Genetic Engineering of Grapevine and Progress toward Commercial Deployment - Transgenic Horticultural Crops: Challenges and Opportunities - page 323

become.invasive.pests..Because.transgenes.are.dispersed.from.genetically.engineered.
vines. by. pollination.and/or.seed.production,.certain.aspects. of.grape. reproductive.
biology.should.be.evaluated..Molecular.methods.using.marker.genes.for.detection.of.
transgenes.and.transproteins.in.grape.seed/fruit.tissues.to.monitor.movement.of.such.
genes.through.sexually.produced.progeny.are.readily.available..In.addition.to.gene.
movement,. the. relative. vigor. and. adaptation,. including. survivability. of. transgenic.
progeny,.must.be.determined.to.assess.their.potential.to.become.invasive.pests.
Gene Flow via Pollen
In.varieties.with.perfect.lowers,.the.calyptrate.lower.structure.and.arrangement.of.many.
lowers.on.a.panicle.favor.self-pollination. 37 .The.extent.to.which.natural.cross-pollination.
occurs. in. grape. is. controversial.. Natural. hybridization. among. native. species. has. been.
detected. 39 .Grape.has.been.considered.to.be.wind-pollinated,.with.pollen.low.occurring.
no.further.than.20.ft..from.the.source. 40 .However,.cross-pollination.has.been.suggested.to.
be.enhanced.by.insect.pollinators.in.certain.instances..For.example,.in.muscadine.grape.
vineyards.composed.of.female.(self-sterile).vines.that.require.pollinator.vines,.fruit.set.has.
been.enhanced.by.incorporation.of.honeybee.hives.(reviewed.by.McGregor 41 )..However,.
in.a.controlled.study,.vines.isolated.from.wind-blown.pollen.by.cages.did.not.produce.
appreciatively.more.fruit.when.bee.hives.were.added. 42 .Airborne.pollen.yields.have.been.
accurately.measured.in.order.to.predict.seasonal.fruit.yield. 43,44 .The.latter.studies.described.
airborne.pollen.loads,.but.did.not.address.hybridization/gene.low..Thus,.the.maximum.
distance.that.viable.pollen.moves.from.one.grapevine.to.another.and/or.the.frequency.of.
hybridization.resulting.from.such.movement.have.not.been.adequately.documented..This.
issue.has.taken.on.new.importance.with.the.advent.of.genetically.GE.grapevine.
Gene Flow via Seed
The.possibility.for.gene.low.via.seed.dispersal.from.transgenic.vines.would.be.low.
if.seeds.result.from.selfs,.as.mentioned.above,.and.because.grape.has.a.high.level.of.
inbreeding.depression. 45 .Therefore,.the.resulting.selfed.plants.lack.vigor.and.tend.not.
to.survive..For.example,.of.plants.grown.from.over.one.thousand.selfed.seeds,.none.
were.able.to.survive.to.lowering.when.planted.in.a.research.vineyard.at.Leesburg,.
Florida.(Gray,.personal.observation)..Further,.when.seedless.varieties.are.used,.there.
is. no. opportunity. for. seed. dispersal.. Thus,. frequency. of. natural. self. versus. cross-
fertilization.should.be.investigated.
p otentIal I mpactS of t ranSGene f low In G rapevIne
Potential for Transgene Pollen Flow into Non-GE Vineyards
Transgene. movement. into. non-GE. vineyards. as. a. consequence. of. pollen. low.
should. have. minimal. impact.. This. is. because. only. the. embryo. and. endosperm,.
which.are.encased.in.a.non-transgenic.hard,.durable.seed.coat,.can.become.trans-
formed. by. pollen. from. a. transgenic. vine.. Our. current. research. using. the. GFP.
marker.system.conirms.this..Grape.seed.is.discarded.whether.fruit.is.used.fresh.
or. for. processed. products,. with. the. exception. of. use. for. oil. extraction. 46 . Thus,.
if. seed. is. properly. disposed,. there. is. little-to-no. risk. of. transgene. movement..