Artificial hybridization class 12 project

About the artificial hybridization and it's process

1. HYBRIDIZATION
Hybridization-producingnewcropvarieties-crossingtwo
ormoreplantsofunlikegeneticconstitution.
Basedonthenature&relationshipofplantstobecrossed,
hybridizationcanbe–
Inter-varietal–Crossbet.plantsoftwodiff.var.ofsame
species-intra-specifichybridization.Eg.HybridMaize.
Intra-varietal–Crossbet.twoplantsofdiff.genotypesbut
samevariety.
Inter-specific–Crossbet.twospeciesofgenus-Eg.Wheat,
Cotton,Tobacco.
Inter-generic–Crossbet.twodiff.genera.
Eg.SugarcaneXBamboo,WheatXRye,RadishXCabbage.
Hybridization-producingnewcropvarieties-crossingtwo
ormoreplantsofunlikegeneticconstitution.
Basedonthenature&relationshipofplantstobecrossed,
hybridizationcanbe–
Inter-varietal–Crossbet.plantsoftwodiff.var.ofsame
species-intra-specifichybridization.Eg.HybridMaize.
Intra-varietal–Crossbet.twoplantsofdiff.genotypesbut
samevariety.
Inter-specific–Crossbet.twospeciesofgenus-Eg.Wheat,
Cotton,Tobacco.
Inter-generic–Crossbet.twodiff.genera.
Eg.SugarcaneXBamboo,WheatXRye,RadishXCabbage.

2. OBJECTIVES
•Toevolveavarietywithdesirablecharacters.Eg.high
yield,goodquality,diseaseresistance,droughttolerance,
etc.
•Toproduceusefulvariationsbyintroducing
recombinationofcharacters.
•Toproduceandutilizehybridvigor.
PROCEDURE/TECHNIQUESOFHYBRIDIZATION
Thefollowinginformationareessentialforcrossing
•Detailsofmaleparent.
•Detailsoffemaleparent.
•Whetherplantsareunisexualorbisexual.
•Timeofanthesis.
•Timeofharvestingofplants.
•Whetherflowersareselforcrosspollinated.
OBJECTIVES
•Toevolveavarietywithdesirablecharacters.Eg.high
yield,goodquality,diseaseresistance,droughttolerance,
etc.
•Toproduceusefulvariationsbyintroducing
recombinationofcharacters.
•Toproduceandutilizehybridvigor.
PROCEDURE/TECHNIQUESOFHYBRIDIZATION
Thefollowinginformationareessentialforcrossing
•Detailsofmaleparent.
•Detailsoffemaleparent.
•Whetherplantsareunisexualorbisexual.
•Timeofanthesis.
•Timeofharvestingofplants.
•Whetherflowersareselforcrosspollinated.

3. SELECTION OF PARENTS
•Firststepinhybridization.
•Desirablemale&femaleplantsareselected.
•Parentplantsshouldbehealthy&vigorous.
•Parentstobegrowninisolation&self
pollinatedtobringhomozygosityindesirable
traits.
•Allimportantcharacterstobecombinedshould
bekeptinmind.
•Bothparentsshouldmatureatthesametime.
SELECTION OF PARENTS
•Firststepinhybridization.
•Desirablemale&femaleplantsareselected.
•Parentplantsshouldbehealthy&vigorous.
•Parentstobegrowninisolation&self
pollinatedtobringhomozygosityindesirable
traits.
•Allimportantcharacterstobecombinedshould
bekeptinmind.
•Bothparentsshouldmatureatthesametime.

4. SELFING OF PARENTS
•2
nd
stepinhybridization.
•Maketheparentspureinitscharacters.
•Donebyartificialselffertilization.
•Bisexualflowers-coveredusingpaperbagsbefore
anthesistopreventnaturalcrosspollination.
•Selfpollinationwilloccurinsidethepaperbags.
•Incrosspollinatedcropsmale&femaleflowersare
baggedseparatelybeforeanthesis.
•Whenstigmabecomesreceptive,pollengrainsare
collected&brushedonstigma–thisisartificial
pollination.
•Processcontinuedtillparentbecomeshomozygousor
pureforitsparticularcharacter.
SELFING OF PARENTS
•2
nd
stepinhybridization.
•Maketheparentspureinitscharacters.
•Donebyartificialselffertilization.
•Bisexualflowers-coveredusingpaperbagsbefore
anthesistopreventnaturalcrosspollination.
•Selfpollinationwilloccurinsidethepaperbags.
•Incrosspollinatedcropsmale&femaleflowersare
baggedseparatelybeforeanthesis.
•Whenstigmabecomesreceptive,pollengrainsare
collected&brushedonstigma–thisisartificial
pollination.
•Processcontinuedtillparentbecomeshomozygousor
pureforitsparticularcharacter.

