-deep: heirlooms are actually feeble and inbred—the defective product
of breeding experiments that began hundreds of years ago, and exploded thanks to enthusiastic
backyard gardeners. The irony of all this," says Steven Tanksley, a geneticist at Cornell University, is
all that diversity of heirlooms can be accounted for by a handful of genes. There're probably no more
than 10 mutant genes that create the diversity of heirlooms you see. But rather than simply proving
that the myth about the heirloom's diversity is wrong, Tanksley's deconstruction of the tomato
genome, along with work by others, is showing how a small berry-like fruit from the Andes became
one of the world's top crops.
B
The cultivated tomato is a member of the nightshade family that includes New World crops such as
the potato, which spread around the globe after Christopher Columbus brought them back to Spain
in the 15th century. But whereas scientists have uncovered a wealth of archaeological evidence on
early farming practices in the New World, the record is blank when it comes to the tomato. The
modern tomato seems to have its origins in the Andes in South America and may have been
domesticated in Vera Cruz, Mexico. Primitive varieties still grow throughout the Americas. All told,
botanists call as many as 13 species 'tomatoes' and consider an additional four to be closely related.
C
One might assume that one of these known wild species became today's cultivated crop, but that's
not the case: the Mother Tomato has never been found. The closest relative is the currant tomato,
which, based on genetic comparisons, split from today's tomato some 1.4 million years ago. So
researchers like Tanksley have to work backward, crossing tomato varieties and species in order to
understand how various genes influence shape and size. Once isolated, Tanksley later inserts those
genes into other tomato varieties to make his case with a dramatic transformation.
D
Tanksley concludes from his analyses that in their effort to make bigger, tastier, and faster-growing
fruit, our ancestors ultimately exploited just 30 mutations out of the tomato's 35,000 genes. Most of
these genes have only small effects on tomato size and shape, but recently Tanksley and his
colleagues reported that they found a gene that increases fruit size by 50 percent. It was probably
the most important event in domestication. The first written record of tomatoes—from Spain in the
1500s—confirms that this mutation, which enlarges tomatoes by producing compartments known as
locules, existed back in the same yellow tomatoes that gave Italians the word pomodoro, or golden
apple. Besides size, tomato farmers also selected for shape. To discover those genes, Esther van der
Knaap, a Tanksley alumnus now at The Ohio State University, took a gene from one heirloom tomato
and inserted it into a wild relative. She observed that, as a result, the tiny fruits became shaped like
pears.
E
The selection of these traits has, however, affected the heirloom's hardiness. They often suffer from
infections that cause the fruit to crack, split, and otherwise rot quickly. Wild plants must
continuously evolve to fend off such infections, points out Roger Chetelat of the Tomato Genetics
Resource Center at the University of California. But in their quest for size, shape, and flavor, humans
have inadvertently eliminated defensive genes. As a result, most possess only a single diseaseresistant
gene. Chetelat elaborates that heirlooms' taste may have less to do with their genes than
with the productivity of the plant and the growing environment. Any plant that produces only two
fruits, as heirlooms sometimes do, is highly likely to produce juicier, sweeter, and more flavorful fruit
than varieties that produce 100, as commercial types do. In addition, heirlooms are sold ripened on
the vine, a certain way to get tastier results than allowing them to mature on the shelf. This means
breeders feel confident that getting germ-beating genes back into heirlooms won't harm the
desirable aspects of the fruit. Modern breeding has resuscitated grocery store tomatoes with an
influx of wild genes; in the past 50 years, as many as 40 disease-resistant genes have been bred back
into commercial crops.
F
In 1996, a tomato breeder and former Tanksley student named Doug Heath began a favorite project.
After 12 years of traditional breeding with the help of molecular markers, he created a new multicolored
tomato less prone to cracking and also endowed with 12 disease-resistant genes. The
original heirloom plant, Heath explains, had defective flowers, which is one reason why it produced
only two fruits compared with the 30 he gets from his new variety. He claims he is also able to
maintain a comparable flavor and sugar profile even on productive plants. The heirloom's defects
are, after all, just an accident of a narrow breeding strategy left over from the very beginning of
genetic modification.
Questions 14-17
Reading Passage 2 has six paragraphs, A-F.
Which paragraph contains the following information?
