Encyclopedia of Grain Science [Vol 2 G-P]

497 Pages·2004·9.011 MB·English

by  C W Wrigley, Harold Corke, Charles Walker

G
GENETICALLY MODIFIED GRAINS AND
THE CONSUMER
JMJones,CollegeofSt.Catherine,ArdenHills,MN, Europe, consumers give lower acceptance ratings
USA when asked about the genetic modification of foods
CIMJones,Minneapolis,MN, USA than when asked the same question using the term
ª2004,ElsevierLtd.AllRightsReserved. ‘‘biotechnology.’’
The greatest advocates for GM foods generally
comefromtheUSAandafewotherselectcountries.
The scientific and governmental leaders in the USA
Introduction
believe that GM foods, when appropriately tested
Consumer opinion about genetically modified (GM) and used, could be a boon for the world in terms
grains and foods ranges from excitement to resolute of food supply, environmental protection, and eco-
fear. Somewhere in the middle lies the consumer nomic development. Consumer acceptance was
majority. If consumers have heard of GM food, slowlyincreasinguntiltheStarlinkdebacleoccurred.
they have mostly heard contradictory snippets from Starlink corn was approved for use in animal food.
Malthusian and humanitarian discourses calling for It was not approved for use in human food because
biotech solutions that could help feed the world to regulatorswantedfurthertestingtoensuretherewere
the apocalyptic sounding ‘‘Frankenfood,’’ which like noallergyrisks.Mostconsumersfailedtounderstand
Mary Shelley’s 1818 novel evokes the dangers asso- this and assumed that the recall of the product
ciatedinmessingwithnature’sorder.Intheend,the meantitwasunsaferatherthanmerelynotreceiving
ultimate success or failure of GM grains will not final approval. Now that the brouhaha has died
depend on laboratory or farm research successes, down, there is again slowly growing acceptance.
but on consumer acceptance. This article covers the The voices of Europe, led by France, take a more
following: (1) the range of world consumer opinion skeptical approach and possibly trade protectionist
concerningGMgrainsandfoodsand(2)anassessment approach. Scientific and governmental leaders in
ofthefactorsinvolvedinformingthoseopinions. Europe do not completely reject GM foods, but in-
stead believe they have not been proven safe and
therefore invoke ‘‘the precautionary principle.’’ This
Consumer Perception of GM Grains
helps protect their markets. Interestingly some
and Foods
countries are more accepting of GM crops than
they are of the food. This seems to be somewhat
Much of the world has never heard of GM foods or
contradictory (Table 2).
grains.Eveninthebestcases(developednationsthat
The opinions of the governments in the rest of the
have active campaigns and education movements on
world fall somewhere in between those of USA and
both sides of the spectrum concerning GM foods),
Europe, with data for developing nations still quite
polls only show that 70% of consumers are familiar
scarce. It is not surprising that consumer perception
withGMfoods.Inmanycases,theawarenessandac-
generally follows the advice of their scientific and
tual knowledge or willingness to learn more is much
political leaders. Thus, consumers in the USA are
smaller(aslowas25%insomesurveys).Table1gives
far more accepting of the idea of GM foods than
somecomparativedataforsomecountriesinEurope.
the rest of the world.
When consumers in the world hear of GM foods,
their perception could be grossly summarized as
Developing Nations
wary.Ofcourse,thespectrumofopinionvariesdras-
tically across geographical, economic, political, and A2000studypublishedinScientificAmericanshows
social lines. Interestingly, both in the USA and that globally developing nations account for about
2 GENETICALLY MODIFIED GRAINS AND THE CONSUMER
Table1 AwarenessandknowledgeofbiotechnologyinselectedcountriesinEurope
%Whotalk %Whowould Meannumber Knowledge %Engaged
aboutitat readorview ofknown (meancorrect inthe
leastsome tolearnmore applications scoreoutof10) process
Denmark 50 77 2.23 6.60 47
Finland 43 68 1.71 6.21 31
France 37 80 1.76 5.70 29
UK 23 67 2.00 5.90 26
Germany 40 72 1.78 5.30 25
Ireland 18 64 1.50 4.86 18
Spain 24 41 1.70 5.02 15
Europe,overall 32 68 1.79 5.46 25
AdaptedfromGeorgeetal.(2002)Eurobarometer58.0.EuropeansandBiotechnologyin2002.Luxembourg,OfficeforOfficialPublicationsofthe
EuropeanCommunities.Brussels,EuropeanCommission,ResearchDG,2002(http://europe.eu.int/comm/public_opinion/archives/eb/ebs_177_en/pdf).
Table2 SupportforGMcropsandfoodinselectedEuropean to die than to make the entire national food supply
countries unhealthy. This shows the extent of pervading fear
about this technology.
CountrieswhichsupportbothGMcropsandfood
LeadersandscientistsinSouthAmericaseemalittle
Spain(strongsupport)
more welcoming of GM food. Argentina, for exam-
Portugal
Ireland ple, is the second largest adapter by acreage of GM
Finland foodcropsintheworld.InSouthernVoices:AnOn-
CountrieswhichsupportGMcropsbutnotGMfood line Debate on Biotechnology and Food conducted
Belgium in 2001 by the Network University in The
Germany
Netherlands, scientists and leaders from developing
Netherlands
nations gave their opinions on biotechnology. Many
UK
Latin American nations (as well as other developing
CountrieswhichsupportneitherGMcropsnorfood
nations) were excited about the prospects of GM
Sweden
Denmark food, but favored a type of ‘‘open source’’ biotech-
Germany nology, in which patent protection would not create
France(strongopposition) a dependency on developed nations.
