Rice And Genetic Engineering
Rice is the main food for about one-third to one-half of the world's
population.
A mature rice plant is usually two to six feet tall. In the
beginning, one shoot
appears. It is followed by one, two, or more offshoots
developing. There are at
least five or six hollow joints for each stalk, and
a leaf for each joint. The
leaf of the rice plant is long, pointed, flat, and
stiff. The highest join of
the rice plant is called the panicle. The rice
grains develop from the panicles.
(Jodon, 300) Rice is classified in the
grass family Gramineae. Its genus is
Oryza and species O. sativa. It is
commonly cultivated for food in Asia. Some
varieties of rice include red
rice, glutinous rice, and wild rice. (Jodon, 303)
The kernel within the
grain contains most of the vitamins and minerals (298).
The kernel
contains thiamine, niacin, and riboflavin (299). Rice has many
enemies that
destroy a majority of the rice crops. The larvae of moth, stem
borers, live
in the stems of the rice plants. Some insects suck the plant juices
or chew
the leaves. Birds, such as bobolink, Java sparrow, or paddybird, would
eat
the seeds or grains. Disease causing factors such as fungi,
roundworms,
viruses, and bacteria also destroy the rice plants. Blast disease
is caused by
fungi which causes the panicles containing the grains to break.
(Jodon, 300)
There are various types of rice grown all over the world. A
majority of rice
grown is cultivated rice. When rice is grown with water
standing on the fields,
it is called lowland, wet, or irrigated rice. Rice
plants grown in certain parts
of Asia, South America, and Africa are called
upland, hill, or dry rice because
they are raised on elevated lands that
cannot be flooded, but with plentiful
rainfall. Wild rice is grown along lake
shores of Canada and the Great Lakes. It
is usually eaten by people in India.
Scented rice is the most expensive because
is has long grains and tastes like
popcorn when cooked. Glutinous rice is waxy
rice consumed by Asians. It is
cooked to a sticky paste and is used for cakes
and confections. (Jodon, 299)
Rice was thought to have originated in southeast
Asia when Alexander the
Great invaded India in 326 B. C(Jodon, 303). Further
research revealed that
rice was cultivated around or at the Yangtze River in
China, around 4000
to 11,500 years ago. One archaeologist, Toyama, surveyed data
on 125 samples
of rice grains, plant remains, husks, and other factors from
numerous sites
along the length of the Yangtze River. "He reported that the
oldest samples.
. . are clustered along the middle Yangtze in Hubei and Hunan
provinces.
Samples from the upper and lower portions of the Yangtze River were
found to
be younger, around 4,000 to 10,000 years old. "This pattern..
.suggests that
rice cultivation originated in the middle Yangtze and spread from
there".
Archaeologists see more than a decade of excavation of the Yangtze
River
and nearby sites to confirm that the Yangtze River is where rice was
first
cultivated. (Normille, 309) The Greeks learned of rice when Alexander
the Great
invaded India around 326 B. C. Spain was introduced to rice when it
was
conquered by the Moors during the 700's A.D. Spain then introduced rice
to
Italy, around the 1400's. The Spanish also introduced rice to the West
Indies
and South America, around the 1600's. Rice was introduced to the
United States
when a Madagascar ship docked in the Charleston, South Carolina
harbor. The ship
captain presented the governor with a sack of seed rice. It
was then grown in
states south of the Ohio River and east of Mississippi.
(Jodon, 303) Rice is
usually grown in lowland fields divided by dirt walls
(Jodon, 300) A majority of
the rice crops are grown with water standing on
the fields (Jodon, 299). On
level land, these paddies and dirt walls are
built in wavy or straight lines. On
hill-like land, they follow the slopes
and form paddies that rise like steps.
The dirt walls are used to hold in
water for the fields. (300) Cultivation of
the rice plant requires
controlling the water supply and weeding the rice
fields. Water must be two
to six inches deep for the seeds to germinate
properly. After the grains
germinate, the water is drained. The rice plant is
then cultivated by hand.
(Jodon, 301) Besides steaming the rice for consumption,
it is also used for
other products. Enriched rice is regular kernels and vitamin
and mineral
coated kernels mixed together. The Japanese use the fermented rice
kernels to
make sake, rice wine. Rice is sometimes used in making beer in the
United
States and Europe. Powdery by-products, bran and polish, are used to
feed
livestock. Starch from the rice plant is used in laundry starch. The
Japanese
usually use the rice hulls to prevent breakage of fragile objects
during
shipping. Rice hulls also serve as fuel for steam engines. The dried
stalks of
rice are used to make sandals, hats, raincoats, and thatching
roofs. In the
Philippines, farmers grow mushrooms on beds of rice straw.