5. EMASCULATION
•3
rd
stepinhybridization.
•Removalofstamensfromfemaleparentbefore
theyburst&shedpollen.
•Donetopreventselfpollination.
•Doneinflowerbudsexpectedtoopeninthe
followingday.
•Suchflowerbudsarerecognizedbytheir
enlargedunopenedcorolla.
•Emasculationcanbedonebyanyofthe
followingmethods.
EMASCULATION
•3
rd
stepinhybridization.
•Removalofstamensfromfemaleparentbefore
theyburst&shedpollen.
•Donetopreventselfpollination.
•Doneinflowerbudsexpectedtoopeninthe
followingday.
•Suchflowerbudsarerecognizedbytheir
enlargedunopenedcorolla.
•Emasculationcanbedonebyanyofthe
followingmethods.

6. FORECEPS AND SCISSORS METHOD
•Doneinlargeflowers.
•Budsareopened&anthersremovedusingsterileforceps&
needlesorscissors.
•Noinjurytobecausedtootherfloralparts–calyx,corolla&
especiallypistil.
HOTORCOLDWATERORALCOHOLTREATMENT
•Forsmallflowerslikethatofrice,sorghum,etc.thatare
difficulttobeemasculatedbyforceps,scissors,etc.
•Emasculationisdonebydippingpaniclesinhotwaterfora
definiteperiod.
•Idealtemperatureisbetween45
o
Cand50
o
C.
•Gynoeciacanwithstandatemperatureatwhichanthersare
killed.
•Alsodonebydippinginflorescenceincoldwateroralcohol
foradefiniteperiod.
FORECEPS AND SCISSORS METHOD
•Doneinlargeflowers.
•Budsareopened&anthersremovedusingsterileforceps&
needlesorscissors.
•Noinjurytobecausedtootherfloralparts–calyx,corolla&
especiallypistil.
HOTORCOLDWATERORALCOHOLTREATMENT
•Forsmallflowerslikethatofrice,sorghum,etc.thatare
difficulttobeemasculatedbyforceps,scissors,etc.
•Emasculationisdonebydippingpaniclesinhotwaterfora
definiteperiod.
•Idealtemperatureisbetween45
o
Cand50
o
C.
•Gynoeciacanwithstandatemperatureatwhichanthersare
killed.
•Alsodonebydippinginflorescenceincoldwateroralcohol
foradefiniteperiod.

7. MALE STERILITY METHOD
•Inselfpollinatedcrops,emasculationiseliminatedby
theuseofmalesterileplantsinwhichanthersare
sterile.
•Malesterilitycanbeinducedbyspraying2,4-D,NAA,
maleichydrazide,etc.onimmatureflowerbuds.
BAGGING
•Afteremasculationflowerbudsarekeptenclosedin
bagsofidealsizes,madeofplastic,cellophaneor
paper.
•Bagsaretiedbythread,wire,pins,etc.
•Thisprocessiscalledbagging.
•Bothmale&femaleflowers-baggedseparatelyto
preventcontamination(foreignpollen).
•Baggingisusuallydonebeforeanthesis.
MALE STERILITY METHOD
•Inselfpollinatedcrops,emasculationiseliminatedby
theuseofmalesterileplantsinwhichanthersare
sterile.
•Malesterilitycanbeinducedbyspraying2,4-D,NAA,
maleichydrazide,etc.onimmatureflowerbuds.
BAGGING
•Afteremasculationflowerbudsarekeptenclosedin
bagsofidealsizes,madeofplastic,cellophaneor
paper.
•Bagsaretiedbythread,wire,pins,etc.
•Thisprocessiscalledbagging.
•Bothmale&femaleflowers-baggedseparatelyto
preventcontamination(foreignpollen).
•Baggingisusuallydonebeforeanthesis.