Greece(strongopposition)
India To date, there has been no comprehensive
AdaptedfromGeorgeetal.(2002)Eurobarometer58.0.EuropeansandBio-
study of how Indians feel about GM foods, but sci-
technologyin2002.Luxembourg,OfficeforOfficialPublicationsoftheEuro-
peanCommunities.Brussels,EuropeanCommission,ResearchDG,2002 entific and government officials are trying to jump
(http://europe.eu.int/comm/public_opinion/archives/eb/ebs_177_en/pdf).
start biotechnology in India. At the Bangalore Bio
one-quarteroftheareaemployedforGMcrops.Pro- 2003 conference, a majority of Indian scientists
ponents of GM foods usually cite the developing came out in favor of GM foods, arguing that the
world as the greatest potential benefactor of GM number of infant deaths (61 out of every 1000 die
foods, yet studies of what the people in developing from disease and hunger) could be reduced with
countriesthinkofGMfoodsarefewarefarbetween. GM foods. However, the scientists argued that GM
One of the great worries among GM food oppo- foodsshouldberesearched,produced,andapproved
nents is the potential to create further economic im- inIndiasotheywouldnothavetorelyontheWestfor
balance between the impoverished and wealthy suchtechnology.TheyarguedthatrichEuropeanna-
countries. So while many developing nations look tions have the luxury of choosing not to accept GM
at GM food, especially grains, with a keen eye to- foods, but in countries like India the acceptance of
wards solving many health and hunger issues, many biotechnology ends up as a choice between feeding
leaders in developing nations fear that GM food and not feeding people.
would not move their countries towards economic
self-sufficiency. Africa Similar to the resistance to GM food in
In fact, in 2002, the African nation of Zambia Zambia,thegovernmentsofZimbabwe,Mozambique
rejected a deal proposed by the USA in which they and Botswana all initially protested the introduction
would accept GM grain from the International ofGMfoodcropsintotheircountries,buteventually
Federation of the Red Cross. In a statement, the relented. However, African nations worry about
Zambian government said it would prefer its poor GM foods. An international campaign is currently
GENETICALLY MODIFIED GRAINS AND THE CONSUMER 3
underwayinMalawitoreject250000metrictons(t) University on New Zealanders’ attitudes towards
of GM maize. The latest reports, however, indicate GM foods, found the country split in half between
that most of the Malawian farmers have decided to thosethatfavoredGMfoodsandthosethatopposed
ignorethewarningsandplantthemaize. them. New Zealand also seems to show indications
In a different development, in March 2003 South of a very polarized country, with 25% of the 908
African consumers started a campaign for GM food responders having extreme negativefeelings towards
labeling, indicating that consumers in South Africa GM foods and 18% having very positive feelings
areawareofGMfoodsandwanttherighttochoose towards them.
between eating them or not. The study also showed some interesting demo-
graphic differences. Young (18(cid:1)24 years) and male
Pacific Nations groups were the most likely to support GM foods,
whereas older (35þ years) and female groups were
It may be stated that major nations on the Pacific,
morelikelytoopposethem.Thestudyalsoindicated
including Australia, New Zealand, Japan, China,
stronger approval for GM foods in urban over rural
and India provide a glimpse of the middle ground
areas.
in this debate. Though varied in their opinions,
New Zealand’s scientific, governmental, and agri-
these nations seem to be the moderates in the GM
cultural communities are still very cautious over the
food debate (cid:1) cautious, yet accepting. In countries
useofGMgrainsoroilseeds.However,inMay2003,
like Australia and New Zealand, consumers seem
New Zealand joined a World Trade Organization
evenly split in the debate over GM foods. And
(WTO) disputes case against the European Union
while no one is yet allowed to produce GM foods
(EU) because of its refusal to open markets to GM
for public consumption in Australia and New
foods. This does not imply that New Zealand
Zealand, both countries are actively researching the
supports the production or trade of GM foods, but
production of biotech food crops.
that the government believes in a trade system that
Like in Europe, most governments in Asia have
setshealthandenvironmentalstandardsbasedonsci-
not given the go-ahead for GM food crop produc-
entific evidence and risk analysis.
tion, but according to a 21 February 2003 article in
the New York Times, other major Asian countries,
China In2001,Chinaimplementedastrictlabeling
including Japan, Thailand, The Philippines, and
policy on GM soybeans. The reason given for the
Malaysia, have set aside billions of dollars for
move was public outcry and safety. Some think the
research on biotech crops. The same article reports
labeling requirement may have been less about pub-
thatChinaissofaraheadinitsresearchonGMfood
lic perception or fears, and more about economic
cropsthatitstandstodominatetheregioninagricul-
protectionism.
tural production if GM food gains acceptance.