Write the correct letter, A-F, in boxes 14-17 on your answer sheet
14. An explanation of research aimed at restoring the health of the heirloom tomato
15. A reference to a false belief about the heirloom tomato
16. A description of the flavor of the heirloom tomato
17. A reference to a single gene that significantly improves the cultivation of tomatoes
Questions 18-21
Look at the following statements (Questions 18-21) and the list of researchers below. Match each
statement with the correct researcher, A, B, C, or D.
Write the correct letter, A, B, C, or D, in boxes 18-21 on your answer sheet.
18. The transplanting of certain genes into tomatoes can change their shape.
19. The flavor of the heirloom tomato is largely dependent on actual yield and cultivation.
20. A new type of tomato can be produced that is stronger than the original heirloom tomato yet
equally sweet and flavorsome.
21. The wide variety of heirloom tomatoes is due to only a small number of genes.
List of Researchers
A. Steven Tanksley
B. Esther van der Knaap
C. Roger Chetelat
D. Doug Heath
Questions 22-26
Complete the sentences below.
Choose ONE WORD ONLY from the passage for each answer.
Write your answers in boxes 22-26 on your answer sheet.
22. There is little information on the origin of the tomato despite the existence of data on the
growing of other New World crops.
23. Although it is uncertain, the tomato is thought to have first grown in the __________.
24. In regard to genetic similarities, the type of tomato __________ is the nearest to the earliest.
25. A genetic __________ which is evident in pomodoro produced larger tomatoes.
26. __________ are a problem for heirloom tomatoes because they frequently lead to damage and
deterioration.
ANSWERS:
🔷 Questions 14–17
14. An explanation of research aimed at restoring the health of the heirloom tomato
✅ F — “After 12 years of traditional breeding with the help of molecular markers, he created a new multi-colored tomato less prone to cracking and also endowed with 12 disease-resistant genes.”
15. A reference to a false belief about the heirloom tomato
✅ A — “The tomato enthusiast might conclude… heirlooms must have a more diverse and superior set of genes… However, their seeming diversity is only skin-deep: heirlooms are actually feeble and inbred…”
16. A description of the flavor of the heirloom tomato
✅ E — “…heirlooms' taste may have less to do with their genes than with the productivity of the plant and the growing environment… highly likely to produce juicier, sweeter, and more flavorful fruit…”
17. A reference to a single gene that significantly improves the cultivation of tomatoes
✅ D — “…found a gene that increases fruit size by 50 percent. It was probably the most important event in domestication.”
🔷 Questions 18–21
18. The transplanting of certain genes into tomatoes can change their shape.
✅ B. Esther van der Knaap — “…took a gene from one heirloom tomato and inserted it into a wild relative… fruits became shaped like pears.”
19. The flavor of the heirloom tomato is largely dependent on actual yield and cultivation.
✅ C. Roger Chetelat — “…heirlooms' taste may have less to do with their genes than with the productivity of the plant and the growing environment.”
20. A new type of tomato can be produced that is stronger than the original heirloom tomato yet equally sweet and flavorsome.
✅ D. Doug Heath — “…created a new multi-colored tomato less prone to cracking… able to maintain a comparable flavor and sugar profile…”
21. The wide variety of heirloom tomatoes is due to only a small number of genes.
✅ A. Steven Tanksley — “…all that diversity of heirlooms can be accounted for by a handful of genes.”
🔷 Questions 22–26
22. There is little information on the origin of the tomato despite the existence of data on the growing of other New World crops.
✅ archaeological
23. Although it is uncertain, the tomato is thought to have first grown in the __________.
✅ Andes
24. In regard to genetic similarities, the type of tomato __________ is the nearest to the earliest.
✅ currant
25. A genetic __________ which is evident in pomodoro produced larger tomatoes.
✅ mutation
26. __________ are a problem for heirloom tomatoes because they frequently lead to damage and deterioration.
✅ infections
Final answers:
✅ 14 — F
✅ 15 — A
✅ 16 — E
✅ 17 — D
✅ 18 — B
✅ 19 — C
✅ 20 — D
✅ 21 — A
✅ 22 — archaeological
✅ 23 — Andes
✅ 24 — currant
✅ 25 — mutation
✅ 26 — infections
PASSWORD
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