8. MALE PARENT
•Unopenedflowerbudsofmaleparentwhether
unisexualorbisexual,arecoveredaslikefemale
parenttopreventcontaminationofforeign
pollengrains.
•Thisistoensurethatpollenofbaggedflowers
areofthesameplantandnotofanyotherplant.
COLLECTIONANDSTORAGEOFPOLLEN
•Pollengrainsforcrossingarecollectedfrom
baggedmaleflowers.
•Pollen/antherscollectedinpetridishesorpaper
bagsjustafterdehiscence.
•Storedinvialsorcapsulesforfutureuse.
MALE PARENT
•Unopenedflowerbudsofmaleparentwhether
unisexualorbisexual,arecoveredaslikefemale
parenttopreventcontaminationofforeign
pollengrains.
•Thisistoensurethatpollenofbaggedflowers
areofthesameplantandnotofanyotherplant.
COLLECTIONANDSTORAGEOFPOLLEN
•Pollengrainsforcrossingarecollectedfrom
baggedmaleflowers.
•Pollen/antherscollectedinpetridishesorpaper
bagsjustafterdehiscence.
•Storedinvialsorcapsulesforfutureuse.

9. CROSSING OR CROSS POLLINATION
•5
th
stepinhybridization.
•Itisdefinedasartificialcrosspollination
betweengeneticallyunlikeparents.
•Viablepolleniscollectedfromdesiredmale
plant&transferredontothestigmaofthe
desiredemasculatedfemaleparent.
•Pollengrainsarecollectedinpetridishes.
•Bagistemporarilyremovedfromthefemale
parent&thecollectedpollenaredustedon
stigma.
CROSSING OR CROSS POLLINATION
•5
th
stepinhybridization.
•Itisdefinedasartificialcrosspollination
betweengeneticallyunlikeparents.
•Viablepolleniscollectedfromdesiredmale
plant&transferredontothestigmaofthe
desiredemasculatedfemaleparent.
•Pollengrainsarecollectedinpetridishes.
•Bagistemporarilyremovedfromthefemale
parent&thecollectedpollenaredustedon
stigma.

10. •IncropslikeBajara,Jowar,etc.handcrosspollinationis
tedious,sinceflowersaresmall.
•Insuchcropsmale&femaleplantsaregrownsidebyside&
male&femaleinflorescencesareenclosedinonebag.
•Herecrossingtakesplaceinsidethebagautomatically.
•Crossingisnormallydoneatthetimeofanthesis,dehiscence
&stigmareceptivity.
•Dehiscenceofanthercanberecognizedbytheyellowish
powderymass.
•Stigmareceptivityisevidentbythepresenceoffluidonits
surface.
•Aftercrossingfemaleflowersareagainbagged.
•IncropslikeBajara,Jowar,etc.handcrosspollinationis
tedious,sinceflowersaresmall.
•Insuchcropsmale&femaleplantsaregrownsidebyside&
male&femaleinflorescencesareenclosedinonebag.
•Herecrossingtakesplaceinsidethebagautomatically.
•Crossingisnormallydoneatthetimeofanthesis,dehiscence
&stigmareceptivity.
•Dehiscenceofanthercanberecognizedbytheyellowish
powderymass.
•Stigmareceptivityisevidentbythepresenceoffluidonits
surface.
•Aftercrossingfemaleflowersareagainbagged.

11. LABELLING
•Emasculated&crossedflowersareproperlybagged,
tagged&labeled.
•Labelingisdoneeitheronbagitselforonseparate
labels.
•Labelsaretaggedtobagsusingthread.
•Labelshouldbearfollowingdetails–
Referencenumber
Dateofemasculation
Dateofcrossing
Detailsofmaleandfemaleparents
LABELLING
•Emasculated&crossedflowersareproperlybagged,
tagged&labeled.
•Labelingisdoneeitheronbagitselforonseparate
labels.
•Labelsaretaggedtobagsusingthread.
•Labelshouldbearfollowingdetails–
Referencenumber
Dateofemasculation
Dateofcrossing
Detailsofmaleandfemaleparents