China has halted the commercial production of
biotech food crops that had already been approved
Australia A 2001 survey of Australian consumers due tooppositionfrom major trade partners. Never-
conductedbythegovernmentagency,Biotechnology theless, despite the labeling and export concerns,
Australia, showed a growing acceptance of biotech- China remains the world’s second largest spender
nology,from28%in1999to35%in2000to49%in on GM food research (US expenditure stands at
2001. The strongest acceptance among consumers $1.5 billion).
was for GM foods that might induce health benefits
(lower cholesterol, reduction in allergens etc.). The Japan Surveys in 2001 showed that Japanese con-
survey showed lowest consumer acceptance of sumersappearlessready toembrace GMfoodsthan
foods engineered to ward off pests or improve taste. other Pacific nations. The Biotechnology Strategy
Australianagenciesarenottotallyconvinced,how- Council, a government agency erected in July 2002,
ever. InMay2003,despitetheoverallriseinaccept- was partially conceived to fight this perceived prob-
ance for GM foods, Victoria, a southern Australian lem.Oneofitsprimarygoalsistoeducatethepublic
state, joined the rest of Australian canola producing about the issues surrounding biotechnology.
statesbyhaltingthereleaseofGMcanolaforatleast
another year. GM canola was to be Australia’s first European Nations
GM food crop.
A study conducted by the American Association for
the Advancement of Science in 1999 looked at the
New Zealand A 1999 study, conducted by Hort- difference between European and US perceptions
Research in collaboration with AgResearch, Forest overGMfoods.Asimilarstudy,theEurobarometer,
ResearchInstitute,AucklandUniversity,andMassey conducted every two to three years (most recently in
4 GENETICALLY MODIFIED GRAINS AND THE CONSUMER
2002 (cid:1)‘‘Europeansandbiotechnologyin2002’’)by a 2000 study by Cal Poly State University, showed
The European Commission breaks down the various aslightmajorityopposedGMfoods.Thiseitherfalls
European opinions on biotechnology issues. Both in the bounds of survey error or suggests a growing
studies show a wide gulf between US and European acceptance of GM foods.
acceptance of GM foods.
Seventy-one percent of the 16500 consumers Scandinavia (Finland, Denmark, Norway, Sweden,
interviewed in EU countries for the Eurobarometer andTheNetherlands) AmongtheEUcountries,the
responded that they did not want to consume GM Scandinavian countries are the most engaged in GM
foods. This contrasts with a commonly quoted rate food research. While most Scandinavian countries
of (cid:2)70% acceptance rate by US consumers. While still have a majority of consumers opposed to GM
still in the minority, the Eurobarometer showed foods, consumers in the Scandinavian countries are
thatEuropeanstudents,youth,higherincomepeople, the most supportive (as a group) of GM foods. The
and men had a higher acceptance rate of GM percentages are closer to an even split among the
foods, whereas, lower income people, the elderly, countries,comparedtothe71%EUrejectionaverage.
and women rejected GM foods at a much higher
Western Europe (Germany and France) In France,
rate than the survey average.
apopulation particularlyhostile towards GM foods,
much of the public perception can be traced to two
EU candidate countries According to the Euroba-
factors: first, France’s age old traditions celebrating
rometer,candidatecountries(Slovenia,CzechRepub-
food as an important cultural placard; and second,
lic, Slovakia, Turkey, Malta, Romania, Lithuania,
a strong grassroots campaign against GM foods
Estonia, Hungary, and Cyprus) survey responses
conductedbyaseriesofwell-receivedenvironmental,
about attitudes to GM food reflect the opinions in
consumer, economic, and political organizations.
theEU.Fifty-twopercentofthosequeriedinthecan-
Consumers in Germany do not go as far as the
didate countries (compared to 56% in EU countries)
French, but a large majority of Germans align with
viewed GM foods as dangerous.
the French on this issue.
Southern Europe (Italy, Greece, Portugal, and
NorthAmericanNations
Spain) A study of 252 food shoppers in Modena,
Italy during the Fall of 2001 conducted by Cal Poly NorthAmericansarethegreatestproponentsforGM
StateUniversityinCaliforniashowedthat only28% foods in the world, and consumers reflect the opin-
of the consumers queried in Italy knew what GM ions’ of scientists and leaders. Multiple surveys bet-
foods were. Only 43% of the shoppers queried said ween2001and2003showavaryingdegreeofpublic
they would even consider purchasing GM foods. acceptance, from a low of 32% to a high of 71%.
The2002EurobarometershowedthatGreecewas Evenwiththevaryingdegreeofsampleresults,most
one of the four countries (France, Austria, and surveys do show a majority of Americans and Cana-
Luxembourg) that was particularly hostile to GM dianssupportandaccept GMfoods.Caribbeancon-
foods. In contrast, the 2002 Eurobarometer showed sumersaccordingtoa2001surveywerelessaccepting
that Spain and Portugal were two of only four of GM foods and grains than their North American
countries in Europe (joining Ireland and Finland) counterparts.
that showed overall support for GM foods. April2003studiesconductedbytheUniversitiesof
CalgaryandAlbertashowCanadianconsumerssup-
British Isles England and Scotland share an overall portGMfood(52%),butapprovalhasdeclinedover
disapproval for GM foods. In separate studies for thepast6years.Thestudyalsoshowsthatmorethan
the two countries in 2003 (Mori Environmental half of consumers surveyed would buy GM foods if
Research Bulletin and Public Perceptions of Food they were cheaper than nonmodified foods. Seventy-
and Farming in Scotland), about 56% of consumers five percent of Canadians want all GM food to be
in each country were against GM foods, just slightly clearly labeled.
