Agriculture Reference
In-Depth Information
Given.the.tremendous.amount.of.transgenes.that.have.been.engineered.to.provide.
virus.resistance.and.the.numerous.crops.that.these.genes.have.been.introduced.into,.
there.is.a.staggering.amount.of.scientiic.literature.on.resistance.to.viruses.in.trans-
genic.crop.plants.
17
To.focus.our.efforts.on.indings.that.we.believe.to.be.the.most.relevant,.we.have.
chosen.to.examine.risk.assessment.of.virus-resistant.transgenic.horticultural.crops.
already. commercialized. (e.g.,. papaya,. summer. squash,. tomato,. and. sweet. pepper).
or.awaiting.deregulation.(e.g.,.plum)..In.our.examinations,.we.will.rely.primarily.on.
realistic.ield.studies,.which.may.provide.the.most.accurate.relection.of.risks,.and.to.
a.lesser.extent.on.laboratory.and.greenhouse.studies..We.will.look.at.the.conclusions.
that.can.be.made.about.the.safety.of.virus-resistant.transgenic.horticultural.crops.by.
analyzing.the.signiicance.of.risk.assessment.studies,.as.well.as.at.identifying.gaps.in.
knowledge.where.further.experimental.evidence.may.be.needed.before.conclusions.
can.be.drawn.with.respect.to.the.safety.of.these.crops.
S
QuaSh
r
eSIStant
to
c
ucumber
m
osAic
V
irus
,
z
ucchini
Y
ellow
m
osAic
V
irus
,
and
w
Atermelon
m
osAic
V
irus
Background
The.irst.disease-resistant.transgenic.crop.to.be.commercialized.in.the.United.States.
was.transgenic.summer.squash..This.squash,.which.possesses.resistance.to.ZYMV.
and.WMV,.was.deregulated.in.1994.
2,3
.Another.summer.squash.cultivar.resistant.to.
CMV,.ZYMV,.and.WMV.was.later.released.in.1996.
2-4
.Virus-resistant.transgenic.
squash.possess.the.coat.protein.genes.from.each.virus..Early.testing.indicated.that.
they. provide. high. resistance. to. viral. infection
1,3,4
. and. prevent. viral. epidemics. by.
reducing.secondary.plant-to-plant.spread.
83
.No.similar.resistance.to.multiple.viruses.
is.available.in.traditionally.bred.commercial.summer.squash.
2
Squash. is. unique. among. commercial. transgenic. plants. in. that. it. is. monoecious.
and. readily. outcrosses,
44
. emphasizing. the. signiicance. of. gene. low. issues. for. this.
crop..Since.the.center.of.origin.for.many.squash.species.is.in.the.southern.United.
States. and. Mexico,
42
. the. commercialization. of. virus-resistant. transgenic. squash.
marks.the.irst.transgenic.crop.to.be.released.within.its.center.of.origin.
Risk Studies
As.summer.squash.was.the.irst.virus-resistant.crop.with.a.coat.protein.transgene.to.
be. commercialized,. the. potential. allergenicity.and. impacts. on. human. health. were.
considered.extensively.
46
.No.signiicant.difference.in.protein,.total.fat,.dietary.iber,.
carbohydrate,. calories,. vitamins.A.(and.its.precursor,. β-carotene). and. C,. calcium,.
iron,.sodium,.ash,.moisture,.and.sugar.proiles.(fructose,.glucose,.sucrose,.maltose,.and.
lactose).was.found.between.transgenic.and.non-transgenic.squash.
46
.Also,.an.exami-
nation. into. human. consumption. of. virus-infected. non-transgenic. summer. squash.
fruits.led.to.the.conclusion.that.there.was.likely.to.be.no.signiicant.negative.impact.
on.human.health.beyond.those.of.virus-infected.traditionally.bred.squash.cultivars.
with.which.consumers.have.a.long.history.of.exposure.to.without.any.clear.hazards.
arising.
46
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