Agriculture Reference
In-Depth Information
over.95%.of.the.total.Hawaiian.papaya.production..In.1992,.PRSV.was.discovered.
in.Hawaii's.Puna.district 5 .and.within.3.years.nearly.all.of.the.plants.in.Puna.were.
severely.affected..By.1997,.papaya.production.had.declined.by.36%.from.21,800.tons.
(at.the.start.of.the.outbreak).down.to.14,000.tons. 6
Transgenic. papaya. cultivars,. 'SunUp'. and. 'Rainbow,'. resistant. to. PRSV. were.
released.in.1998.and.widely.planted.in.Hawaii.providing.effective.virus.control.and.
allowing.for.increased.papaya.production.(from.the.low.in.1998). 2,6 .Since.the.release.
of.the.PRSV-resistant.transgenic.papaya.in.Hawaii,.additional.papaya.cultivars.resis-
tant.to.PRSV.containing.other.PRSV.coat.protein.transgenes.have.also.been.devel-
oped.in.Australia,.Florida,.Brazil,.Taiwan,.Jamaica,.the.Philippines,.Thailand,.and.
Venezuela. 68,81,89-94 . The. transgenic.varieties. are.at.various.stages.of. development.
and. evaluation.. Other. transgenic. papaya. purportedly. resistant. to. PRSV. have. also.
been.developed.utilizing.the.viral.replicase.gene 67 .but.the.major.focus.here.will.be.
on.PRSV-resistant.papaya.involving.the.coat.protein.gene.
Risk Studies
Since.the.development.and.commercial.release.of.transgenic.papaya.expressing.the.
coat.protein.gene.of.PRSV,.numerous.experiments.and.ield.trials.have.probed.the.
potential.risks.associated.with.this.transgenic.technology.
As.one.of.the.irst.widely.commercialized.fruit.crops,.there.has.been.much.inter-
est.in.the.effects.of.the.coat.protein.transgene.on.human.health.and.potential.aller-
genicity.as.well.as.investigations.into.compositional.changes.in.fruit.with.respect.to.
nutrient. and. antinutrient. content.. Descriptions. of. transgenic. papayas. developed. in.
Hawaii.report.on.percent.soluble.solids.above.the.minimum.required.for.commercial.
fruit.and.yields.of.almost.three.times.those.of.industry.averages. 5 .Comparable.values.
for.vitamin.C.and.minerals.(potassium,.phosphorus,.calcium,.magnesium,.sodium,.
iron,.copper,.zinc,.and.boron).for.the.transgenic.and.non-transgenic.cultivars.have.
been.published. 95,96 .Also,.no.evidence.of.ill.effects.has.been.linked.to.the.consump-
tion.of.transgenic.papaya.in.the.United.States.and.Canada. 2
Another.study.on.transgenic.papaya.from.Thailand.reported.on.comparable.nutri-
ent.composition.with.the.non-transgenic.counterpart. 93 .Recently,.the.levels.of.nutrients.
(protein,.fat,.carbohydrate,.minerals).and.antinutrients.(oxalates,.hydrocyanic.acid,.
and.benzyl.isothiocyanate).in.three.transgenic.papaya.lines.expressing.a.PRSV.coat.
protein.gene.construct,.which.are.not.currently.available.on.the.market,.were.com-
pared.to.those.of.the.commercial.papaya.cultivar.'Sunrise.solo'.grown.under.the.same.
conditions.in.an.experimental.plot.in.Jamaica. 73 .Since.papaya.is.a.climacteric.fruit,.
three.stages.of.maturity.were.considered.to.facilitate.an.evaluation.of.the.changes.
in.various.parameters.that.accompany.the.ripening.process.after.harvest..With.the.
exception.of.one.transgenic.line,.no.signiicant.differences.were.observed.in.selected.
nutrients. and. antinutrients. between. the.control. and. test. samples.at. three.stages.of.
maturity,. although. a. few. random. variations. were. noted. 73 . Overall,. the. composi-
tional.changes.over.the.three.maturities.were.as.expected.and.comparable.to.those.
reported. 97-99 .Sugars,.vitamin.C,.and.carotenoids.followed.a.general.upward.trend,.
whereas.slight.decreases.in.moisture,.ash,.and.fat.at.the.inal.stage.of.ripening.were.
observed.. Some. variability. in. the. concentrations. of. the. three. antinutrients. tested.
was.observed,.but.the.values.were.within.the.range.of.concentrations.reported.for.
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