lessthantherestofEurope.Only14%oftheEnglish According to surveys conducted in the USA, 70%
surveyed would themselves buy GM food products. have heard or read about biotechnology but there is
Consumers in the Scottish survey stated they would arangeofopinionsaboutGMfoodsandgrains.Like
neither buy food labeled as ‘‘GM,’’ nor actively seek Canadians, over 85% of US consumers want these
out additional information. products labeled. US consumers respond with the
Ireland was more supportive of GM food. A greatest acceptance when queried about specific
majority of the consumers supported GM foods applications. For example, 75% of US consumers
according to the 2002 Eurobarometer. However, believe that GM grains can help solve world hunger
GENETICALLY MODIFIED GRAINS AND THE CONSUMER 5
andworldmalnutrition.USconsumersrespondwith a comparison of US and UK consumers, 76% of US
moreresistancewhentheyareaskedabouttheirper- consumerstrustedthegovernment’srole‘‘insecuring
sonal choices or beliefs. In a 2001 survey conducted the safetyof general food supply.’’ Only 48% of UK
byBIGresearchonly23%ofrespondentsansweredin consumers felt that same way. The Eurobarometer
the affirmative to questions of ‘‘Would you eat GM showed similar feelings (cid:1) only 32% of respondents
foodproducts?’’and‘‘IsGMfoodsafetoeat?’’About felt that ‘‘public authorities can be trusted to make
halfwereundecidedandabout30%answeredinthe good decisions on GMOs.’’
negative. Furthermore, in a 2001 ABC News poll,
57% of US consumers said they would be less likely Labeling
to purchase a product labeled GM.
One of the major battlegrounds in terms of public
trust is the issue of labeling. In almost every survey
upwardsof85%(andsometimesupto98%)ofpeo-
Factors Influencing
ple want GM foods labeled clearly. Most consumers
Consumer Perception
believe they have the right to know what they are
Social, economic, and political factors contribute to eating and have the right to choose not to eat GM
consumeropinionsaroundGMgrains.Understanding foods if they are uncertain about them. The accept-
ofeachofthesecontributestothesuccessorfailureof ance rate for GM food rises significantly in most
GM foods. Nine key factors contribute to consumer surveys if all GM foods were to be clearly labeled.
opinion about GM grains: use; scientific literacy;
trust in regulatory organizations; labeling; safety Safety
(environmental and health); perception of benefit;
Underlying ideas of trust, labeling, literacy, and use
price;religion;andglobalandsocio-economicissues.
istheconsumer’suncertaintyabouttheenvironmental
and consumptive safety of GM food. According to
Use
severalsurveys,ifaconsumerhasheardofasetback
Thebiggestfactorwhenitcomestoconsumerpercep- or problem with GM food production or consump-
tion is the understood use of biotechnology. Among tion(regardlessofwhethertheconcernshavevalidity
usesforbiotechnology,geneticmodificationforfood ornot),theyarefarmorelikelytorejectGMfood.
andfoodgrainsusuallyfallssomewhereinthemiddle Itwouldseemthatthemediawouldthusplayahuge
of the spectrum in terms of acceptability, far below roleinthereceptionofGMfood.Surprisingly,astudy
the acceptance of medical uses. Furthermore, con- ofmediacoverageshowedthattheGMfoodsarepor-
sumers differentiate uses within the realm of GM trayed in a more positive light in Europe than in the
grains. Consumers find GM grains that reduce USA. However, pro- and anti-GM food campaigns
allergens or pesticides far more appealing than GM continuetobearguedprimarilythroughthemedia.
foods providing better taste or nutrition. This also MediacoverageoftheStarlinkcornissuecertainly
suggeststhatmanysurveysmayhaveflawsifpotential polarizedpublicopinionintheUSAatthetimeofthe
use remains unspecified. recall.Inthiscasethemediadidlittletoexplainthat
the product was recalled not because it was unsafe,
Scientific Literacy
but rather because it had only received approval for
AnothermajorfactorinconsumeracceptanceofGM animal, not human food.
grains may be scientific literacy. Some surveys have
shown that people who understand the concepts of Perception of Benefit
DNA and gene splicing are more accepting of GM Formanythereisaperceptionthatonlyagribusiness
foods. However, a major 1999 study conducted by benefits.Farmersbenefit bybeing abletogrowmore
the American Association for the Advancement of grainon less space, to improve resistance toweather
Science, compared scientific and genome literacy in and disease, and to reduce or eliminate the use of
Europe and the USA. While the European consumer herbicides and pesticides. While these all reduce the
scoredsignificantlyhighercomparedtotheirUScoun- farmer’s cost and increase profit, consumers fail
terpart in terms of genome knowledge, they showed to realize that they also benefit by having less land
much greater mistrust of GM grains and foods. devoted to food and grain production. Many con-
sumers fail to consider environmental benefits from
Trustin Regulatory Organizations
lesspesticideandherbicidesprayingandwaterquality
European consumers also have greater mistrust for benefits with decreased pesticide runoff. Until con-
a large number of scientific and regulatory bodies sumers actually believe and see that rice can have
that come out in favor of the safety of GM food. In more vitamin A, sorghum with more available
6 GENETICALLY MODIFIED GRAINS AND THE CONSUMER
mineralsandfewertoxicfactors,protein,wheatwith- among consumers according to a Pew Initiative on
out the protein sequence that causes gluten intoler- Food and Biotechnology study conducted in 2001.
