Agriculture Reference
In-Depth Information
Production. of. ornamental. crops. is. a. global. industry,. having. a. multibillion. dollar.
value. worldwide. driving. the. development. and. introduction. of. novel. ornamental.
plants.solely.for.human.use.
Novel.ornamental.plants.have.been.developed.by.traditional.breeding.techniques,.
including. hybridization. and. mutation. breeding,. and. more. recently. by. introducing.
precise,.direct.genetic.changes.through.genetic.engineering..There.are.major.poten-
tial. beneits. to. genetic. engineering. including. the. opportunity. for. the. introduction.
of. genes. and. traits. not. present. in. the. natural. gene. pool. of. the. species. of. interest.
without.altering.the.genetic.background..A.variety.of.consumer.and.producer.traits.
have.been.successfully.modiied.in.ornamental.plants.through.genetic.engineering,.
including. lower. color,. fragrance,. plant. architecture,. cut. lower. vase. life,. disease.
resistance,.abiotic.stress,.and.herbicide.tolerance. 2,3 .This.chapter.provides.an.over-
view. of. the. traits. modiied. by. transgenic. technology,. examines. the. beneits,. and.
discusses.issues.that.have.limited.the.commercialization.of.transgenic.ornamental.
crops.over.the.past.decade.
FLOWER COLOR
Flower.color.and.color.pattern.are.key.elements.in.consumer.selection.of.lowering.
ornamentals.. It. has. been. of. considerable. interest. to. develop. commercial. series. of.
plants.with.a.full.spectrum.of.lower.colors..Producing.a.series.of.plants.having.low-
ers.with.the.full.color.palette.through. traditional.breeding.is.challenging.for.most.
species.since.the.genetics.required.for.producing.all.the.color.compounds.is.usually.
limiting.. Through. identiication. and. introduction. of. color. producing. enzymes. and.
pathways.from.other.plants,.new.colors.can.be.introduced.into.varieties.that.would.
otherwise.be.dificult.to.obtain.(Table.3.1).
Flavonoids,. carotenoids,. chlorophyll,. and. betalins. are. the. primary. classes. of. com-
pounds.that.give.lowers.their.characteristic.color..Flavonoids.are.widely.distributed.in.
many.plant.families,.conferring.shades.of.red,.orange,.yellow,.blue,.and.violet..Carotenoids.
are. derived. from. isoprenoids. and. give. rise. to. orange. and. yellow. shades,. marigolds.
being. the. classic. example.. Betalins. are. water-soluble. nitrogen-containing. com-
pounds.derived.from.tyrosine.and.are.taxonomically.restricted.to.the.Caryophyllales. 4 .
Biosynthesis.of.these.compounds.has.been.well.characterized.in.many.plant.species.and.
readers.are.referred.to.published.reviews.elsewhere.for.detailed.information.about.their.
biosynthesis. 4,5
f lavonoIdS
Chalcones,.aurones,.anthocyanins,.lavones,.and.lavonols.are.the.major.groups.of.
lavonoids.that.impart.the.colorful.loral.display.seen.in.the.angiosperms..Novel.and.
complex.coloration.patterns.have.been.achieved.primarily.by.manipulation.of.the.la-
vonoid.biosynthetic.pathway.including.preventing.or.redirecting.lavonoid.synthesis.
through. gene. silencing,. introducing. biosynthetic. enzymes. with. different. substrate.
preferences.or.novel.activities,.and.modifying.expression.of.regulatory.transcription.
factors.controlling.lavonoid.biosynthetic.genes.(Table.3.1).
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