12. COLLECTION OF HYBRID SEEDS
•Aftermaturityofseeds,crossedheadsof
desirablecharactersareharvested&collected
alongwithlabelsinseparateenvelopes.
•Inthenextseason,seedsofeachheadaresown
separatelytoraiseF1generation.
•AllplantsofF1aregeneticallysimilar&look
exactlyalike.
•PlantsofF1areprogeniesofcrossedparents&
arehybrids.
•Theymayexhibithybridvigor–increased
growth,size,yield,function,etc.overthe
parents.
COLLECTION OF HYBRID SEEDS
•Aftermaturityofseeds,crossedheadsof
desirablecharactersareharvested&collected
alongwithlabelsinseparateenvelopes.
•Inthenextseason,seedsofeachheadaresown
separatelytoraiseF1generation.
•AllplantsofF1aregeneticallysimilar&look
exactlyalike.
•PlantsofF1areprogeniesofcrossedparents&
arehybrids.
•Theymayexhibithybridvigor–increased
growth,size,yield,function,etc.overthe
parents.

13. METHODS OF HYBRIDIZATION
•HandlingofF1&subsequentgenerationsis
carriedoutbydifferentselectionmethods.
•Methodsofhybridizationaredifferentforself&
crosspollinatedcrops.
HYBRIDIZATIONOFSELFPOLLINATEDCROPS
•Selectionmethodsofhybridizationinself
pollinatedcropsareasfollows.
•Selfpollinatedcropsinclude–wheat,barley,
oats,rice,cotton,tobacco,potato,peas,beans,
etc.
METHODS OF HYBRIDIZATION
•HandlingofF1&subsequentgenerationsis
carriedoutbydifferentselectionmethods.
•Methodsofhybridizationaredifferentforself&
crosspollinatedcrops.
HYBRIDIZATIONOFSELFPOLLINATEDCROPS
•Selectionmethodsofhybridizationinself
pollinatedcropsareasfollows.
•Selfpollinatedcropsinclude–wheat,barley,
oats,rice,cotton,tobacco,potato,peas,beans,
etc.

14. PEDIGREE METHOD
•DesirablehybridsofF1generationare
selectedonthebasisofdesiredcharacters.
•Seedsfromeachselectedplantarecollected
&grownseparatelyinrowstoraiseF2.
•FromF2thebestperformersareselected&
seedsfromtheseplantsaresownseparately
inrowstoraiseF3.
•ProcessrepeatedtillF6producedbecomes
homozygous&fairlyuniform.
PEDIGREE METHOD
•DesirablehybridsofF1generationare
selectedonthebasisofdesiredcharacters.
•Seedsfromeachselectedplantarecollected
&grownseparatelyinrowstoraiseF2.
•FromF2thebestperformersareselected&
seedsfromtheseplantsaresownseparately
inrowstoraiseF3.
•ProcessrepeatedtillF6producedbecomes
homozygous&fairlyuniform.

15. •Undesirablevarietiesarediscardedduring
selectionprocess.
•Plantsuniformindesirablestrainsare
harvested&bulkedtogethertoconstitutea
variety.
•Selectedvarietyisfurthertestedforyield&
adaptabilityindifferentlocalities.
•Finallythevarietyisnamed,multiplied&
distributedtofarmers.
•Inthismethodacompleteancestralrecord
(pedigree)ofeachprogenyismaintained.
•Undesirablevarietiesarediscardedduring
selectionprocess.
•Plantsuniformindesirablestrainsare
harvested&bulkedtogethertoconstitutea
variety.
•Selectedvarietyisfurthertestedforyield&
adaptabilityindifferentlocalities.
•Finallythevarietyisnamed,multiplied&
distributedtofarmers.
•Inthismethodacompleteancestralrecord
(pedigree)ofeachprogenyismaintained.