ance,andgrainsthatarelessallergenic,therewillstill The study, conducted among people of faith in the
be large pockets of consumer resistance. USA, showed that in the USA people of faith
Golden rice is perceived by many as an example supportedbiotechnologylessthantherestofthepub-
of biotechnology’s promise. Every year, over half lic. It showed that the highest approval rating for
a million children in developing countries suffer biotech was among Jews (55%), followed by Catho-
frompreventableblindness.Ricehasbeengenetically lics (42%), Protestants (37%), and Muslims (32%
engineered to contain the carotenoid precursor of approved). The number one reason respondents
vitaminA.Thisgeneticallyengineeredriceisreferred said they disapproved of biotechnology is that man
to as ‘‘golden rice’’ because of its yellowish color. In shouldnotbeplayingGod.(Thesestatisticsexistde-
2001 two biotechnology companies, Greenovation spiteapprovalforGMfoodbymanyexpertethicists,
andSyngentaofferedtheGMricetosmall-scalefarm- including the Nuffield Foundation, the Church of
ersindevelopingcountriesfreeofchargeandwithout England and even the Vatican.) Unlike groups of
limitations for humanitarian purposes. Because rice consumers that may be swayed by more scientific
is already a staple crop in developing countries, the proof to the safety of GM food or a system of food
vitaminAcontainingricewouldallowpeopleinsuch labeling, those with moral objections to GM food
areas to obtain more dietary vitamin A and potent- may never be swayed to accept GM food.
ially reduce blindness and other effects of vitamin A
deficiency. Economics/Concentration ofPower/SES
Interestingly, golden rice set off a major debate. Socio-economic status (SES) is also amajor factor in
Activist groups such as Greenpeace have tried to determining what consumers think of GM food
discredit the gesture by stating that the rice will and grains. Regardless of the overall sentiment in a
not provide enough vitamin A and that it will fail particularcountry,mostsurveysshowthatconsumers
to address blindness because of other malnourish- inhigherSESbracketsacceptGMfoodwithfarmore
ment. The Rockefeller Foundation, a funder of the regularitythanthoseinlowerSESbrackets.
developmentofgoldenrice,saysthatthecalculations Many consumer groups and policy makers are
of the activist groups about the amount of rice that concerned that GM food will create an even greater
needs to be eaten to address the vitamin A problems inequity between developed and developing nations
are based on some of the first versions of the rice because developing nations will have to purchase
and are not accurate for more currently available expensive GM seeds from Western companies. Fur-
rice with greater vitamin A levels. The issue of thermore, farmers in the US and elsewhere have
golden rice has even split members of Greenpeace expressed concern over using GM seeds even if it
intothosewhoopposethetechnologyunderanycir- will save them money in production because many
cumstances and those who believe that this rice has countries either have strict labeling requirements
a useful purpose and do not want to oppose the or outright bans on GM food. Public perception is
humanitarian effort. waiting to see how the economics of GM food
bears out. If the industry fails to convince farmers
Price in developed nations that they can sell the product
or in developing nations that the industry can
Two contradictory studies show that product price
servicethemwithout disruptingthe localeconomies,
may or may not be important to consumers. A
theywillfurtherimpairtheirimageamongthepublic.
Canadian study asked whether consumers would
GM grains offer potential for improved yield and
buy GM food if it were significantly cheaper and
nutritional advantages. With careful balancing of
tasted the same. A majority of respondents said
environmental and ethical issues, vigilance about
that they would. In a separate study conducted by
allergiesandothersafetyissues,clearconsumeredu-
the University of Southern Illinois 56% of UK con-
cation and awareness of sharp cultural differences
sumers and 37% of US consumers said that they
surrounding GM grains, the potential benefits of
would be willing to pay a premium for non-GM
this technology can be harvested.
breakfast cereals. Only 22% in each country said
that they would not be willing to do so.
See also: Consumer Trends in Consumption. Food
Religion/Morality Safety through the Production Chain. Fortification
of Grain-Based Foods. Genomics. Labeling of
There has not been much research on religion and Grain-Based Foods. Nutraceuticals from Grains.
GM food acceptance, but it remains a key factor Nutrition:Beriberi,ADeficiencyRelatedtoGrains.
GENOME MAPPING 7
Further Reading McHugenA(2000)Pandora’sPicnicBasket:ThePotential
and Hazards of Genetically Modified Foods. Oxford:
Bauer MW, Durant J, and Allum NC (1999) Worlds OxfordUniversity Press.
Apart?TheReceptionofGeneticallyModifiedFoodsin Moon W and Balasubramanian SK (2001) Public Percep-
Europe and the US. Washington, DC: American tion and Willingness-To-Pay a Premium for Non-GM
Association forthe Advancementof Science. Foods in the US and UK. Carbondale, IL: Southern
BrownK(2001)Geneticallymodifiedfoods:aretheysafe? Illinois University.
