Transgenic Ornamental Crops - Transgenic Horticultural Crops: Challenges and Opportunities - page 73

is. phenotypically. manifested. as. a. dwarf. habit,. increased. rooting,. darker. leaves,.
increased.lateral.shoots,.and.increased.lowering.(reviewed.by.Casanova.et.al. 122 )..The.
rol .genes.have.been.transformed.into. Antirrhinum , 123 . Begonia , 124 . Rosa , 125 . Petunia , 126 .
Dianthus , 127 . Osteospermum , 128 . Angelonia , 129 . Lilium , 130 .and. Pelargonium . 131 .In.some.
instances,.transgenic.plants.had.smaller.lowers.and.reduced.fertility,.which.could.be.
a.limitation.from.a.production.standpoint,.but.may.be.useful.in.addressing.environ-
mental.concerns.since.transgene.low.would.likely.be.more.restricted.
BIOTIC STRESS TOLERANCE
Engineering.plants.to.tolerate.biotic.stresses.has.the.potential.for.large.cost.savings.
in. pesticide. chemicals. leading. to. more. environmentally. friendly. production. prac-
tices.(reviewed.by.Redenbaugh.and.McHughen 132 )..Pesticide.use.data.collected.from.
farmers.growing.insect.resistant.transgenic.corn.and.cotton.indicate.biotech.crops.
have.decreased.pesticide.usage,.increased.yield,.higher.quality.crops,.and.decreased.
labor. 133 . These. are. clear. beneits. that. are. currently. only. realized. by. producers. of.
biotech.food.crops,.but.are.applicable.to.ornamental.crops..While.there.are.no.com-
mercially.available.biotech.ornamentals.engineered.for.biotic.stress.tolerance,.this.
trait. is. being. engineered. in. some. ornamentals. and. a. few. examples. will. be. high-
lighted.here.
There.are.a.number.of.strategies.for.genetic.engineering.plants.to.be.more.resis-
tant.to.insect.attack..Engineering.plants.to.produce.insect.toxins.has.been.the.most.
successful. means. to. date.and. is.widely. used. today. in. corn.and.cotton. production..
Genes. encoding. insect. control. proteins. from. Bacillus thuringiensis ,. know. as. Cry .
genes,.have.been.cloned.and.modiied.for.eficient.production.in.plants 134 .(reviewed.
by.Schuler.et.al. 135 )..These.proteins.bind.to.gut.receptors.in.lepidopteran,.dipteran,.
and.coleopteran.insects.causing.disfunction.of.the.insect.gut.and.lysis.of.gut.epithe-
lial.cells.leading.to. insect.death.(reviewed.by.Gill.et.al. 136 )..The. Bacillus cryIA(b) .
gene. has. been. introduced. into. chrysanthemum. causing. feeding. insects. to. die. and.
signiicantly. less. consumption. of. leaf. area. 137 . Insects. feeding. on. transgenic. plants.
consumed. less. than. 5%. of. the. leaf. area. while. 95%. or. more. of. control. leaf. area.
was.consumed..Similarly,.transgenic.petunias.expressing.the. cryIA(c) .gene.caused.
signiicant.reduction.in.insect.fecundity. 138 .While.the.BT.toxins.have. proven.to.be.
very. successful. for. insect. management,. other. biotech. insecticidal. strategies. have.
been.developed.and.will.be.important.considerations.for.crop.management.to.avoid.
insect.resistance.issues..As.discussed.in.“Plant.Volatiles”.section,.plants.can.be.engi-
neered.to.produce.volatiles.that.modify.insect.behavior.or.attract.predatory.insects..
Protease.inhibitors,.α-amylase.inhibitors,.lectins,.and.nonvolatile.secondary.metab-
olites,.such.as.tryptamine,.are.also.means.for.engineering.insect.defense.in.plants.
(reviewed. by. Llewellyn. and. Higgins 139 ).. However,. examples. of. these. methods. for.
engineering.insect.defense.in.ornamental.plants.are.few.
While.disease.resistance.in.ornamental.crops.has.largely.been.achieved.through.
traditional. breeding,. this. trait. has. been. successfully. genetically. engineered. using.
a. number. of. approaches.. Transgenic. expression. of. genes. commonly. induced. by.
disease. infection. (pathogenesis-related. genes,. PR). confers. enhanced. disease. resis-
tance.. For. example,. chitinases. degrade. fungal. cell. walls. into. breakdown. products.