16. BULK METHOD
•F1hybridplantsaregrowninbulk.
•Theirseedsareharvested&collectedtogether–
usedtoraiseF2generation.
•FromF2desirableplantsareselected&seedsare
bulkedtogether-seedsusedtoraiseF3
population.
•FromF3suitableplantsareselected,seeds
collected&bulkedtogether.
•ProcessrepeatedtillF6orF7generationstill
homozygosityisachieved.
•Plantswithsuperiorqualityarenamed&released
tofarmersforcultivation.
•Thisisdoneafteryieldtrialsaredoneatdifferent
stations.
BULK METHOD
•F1hybridplantsaregrowninbulk.
•Theirseedsareharvested&collectedtogether–
usedtoraiseF2generation.
•FromF2desirableplantsareselected&seedsare
bulkedtogether-seedsusedtoraiseF3
population.
•FromF3suitableplantsareselected,seeds
collected&bulkedtogether.
•ProcessrepeatedtillF6orF7generationstill
homozygosityisachieved.
•Plantswithsuperiorqualityarenamed&released
tofarmersforcultivation.
•Thisisdoneafteryieldtrialsaredoneatdifferent
stations.

17. BACK CROSS METHOD
•Methodisemployedfortheimprovementofboth
self&crosspollinatedcrops.
•Thiscrossistotransferaparticularqualityofone
parenttoanotherlackingit.
•Diseaseresistance,droughttolerance,etc.are
introducedintosusceptiblecropswithothergood
qualities.
•Thishybridisbackcrossedtothedesirablevariety.
•ProcessiscontinuedtillF6.
•Plantsareallowedtoselfpollinatesoastoobtain
homozygosityfortheintroducedcharacters.
BACK CROSS METHOD
•Methodisemployedfortheimprovementofboth
self&crosspollinatedcrops.
•Thiscrossistotransferaparticularqualityofone
parenttoanotherlackingit.
•Diseaseresistance,droughttolerance,etc.are
introducedintosusceptiblecropswithothergood
qualities.
•Thishybridisbackcrossedtothedesirablevariety.
•ProcessiscontinuedtillF6.
•Plantsareallowedtoselfpollinatesoastoobtain
homozygosityfortheintroducedcharacters.

18. •Inbackcrosssystem–desirablevarietyis
knownasrecurrentorrecipientvariety.
•Undesirablevarietypossessingacharacter
whichislackinginthedesirablevarietyis
knownasdonorparent.
Eg.Aisagoodordesirablevarietybutitis
diseasesusceptible.
Bisaninferiorvarietybutdiseaseresistant.
HereAisrecipientandBisdonor.The
desirablecharacterie;diseaseresistanceofB
istransferredtoAbycrossingAandB.Here
AisfemaleparentandBisthemaleparent.
•Inbackcrosssystem–desirablevarietyis
knownasrecurrentorrecipientvariety.
•Undesirablevarietypossessingacharacter
whichislackinginthedesirablevarietyis
knownasdonorparent.
Eg.Aisagoodordesirablevarietybutitis
diseasesusceptible.
Bisaninferiorvarietybutdiseaseresistant.
HereAisrecipientandBisdonor.The
desirablecharacterie;diseaseresistanceofB
istransferredtoAbycrossingAandB.Here
AisfemaleparentandBisthemaleparent.

19. •TheF1insteadofallowingtoselfpollinate,itis
backcrossedtoAtotransfergenesofdesirable
quality.
•ThisbackcrossgenerationisnamedasBC1.
•TheplantsofBC1arefurtherbackcrossedtoAto
raisetheBC2generation.
•BackcrossingisrepeateduptoBC7generation.
•Nowtheplantswillbehomozygousforalldesirable
charactersofAparentand50%genesfordisease
resistance.
•AtBC7plantsareallowedtoselfpollinate&they
becomehomozygousforallcharactersincluding
diseaseresistanceandtheseplantsareselected.
•TheF1insteadofallowingtoselfpollinate,itis
backcrossedtoAtotransfergenesofdesirable
quality.
•ThisbackcrossgenerationisnamedasBC1.
•TheplantsofBC1arefurtherbackcrossedtoAto
raisetheBC2generation.
•BackcrossingisrepeateduptoBC7generation.
•Nowtheplantswillbehomozygousforalldesirable
charactersofAparentand50%genesfordisease
resistance.
•AtBC7plantsareallowedtoselfpollinate&they
becomehomozygousforallcharactersincluding
diseaseresistanceandtheseplantsareselected.