ScientificAmerican 284(4): 51(cid:1)65. PEW (Pew Initiative on Food and Biotechnology)
BruhnC(1999)Consumerperceptionsandconcernsabout (2002) Results of several surveys of Americans on
food contaminants. Advances in Experimental Biology questions pertaining to agricultural biotechnology
andMedicine 459:1(cid:1)7. ( www.pewagbiotech.org ).
Bucchini L and Goldman LR (2002) Starlink corn: a risk Taylor SL and Hefle SL (2002) Genetically engineered
analysis.EnvironmentalHealthPerspectives110:5(cid:1)13. foods: implications for food allergy. Current Opinions
Fischhoff B and Fischhoff I (2000) Publics’ opinions in Allergyand ClinicalImmunology2:249(cid:1)252.
about biotechnology. AgBio Forum vol. 4 (3&4), TrewavasA(2002)Malthusfoiledagainandagain.Nature
Col. 2, http://www.agbioforum.org. 418: 668(cid:1)670.
Gaskell G (2000) Agricultural biotechnology and public Thomson JA (2002) Research needs to improve agricul-
attitudesintheEuropeanUnion.AgBioForum3:87(cid:1)96. tural productivity and food quality, with emphasis on
George G, et al. (2002) Eurobarometer 58.0. Europeans biotechnology. Journalof Nutrition132:3441S(cid:1)2S.
and Biotechnology in 2002. Luxembourg, Office for Zimmermann MBandHurrellRF (2002)Improvingiron,
Official Publications of the European Communities. zinc and vitamin A nutritionthrough plant biotechnol-
Brussels, European Commission, Research DG, 2002. ogy. CurrentOpinionsin Biotechnology13: 142(cid:1)145.
( http://europe.eu.int/comm/public_opinion/archives/eb/
ebs_177_en/pdf ).
IFIC (International Food Information Council Federation)
Relevant Websites
(2002)USConsumerAttitudesTowardsFoodBiotech-
nology. Washington:IFIC(online). http: //www.ag biofor um.org.
King J (2002) Biotechnology: a solution for improving
http: //europa. eu.int.
nutrient bioavailability. International Journal of Vita-
http: //www.nc bi.nlm .nih.gov.
minand NutritionResearch 72: 7(cid:1)12.
http: //www.ag biotechn et.com (cid:1) AgBi otechNet .
Lonnerdal B (2003) Genetically modified plants for
http: //www.ge nengnew s.com/top1 00.asp.
improved trace element nutrition. Journal of Nutrition
http: //www.wh ybiotech. com.
133(5 suppl.1):1490S(cid:1)3S.
Mazur BJ (2001) Developing transgenic grains with im- http: //biotech. icmb.utex as.edu.
provedoils,proteinsandcarbohydrates.NovartisFoun- http: //pewagb iotech.o rg.
dationSymposium 236:233(cid:1)239 (discussion240(cid:1)1). http: //www.e rs.usda. gov/amb erwaves .
GENOME MAPPING
J DFaris,USDA-ARS,Fargo,ND, USA theymaybetoageneorregionofinterest.Thereare
BFriebe andB SGill,KansasState University, two types of genome mapping (cid:1) physical mapping
Manhattan, KS,USA andgeneticlinkagemapping(cid:1)inwhichdistancesare
PublishedbyElsevierLtd. measured in terms of base pairs and recombination
frequency, respectively.
Genetic markers are differences in the DNA
Introduction
sequenceofchromosomesderivedfromtwodifferent
Genome maps are very similar to road maps except parents, and these polymorphisms can be visualized
that, instead of traversing across land, they traverse in several different ways. Morphological markers
across the chromosomes of an organism. Genetic arevisiblemarkers,whichcanbeidentifiedbysimply
markersserveas‘‘landmarks’’alongthechromosome observing the phenotypes of individuals. Isozymes
and provide researchers information as to how close are protein variants which, after separation by
8 GENOME MAPPING
electrophoresis, can be visualized by a colorimetric cleave the DNA at that site. In restriction fragment
activityassayfortherelevantenzyme.DNAmarkers assays,asinglenucleotidedifferingbetweentwogeno-
are visualized bychemicalstaining oftheDNA itself types can result in a genetic marker when the base
or by fluorescence; they can also be labeled with substitutionresultsintheabolishmentofaparticular
a radioisotope and then visualized by autoradiogra- restriction site and, thus, a larger fragment in one
phy. Genetic polymorphisms can also be monitored genotype compared to the other (Figure 1a). This
by direct sequencing of the DNA itself. Currently, results in a discrete marker representing an indivi-
markers of choice are DNA-based markers because dual’s genotype that follows the laws of heredity
of their universal applications, information content, and can be screened in the progeny. In polymerase
and ease of automation, and these will be discussed chainreaction(PCR)-basedassays(seebelow),asin-
in detail. gle base substitution within a primer annealing site
can render the site noncomplementary and prohibit
thefragmentfrombeingamplified(Figure1b).Geno-
Molecular Basis of DNA Markers
typeswithorwithouttheparticularbasesubstitution
DNAmarkersreflectdifferencesintheDNAsequen- can be distinguished by the absence or presence of
ces of two parents of a mapping population. These an amplicon in PCR-based assays. Thus, single base
differences, or polymorphisms, can arise through substitutions are specific to particular restriction en-
mutations resulting in a single nucleotide difference, zymes or PCR primers. Rearrangements of the DNA
errorsinDNAreplication,orinsertionsanddeletions betweentworestrictionsites,ortwoprimerannealing
of larger tracts of DNA. Restriction enzymes are sites,canalsogenerateDNAmarkers(Figures1cand
used routinely in molecular biology and genomics. 1d). Such rearrangements can usually be detected
RestrictionenzymesrecognizespecificDNAsequence using several different restriction enzymes or PCR
palindromes, usually 4, 6, or 8bp in length, and primer sets that flank the rearranged region.
