Virus-Resistant Transgenic Horticultural Crops: Safety Issues and Lessons from Risk Assessment Studies - Transgenic Horticultural Crops: Challenges and Opportunities - page 278

OVERVIEW OF RISK LESSONS OF TRANSGENIC
HORTICULTURAL CROPS
Based.on.the.existing.body.of.research.into.the.potential.risks.posed.by.virus-resistant.
genetically.modiied.horticultural.crops,.there.appears.to.be.a.signiicant.amount.of.
evidence.that.these.crops.have.little.to.no.detrimental.impact.on.the.environment.and.
human.health.beyond.those.of.conventional.horticultural.crops.
The.work.on.summer.squash.supports.the.aforementioned.claim.that.transencap-
sidation.is.not.a.signiicant.environmental.risk.beyond.that.already.posed.by.multiple.
infected. conventionally. bred. plants. 4,87 . This. is. also. true. for. the. risks. of. gene. low.
to.free-living.relatives 84-86 .and.human.health.effects,.speciically.on.allergenicity. 46 .
Furthermore,.there.is.a.documented.safe.release.of.this.transgenic.crop.over.the.past.
12.years.in.the.United.States. 2
In. the. case. of. papaya,. the. results. from. the. allergenicity. and. nutritional. experi-
ments. seem. to. very. strongly. refute. risks. to. human. health. 73,93,102,111 . The. threat. of.
negative.nontarget.effects.appears.to.be.lessened.though.the.papers.published.on.this.
topic.are.very.limited.in.scope. 105-107 .With.respect.to.the.other.areas.of.risk,.direct.
experimental.evidence.does.not.appear.to.exist.in.suficient.quantities.to.make.any.
irm.conclusions.on.transencapsidation,.recombination,.and.gene.low..However,.the.
safe. commercial. use. of. transgenic. papaya. over. a. decade. and. evidence. from. other.
transgenic.crops.may.speak.to.some.of.these.issues.enough.to.be.extrapolated.to.the.
PRSV.papaya.case. 2
The.work.on.plums.supports.the.fact.that.recombination.is.unlikely.to.facilitate.
the.emergence.of.virus.species.with.altered.or.new.biological.properties.beyond.the.
occurrence. in. conventional. plums. subjected. to. mixed. virus. infection. 121 . This. also.
applies. to. the. risks. on. nontarget. organisms. 121 . It. is. doubtful. that. transencapsida-
tion.could.occur.to.a.meaningful.level.in.transgenic.plum.line.C5,.because.of.unde-
tectable.levels.of.PPV.coat.protein. 115-117 .This.also.casts.doubt.on.whether.the.coat.
protein.is.expressed.at.a.meaningful.level.to.have.human.health.impacts.differing.
signiicantly.from.those.seen.in.PPV-infected.non-transgenic.plums.
Based.on.the.information.from.the.transgenic.tomato.and.sweet.pepper,.there.is.
further.evidence.to.support.the.claim.that.gene.low.is.not.a.major.concern.in.this.
case. 109 . Most. signiicantly,. the. animal. feeding. studies. give. further. support. to. the.
safety.of.virus-resistant.transgenic.crops.expressing.viral.coat.protein.genes. 108,111
Similar.conclusions.on.the.risk.assessment.of.other.transgenic.horticultural.crops.
have. been. reported.. The. only. Bt . horticultural. crop. commercially. available. in. the.
United.Stated.is. Bt .sweet.corn,.although.other. Bt .transgenic.vegetables.(i.e.,.cauli-
lower,.cabbage,.and.eggplant).are.being.considered.for.commercialization.in.India. 62 .
Studies. have. shown. that. Bt . sweet. corn. provides. consistently. excellent. control. of.
lepidopteran. pests.. This. technology. also. substantially. reduces. insecticide. applica-
tions.and.better.preserves.predators.of.the.European.corn.borer.than.commonly.used.
broad-spectrum. insecticides. 62 . Bt . sweet. corn,. like. virus-resistant. summer. squash.
and.papaya,.are.consumed.in.the.United.States.with.no.ill.effects.reported.
In.summary,.transgenic.horticultural.crops.have.become.important.components.
of. disease. and. pest. management. programs. in. the. United. States. and. the. People's.
Republic.of.China..Their.adoption.rate.is.constantly.increasing.since.their.irst.release.