Agriculture Reference
In-Depth Information
Examination.of.Risks.Associated.with.Transgenic.Plum.Which.
Is under Consideration.for.Deregulation................................................................ 276
Background........................................................................................................ 276
Risk.Studies....................................................................................................... 277
Overview.of.Risk.Lessons.of.Transgenic.Horticultural.Crops............................... 278
Perspectives............................................................................................................ 279
Introduction........................................................................................................ 279
Future.Trends..................................................................................................... 280
Conclusions............................................................................................................ 281
References.............................................................................................................. 281
INTRODUCTION
Horticultural.crops.were.the.irst.transgenic.crops.commercialized.in.the.United.States.
in. the. mid-1990s.. Among. the. irst. of. these. were. virus-resistant. transgenic. summer.
squash.(
Cucurbita pepo
.ssp..
ovifera
.var..
ovifera
.L.)..The.irst.transgenic.squash.cul-
tivars,.deregulated.in.1994,.were.resistant.to.
Zucchini yellow mosaic virus
.(ZYMV).
and.
Watermelon mosaic virus
.(WMV).
1-3
.Other.transgenic.summer.squash.cultivars.
resistant. to. ZYMV,. WMV,. and.
Cucumber mosaic virus
. (CMV). were. released. in.
1996
2-4
. followed. by. papaya. (
Carica papaya
. L.). genetically. modiied. for. resistance.
to.
Papaya ringspot virus
.(PRSV).in.1998.
2,5,6
.To.date,.virus-resistant.summer.squash.
and.papaya.are.the.only.transgenic.horticultural.crops.that.are.commercially.released.
in. the. United. States,. along. with.
Bt
. sweet. corn. (
Zea mays
. L.).
7
. Potato. (
Solanum
tuberosum
.L.).resistant.to.
Potato virus Y
.(PVY),.
Potato leafroll virus
.(PLRV).and.the.
Colorado.potato.beetle.were.released.in.1998,.but.were.withdrawn.from.the.market.
almost.immediately.thereafter.due.to.anti-biotechnology.campaigns.and.international.
trade. barriers.
8
. In. the. People's. Republic. of. China,. transgenic. tomato. (
Solanum
esculentum
.L.).and.sweet.pepper.(
Capsicum annuum
.L.).resistant.to.CMV.and.papaya.
resistant.to.PRSV.have.also.been.released.
9
The. virus-resistant. transgenic. horticultural. crops. commercially. available. have.
been.developed.by.applying.the.concept.of.pathogen-derived.resistance.
10
.Pathogen-
derived.resistance.refers.to.the.use.of.a.pathogen's.own.genes.to.confer.resistance.in.
a.host.to.that.pathogen..In.the.case.of.the.horticultural.crops.released.to.date.in.the.
United.States,.engineered.virus.resistance.has.been.achieved.through.expression.of.
viral.coat.protein.genes.
3,6
The.development.and.release.of.transgenic.horticultural.crops,.in.particular.those.
engineered. for. virus. resistance,. have. raised. potential. safety. issues. regarding. their.
impact. on. the. environment. and. human. health.
2,11-13
. Similarly,. concerns. have. been.
expressed.over.the.release.of.horticultural.crops.expressing.
cry
.toxin.genes.from.the.
bacterium,.
Bacillus thuringiensis
. (Bt).
14,15
. Over. the. years,. a. signiicant. amount. of.
research.has.been.done.to.address.safety.issues.and.examine.potential.risks..In.this.
chapter,.we.provide.a.synopsis.of.transgenic.horticultural.crops,.in.particular.virus-
resistant.transgenic.crops.with.the.major.emphasis.on.those.that.are.currently.available.
in. commerce.. We. also. examine.the. mechanisms. underlying. engineered. virus. resis-
tance.and.discuss.potential.safety.issues.with.this.technology..We.then.examine.risk.
assessment. research. by. focusing.on.commercial.crops.for.which.data. from.realistic.
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