(a) (b)
RFLP Autoradiography PCR Gel electrophoresis
probe primer
A B A B
A A
B B
bp substitution
elimination of bp substitution
restriction site elimination of primer
annealing site
(c) (d)
RFLP Autoradiography PCR Gel electrophoresis
probe A B primer A B
A A
B B
DNA insertion resulting DNA deletion
in a larger restriction resulting in a smaller
fragment amplified fragment
Figure1 ThemolecularbasisofDNAmarkers:(a)TheDNAoftwogenotypes(AandB)isdigestedwitharestrictionenzyme,which
recognizes specific sequences (arrowheads). An RFLP probe, which is a short fragment of DNA, hybridizes to complementary
sequencesintheA andBgenotypes.ThefragmentdetectedbytheprobeingenotypeBis largerthanthatdetectedingenotype
A,becauseasinglebase-pairsubstitutionhaseliminatedoneoftheflankingrestrictionsites.Thesizedifferencesofthehybridizing
fragmentsarevisualizedas‘‘bands’’byautoradiography.(b)PCRanalysisofatargetsequenceingenotypesAandB,whereasingle
base-pairsubstitutionhasoccurredwithintheannealingsiteoftherightprimeringenotypeBresultinginthelackofannealingand,
therefore,theabsenceofanampliconwhichisviewedaftergelelectrophoresis.(c)RFLPanalysisofgenotypesAandB,wherethe
detectedfragmentinBhasundergoneaninsertionofaDNAfragmentcreatingalargerrestrictionfragmentthanthatinA.(d)PCR
analysisofgenotypesAandB,wheregenotypeBhasundergoneadeletionofafragmentofDNAbetweenthetwoprimingsitescreating
asmallerampliconthanthatinA.
GENOME MAPPING 9
Methods of Visualizing DNA Markers DNAfromwhichatargetfragmentistobeamplified
is mixed together with the primers, nucleotides, and
DNA markers can be detected in several different
anenzymethatpolymerizesDNA(usuallyTaqpoly-
ways, some of the most common being restriction
merase). In the PCR process, the samples are first
fragment length polymorphisms (RFLPs), random
heated to 94(cid:1)96(cid:2)C to denature the double stranded
amplified polymorphic DNAs (RAPDs), amplified
target DNA. For the second step, the temperature is
fragment length polymorphisms (AFLPs), sequence
lowered to 50(cid:1)65(cid:2)C for one to several minutes al-
tagged sites (STSs, also known as cleaved amplified
lowing the left and right primers to anneal to com-
polymorphicsequences(CAPS)),microsatellites(also
plementary sequences on the target DNA. For the
knownassimplesequencerepeats(SSRs)),andsingle
third step, the temperature is raised to 72(cid:2)C for
nucleotide polymorphisms (SNPs).
one to several minutes allowing the Taq polymerase
RFLPs are detected by hybridizing a labeled DNA
toattachateachprimingsiteandextend(synthesize)
probe, a short piece of DNA usually 0.2(cid:1)2.0kbp in
a new DNA strand. These three steps constitute one
length, togenomicDNA thathasbeendigestedwith
cycle.When30cyclesareperformedinsuccession,the
a restriction enzyme, separated through an agarose
exponential amplification of fragments will result in
gel,andtransferredtoanylonmembrane.Hybridized
over one billion copies of the target fragment. Once
fragmentsarethenobservedas‘‘bands’’byautoradi-
the PCR is complete, samples are electrophoresed
ography in cases where probes are radioactively
through an agarose or polyacrylamide gel, stained
labeled (Figure 2a). RFLPs were the first type of
with a chemical, and visualized by UV light or
DNAmarkersusedthatcouldbeappliedtoessentially
other means (Figure 2b).
any organism, and they are still used routinely in
RAPD markers are detected using short (10mer)
applications such as comparative mapping, map-
randomoligonucleotidesasprimerstoamplifygeno-
based cloning, etc. Nonradioactive labeling proto-
mic DNA sequences. RAPDs have not been widely
cols are now available and used to some extent,
used for genomic mapping because of the unpredict-
whichhaverenderedRFLPsmoreuserfriendly.How-
able behavior of the short primers in PCR reactions,
ever, due to their relatively low-throughput capabil-
which leads to low repeatability.
ities, the more user-friendly PCR-based markers are
TheAFLPtechniquecombinestheuseofrestriction
now preferred for generating whole genome maps.
enzymeswith PCR. To detectAFLPs, genomicDNA
RAPDs,AFLPs,STSs,microsatellites,andSNPsare
is digested with two restriction enzymes simulta-
allPCR-basedmarkers.PCRmarkersrelyonthede-
neously and oligonucleotide adapters are ligated to
velopmentofaspecificoligonucleotide,orprimer,to
the ends of the fragments to serve as priming sites.
serve as a start site for amplification. The template
Oligonucleotide primers having from one to three
selective nucleotides in addition to the adapter se-
quence are used in PCR amplification, and the frag-
ments are separated on a polyacrylamide gel. To
(a)
visualize AFLPs, one primer is end-labeled with ra-
dioactivity or fluorescence, or the DNA fragments
are directly stained with chemicals. AFLPs provide
a very high throughput method for identifying
DNA markers as multiple markers can be identified
with each restriction enzyme/primer combination.
