Agriculture Reference
In-Depth Information
for. growers,. producers,. and. handlers,. because. they. are. focused. on. sustaining.
yields. and. productivity.. Disease. and. pest. resistance. are. examples. of. important.
input.traits..Output.traits,.which.preserve.the.quality.and.nutritional.value.of.the.
fruit,.are.of.primary.importance.to.the.consumer,.though.they.ultimately.beneit.
the.grower.as.well..Increasingly,.fruit.consumption.has.been.linked.with.improved.
nutrition.and.disease.prevention,.and.thus.USDA.guidelines.suggest.that.fruit.and.
nuts.are.an.important.component.of.the.daily.diet..Many.fruit.quality.traits,.like.
lavor,.are.important.for.consumption,.as.a.good.lavor.makes.the.fruit.more.desir-
able..Fruit.quality.is.also.important.for.downstream.products.like.fruit.juice.and.
wine..In.this.chapter,.we.outline.the.progress.that.has.been.made.in.different.fruit.
crops.to.manipulate.both.input.and.output.traits.
GENETIC TRANSFORMATION OF FRUIT AND NUT TREE CROPS
I
mportance
of
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enetIc
e
nGIneerInG
A. major. breeding. objective. is. to. combine. fruit. quality. with. other. horticulturally.
important.traits.such.as.plant.architecture,.adaptation.to.extreme.environmental.con-
ditions,.and.decreasing.the.amount.of.chemical.input.required.to.control.pests.and.
diseases..The.production.of.new.varieties.by.conventional.breeding.is.a.complex.and.
time-consuming.process,.especially.for.fruit.trees,.due.to.the.high.level.of.heterozy-
gosity,.pronounced.inbreeding.depression,.long.juvenile.phase,.and.complex.repro-
ductive.biology..The.plant.breeder.must.wait.many.years.to.be.able.to.evaluate.fruit.
quality,.and,.because.fruit.trees.are.large.perennial.plants,.a.relatively.small.number.
of.seedling.progeny.can.be.evaluated.
3,4
.In.addition,.the.characters.that.constitute.a.
good.cultivar.in.most.instances.are.polygenic.in.their.inheritance;.thus,.the.probability.
of.recombining.sets.of.genes.that.determine.the.essential.properties.of.a.given.cultivar.
is.low.
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.In.wine.grape.breeding,.legal.and.economic.hurdles.can.be.even.larger.than.
the.biological.obstacles.described.above..New.wine.grape.varieties.are.not.welcome.
because.the.wine.industry.relies.predominantly.on.a.few.select.and.ancient.cultivars;.
also,. vintners. are. constrained. by. tradition,. regulation,. and. economics,. so. they. use.
classical.varieties,.such.as,.'Cabernet.Sauvignon',.'Merlot',.and.'Chardonnay'.
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Direct.genetic.modiication.by.the.introduction.of.single.genes.offers.the.opportu-
nity.to.direct.very.speciic.changes.in.existing.cultivars,.to.increase.resistance.to.abi-
otic.stress,.diseases,.and.pests.and.to.modify.fruit.composition.in.very.precise.ways..
Vegetative.propagation.means.that.modiications.to.traditional.cultivars.by.genetic.
transformation.leave.the.essential.characters.and.identity.of.the.cultivars.unaltered,.
a.result.that.would.be.very.dificult.to.achieve.by.conventional.breeding.where.two.
genomes.are.intermingled.
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.Last.but.not.least,.genetic.transformation.also.offers.the.
opportunity.to.study.how.genes.control.the.growth.and.development.of.plants.
c
urrent
S
tatuS
of
G
enetIc
t
ranSformatIon
of
p
erennIal
c
ropS
A. wide. variety. of. transformation. and. regeneration. protocols. have. been. used. to.
produce.transgenic.fruit.trees..However,.in.most.species,.transformation.and.regen-
eration. of. commercial. cultivars. are. not. routine,. generally. being. limited. to. a. few.
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