(Jodon, 298-99) The
purpose of the "Super Rice challenge" is to create rice
plants that
are disease resistant, insect resistant, and produces twenty-five
percent more
food per acre. The International Rice Research Institute has
been working on
this challenge. It is competing with many various factors
that are pushing the
International Rice Research Institute to try and
complete the challenge as soon
as possible. Factors such as growing
population, limited areas for growing rice,
and the common farmer's
philosophy of "get anything to grow" are
pushing researchers to complete the
project as soon as possible. Also, the new
varieties of rice has raised a
question of the farmer's health because of the
uses and effects of
agricultural chemicals. Since normal rice grown in paddies
produces high
amounts of methane, the International Rice Research Institute must
also find
a way to create rice plants with a low methane production. Gurdev
Khush
believes that the "super rice" will be ready for farmers to
plant them around
the end of the century. (Bioscience, 239) Researchers were
able to develop a
type of rice during the 1960's. This type of rice, called
"miracle rice",
because of its high yields. Researchers were able to
develop it by combining
a short variety of rice with a tall variety. This
crossbreeding resulting in
a rice plant that can withstand wind and rain and
have a high production
yield. This new breed was thought to have been to reduce
the food shortages
that depend on rice as a staple food, but because of various
conditions in
other countries, this rice plant was not very successful. (Jodon,
299)
Blight, caused by bacteria, spreads rapidly through rice fields in
water
droplets. The rice plant would develop lesions and die in a matter of
days. This
disease could destroy about half of a rice crop. Through genetic
engineering,
the author and her colleagues have been able to introduce
isolated
disease-resistant genes into the rice plants. (Ronald, 100) The
gene, called
Xa21, was discovered by the International Rice Research
Institute, and Ronald
attempted to clone Xa21 from the International Rice
Research Institute variety.
(101) The Cornell group created a genetic map
which showed the location of
hundreds of markers on the twelve rice
chromosomes. Ronald and her colleagues
used this genetic map to locate gene
Xa21 by examining over one thousand rice
plants to "see how often known DNA
markers showed up in conjunction with
resistance to blight". They used
chromosomal swapping and rearranging that
goes on during sexual reproduction.
The more often they saw resistance in the
next generation of rice plants, the
closer they were to locating the gene. (102)
Since rice plants are
defiant in accepting outside DNA, they used a gun that
"shoots microscopic
particles into intact cells", which was developed
by John Sanford of Cornell.
After using this procedure to introduce Xa21 into an
old, but susceptible,
rice plant they exposed the plants to blight. They found
that the plants were
resistant to the blight. Ronald and her colleagues current
goal is to
introduce Xa21 into rice varieties that are agriculturally
important.
(102-03) Current studies showed that rice plants introduced to the
cloned Xa21
gene have become blight resistant. Since farmers prefer to grow
plants that have
adapted to the various climates and conditions, Ronald
stated that "the
genetically engineered versions will be identical to the
original plants except
for the addition of the single cloned gene...". Ronald
and her colleagues
still have to field-test the new varieties for yield,
taste, and hardiness to
confirm that the original adaptations have remain
unchanged. (104) The success
of this project has reached into testing the
process and the gene on other
plants. Scientists hope that Ronald's process
of making the rice plant blight
resistant will work on other plants. They
hope that this process will be
successful on valuable crops, such as citrus
crops. They plan to combine the
gene Xa21 and other disease resistance genes
to enhance the plant's resistance
to disease. The problem with cloning the
Xa21 gene is that it is still
vulnerable to other diseases such as
grassy-stunt and ragged-stunt viruses.
(Ronald, 104) The purpose of Japan's
rice genome project is to fully map the
twelve chromosomes of the rice plant.
Low funding of this project has hindered
the progression of this project.
Since Japan has increased its funding to its
genome project, the rice genome
division can now complete mapping the twelve
chromosomes of the rice plant.
(Normille, 1702) Rice is one of the world's most
important crops because a
majority of the world depends on this as a staple
food. The number of rice
plants planted, however, are greater than the number of
rice consumed. This
is because of various factors that destroy the rice plants
before they can be
harvested for commercial use. Various factors, such as
insects, birds, and
disease, destroy the rice crops. Projects are being
conducted to improve the
rice plant, but researchers encounter various
obstacles. Making the rice
plant disease-resistant to blight may be useful and
valuable, but they must
also find a way to make the rice plant resistant to
other diseases and
viruses such as ragged- stunt. Since Japan has increased its
funds to its
genome projects, they have been able to increase the work on
mapping the
twelve rice chromosomes. Scientists hope that these projects will
be
finished, and that farmers will be using the enhanced genes on their rice
plants
by the beginning of the next century.
Bibliography
"The
Super Rice Challenge." "Bioscience." Apr. 1995 v.45.
pp. 239 Jodon, Nelson.
"Rice." World Book Encyclopedia. 1976, Chicago.
Field Enterprises
Educational Corporation. v. 16. pp. 298-303 Normille, Dennis.
"Rice Genome
Races Ahead." "Science." 5 Dec. 1997. v. 278.
pp. 1702 Normille, Dennis.
"Yangtze Seen as Earliest Rice Site."
"Science." 17 Jan. 1997. V. 275. pp.
309 Ronald, Pamela. "Making
Rice Disease-Resistant." "Scientific
American." Nov. 1997.
pp.
100-105.