In theory, the number of markers potentially identi-
(b) fiable by AFLP is virtually unlimited, because they
are limited only by the number of restriction
enzyme/primer combinations surveyed.
Microsatellites consist of di-, tri-, or tetra-nucleo-
tiderepeats,andDNAsequencesflankingtherepeats
areusedasprimingsitesinPCRreactions.Theseshort
tandemly repeated sequences tend to be imprecisely
replicated during DNA synthesis. As a result, the
number of repeats within a microsatellite tends to
Figure 2 (a) RFLP fragments detected by autoradiography. be highly variable even among members of the
(b)PCRampliconsdetectedbyagarosegelelectrophoresisfol-
same species. Therefore, microsatellites tend to pro-
lowedbystainingwithethidiumbromideandvisualizationunder
duce a high degree of polymorphism. Although
UVlight.Thetwolanesmissingtheampliconaregenotypespos-
sessingdeletionsofthetargetsequence. microsatellites are costly to identify because of the
10 GENOME MAPPING
amountofsequencingrequired,oncespecificprimers mapping,marker-assistedbreeding,andevolutionary
are constructed they are very user friendly and studies (for further related readings, see Genomics).
efficient. Genetic mapping relies on the fact that nuclear
STSmarkersareusuallydetectedusingPCRprim- genomesaremadeupofchromosomes,whichcontain
ers designed on the basis of sequenced RFLP clones both genes and noncoding DNA. When homologous
that have previously been mapped. Genomic seq- chromosomespairatmeiosis,theyrecombineatvar-
uences amplified using STS primers are usually iouspositionsalongthechromosomes.Thus,recom-
digested with a four-base cutter enzyme to reveal binationisthebasisforgeneticlinkagemappingand
polymorphisms. STS markers are also very user determining the order of markers along the chromo-
friendlyandtendtobehighlyreproduciblecompared some,i.e.,markersareseparatedbygeneticdistances
to methods based on arbitrary primers due to the calculated based on the amount of meiotic recombi-
larger primers and increased specificity. Also, STSs nation that occurs between them.
can be selected based on prior knowledge of the An example of genetic linkage mapping of
map position of the corresponding RFLP probe. three linked markers in 20 F progeny is presented
2
SNPs are the most common type of genetic differ- in Figure 3. The markers include two DNA markers
encebetweenmembersofthesamespecies.AnSNPis (A and B) and one morphological marker (disease
a single base-pair difference at a specific site in the resistance gene ‘‘R’’). The DNA markers are co-
DNA. There are many ways of identifying SNPs. dominant and, therefore, all possible genotypes can
Currently, most procedures involve target sequence be determined in the F progeny (homozygous for
2
PCR amplification followed by electrophoresis, parent A, homozygous for parent B, and heterozy-
sequence detection, or mass spectrometry. gous). For the morphological marker, disease resi-
stance is dominant and, therefore, the genotypic
classes of heterozygous and homozygous for the re-
Genetic Linkage Mapping
sistantparent(parentA)cannotbedistinguished(re-
The high-density genetic linkage maps facilitate sistant plants can have allelic compositions of ‘‘RR’’
map-based cloning experiments, quantitative trait or‘‘Rr,’’andsusceptibleplantshave‘‘rr’’).Inspection
AB
nt nt F progeny
ee 2
arar 1
PPF 1 2 3 4 5 6 7 8 9 10 11121314151617181920
Marker A
1 2 3 4 5 6 7 8 9 10 11121314151617181920
Marker B
1 2 3 4 5 6 7 8 9 10 11121314151617181920
Disease
resistance (R) R S R R R S R R R R R S R S R R R R S R R R R
gene
Phenotype: R=resistant; S=susceptible
Genotypes: Parent A=RR; Parent B=rr; F =Rr; F progeny R=RR or Rr;
1 2
Linkage map
B R gene A
5 10
Figure3 GenotypicdataoftwoDNAmarkers(AandB)andphenotypicdataofonemorphologicalmarker(diseaseresistancegene
‘‘R’’)fortwoparents,theF plantderivedfromcrossingthetwoparents,and20F individuals.TheDNAmarkersareco-dominant;thus,
1 2
allpossiblegenotypescanbedistinguished(homozygousforparentA,heterozygous,andhomozygousforparentB).Themorphological
marker‘‘R’’isdominantandthereforethegenotypesofresistantF individualscannotbedistinguished(resistantplantscanbeeither
2
homozygousforparentA(RR)orheterozygous(rr)).Theresultinggeneticlinkagemapofthethreelociandgeneticdistancesseparating
themisshownatthebottom.