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Risk Assessment of Pollen-Mediated GeneFlow in Transgenic Cotton Containing

cry1Ac and cry2Ab2 Genes in ConfinedField Trial at KARI-Mwea, Kenya

Mbogori M.N1. Mutisya J.M1., Waturu C.N2., Wessels

W3., Wanjala B.W1., Orende J4., and Njinju S.M5

1 KARI, Biotechnology2 KARI-Thika3 Monsanto, Nairobi4 Dept of Plant Science and Crop Protection,

College of Agriculture and Veterinary Sciences

5 KARI-Mwea

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INTRODUCTION-WHAT IS GENE FLOW?

Definition= In population genetics, gene flow(also known as gene migration) is the transfer

ofalleles of genes from one population toanother (between interbreeding populations)

Transfer of gene(s)fromtransgenictonon-transgenic and wild relatives

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Pathways of gene flow

1. Pollen-mediated Gene Flow (PGF)1. SpatialProximity2. TemporalProximity

3. Floral Compatibility

4. Mating Compatibility and Fertility2. Seed/Propagule-mediated Gene Flow

1. Mobility

2. propagulepressure;3. Dormancy

3. Horizontal Gene Transfer -\Transfer fromviruses/bacteria toplants/animals andviceversa

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Genescarriedbypollencanflow intwodirections,from atransgeniccroptosimilar conventionalcrops,other GMO

crops andto wild relatives, andfromconventional and GMOcrops and wild relativesto a GMOcrop. Theimplicationsof

geneflow inbothdirections aresimilar ifnot alwaysidentical(Chvre,et al., 2000; Lu, B.-R., 2003).

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Introduction-Pollen-mediated Gene Flow

Influencing factors1. SpatialProximity

The GMcrop anditssexually-compatible relativesoccur withintheir respectivepollinationdistances

2. TemporalProximitythe GMcrop andthe relativehaveoverlapping floweringperiods,to allow theviablematerialtobe released andreceived, andfertilizationtooccur

3. Floral Compatibility

pollenvectorsthatvisit andtransfer polleneffectivelybetweenbothdonor and recipientplants arepresent

4. Mating Compatibility and FertilitySelfing vs.outcrossing influencescharacteristicssuch as

pollenproduction andlikelihoodof receiving pollenfrom

another population

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Introduction-Cotton(Gossypium hirsutum )

1. Grown in warmregions aroundthe world2. Originofthe genusGossypium isnotknown,

butthe genus' primarycentresofdiversity

areMexico, Africa, Arabia, and Australia3. Cotton is a perennialplantthat isplanted

and harvested annually

4. Cultivatedcotton Diploid- 2setschromosomes(Gossypium

herbaceum L., Gossypium arboreum L.)

Tetraploid- 4setschomosomes(Gossypium

hirsutum L. and Gossypiumbarbadense L.)

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Risk assessment for GMO

Everycrophas a different relationshiptotheenvironment, whichmeansenvironmentalimpact assessmentsmustbeconductedon a

case-by-casebasis.

Differentcropsposedifferentthreats

whenitcomestoout-crossing or escapingcultivation.

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Is out-crossing of transgenes fromcotton possible?

Cottonispredominantlyself-pollinating Pollencanbetransferredbyinsects(bees)

Out-crossing ratesof upto 28 percent withother

cottoncultivarsin adjacentplotshavebeenobserved under fieldconditions,declining rapidlywithdistance

Crossing plants withdifferentploidylevels rarely

resultsinfertilehybrids

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Objectives & scope of work

1. Establishif Bollgard I & II arecompatiblewithHART89M

2. Determineifnaturalpollinationoccurs

3. Determinenaturalpollinationdistances

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Materials used

Genotype Trait Source

DP5415 Isoline Monsanto

DP4049 Isoline Monsanto

DP448B (Ballgard@) C ry1Ac Monsanto

DP404BG(Ballgard@) C ry1Ac Monsanto

HART 89 M Localcultvated Kari-Mweacry1Accry 2Ab2

Monsanto

cry1Accry2Ab2

Monsanto

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Materials andMethods-fieldlayout

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Materials andMethods-Testing for bt-protein

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Reading Strips

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Summeryfor 3 season: N-North,E-East,W-West,S-South

Row Season 1

- 2006

Season 2 - 2007 Season 3 - 2008

E N S W E S W E

1 3 0 0 2 0 0 0 62 1 0 0 2 0 0 0 0

3

1 1

0

1

0 0 0 0

4 1 0 0 0 0 0 0 0

5 0 0 0 0 0 0 0 0

6 0 1 1 0 0 0 6 07 1 0 0 0 0 0 0 0

8 0 0 1 0 0 0 0 0

9 0 0 0 0 0 0 0 0

10 0 0 0 0 0 0 0 0

11 0 0 0 0 0 0 0 0

12 0 0 0 0 0 0 0 0

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Summeryof results1. Bollgard II & I arecompatibleHART89M

Positivefor allmanuallycrossed

1. Naturalpollinationoccurred Seasonone-7positiveplantsfor btprotein

Seasontwo-9 positiveplantsfor btprotein

Seasonthree-12 positiveplantsfor btprotein

2. Naturalpollinationoccurred upto a distance

of 8 meters Seasonone-7meters

Seasontwo-8 meters

Seasonthree-6 meters

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Conclusion

1. Occurrence of gene flow between Bt-cotton and

non- Bt-cotton mediated by pollen was observed2. However, dispersal of cotton pollen was negligible

above 8 meters from the source plant. This could be

attributed to the fact that cotton is mainly a self

pollinating plant

3. Based on these results, an isolation distance of at

least 10 meters is therefore necessary for purposes

of sanitizing the crop or in seed production.

Alternatively, Bt-cotton plants could be surrounded

by about 10 meter band of non-transgenic cotton asa strategy to minimize unintended gene flow.

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