20. A(female)XB(malewithdiseaseresistance)
HybridF1XA
HybridBC1XA
HybridBC2XA
HybridBC3XA
HybridBC6---allowedtoselfpollinate.
(Plants with all good qualities of A + disease resistance)
Backcrossmethodisregardedbestbecause–
Therequiredcharacterofaplantcanbebroughteasilyintothedesirablevariety.
Fertilityisestablishedandsterilitycanbeminimizedafterrepeatedbackcrossing.
A(female)XB(malewithdiseaseresistance)
HybridF1XA
HybridBC1XA
HybridBC2XA
HybridBC3XA
HybridBC6---allowedtoselfpollinate.
(Plants with all good qualities of A + disease resistance)
Backcrossmethodisregardedbestbecause–
Therequiredcharacterofaplantcanbebroughteasilyintothedesirablevariety.
Fertilityisestablishedandsterilitycanbeminimizedafterrepeatedbackcrossing.

21. MULTIPLE CROSS METHOD
•Aseriesofbridgecrossesaremade.
•Desirablemonogeniccharactersfoundscatteredinmanypureline
parentsarecombinedtogetherinonevariety.
•Ifthereareeightvarietieseachwithonegoodquality,thenthe
qualitiesoftheseeightvarietiesarecombinedintoone.
I AXB CXD EXF GXH------Singlecrosses
IIABX CDXEFXGH ------Doublecrosses
III ABCD X EFGH-------Multiplecross
ABCDEFGH--Hybrid
•HybridsofmultiplecrossesareselfedandF2israised.
•Furtherbreedingiscarriedouteitherbypedigreeorbulkmethodof
selection.
MULTIPLE CROSS METHOD
•Aseriesofbridgecrossesaremade.
•Desirablemonogeniccharactersfoundscatteredinmanypureline
parentsarecombinedtogetherinonevariety.
•Ifthereareeightvarietieseachwithonegoodquality,thenthe
qualitiesoftheseeightvarietiesarecombinedintoone.
I AXB CXD EXF GXH------Singlecrosses
IIABX CDXEFXGH ------Doublecrosses
III ABCD X EFGH-------Multiplecross
ABCDEFGH--Hybrid
•HybridsofmultiplecrossesareselfedandF2israised.
•Furtherbreedingiscarriedouteitherbypedigreeorbulkmethodof
selection.

22. HYBRIDIZATION IN CROSS POLLINATED CROPS
•Commoncrosspollinatedcropsinclude–maize,rye,
cucurbits,fruittreesandforagecrops.
•Inthesecropsdesirablecharactersarefoundscatteredin
differentpurelines(inbreds).
•Thecharacterscanbecombinedinanyofthefollowingways
-
Singlecross,Threewaycross,Syntheticcross,Double
crossandTopcross.
SINGLECROSS
•Itisthecrossbetweentwoinbreeds(purelines)Eg.AXBor
CXD.
•Hybridsaredirectlydistributedtofarmersforcultivation
purpose.
HYBRIDIZATION IN CROSS POLLINATED CROPS
•Commoncrosspollinatedcropsinclude–maize,rye,
cucurbits,fruittreesandforagecrops.
•Inthesecropsdesirablecharactersarefoundscatteredin
differentpurelines(inbreds).
•Thecharacterscanbecombinedinanyofthefollowingways
-
Singlecross,Threewaycross,Syntheticcross,Double
crossandTopcross.
SINGLECROSS
•Itisthecrossbetweentwoinbreeds(purelines)Eg.AXBor
CXD.
•Hybridsaredirectlydistributedtofarmersforcultivation
purpose.

23. DOUBLE CROSS
•ItisacrossbetweentheF1hybridsoftwo
differentsinglecrosses,eachinvolvingtwo
differentinbreeds.
1
st
singlecrossAXB
2
nd
singlecrossCXD
F1hybridABXF1Hybrid CD
ABCDDoublecrosshybrid
DOUBLE CROSS
•ItisacrossbetweentheF1hybridsoftwo
differentsinglecrosses,eachinvolvingtwo
differentinbreeds.
1
st
singlecrossAXB
2
nd
singlecrossCXD
F1hybridABXF1Hybrid CD
ABCDDoublecrosshybrid

24. THREE WAY CROSS
•CrossbetweenF1hybridofasinglecross&
aninbredwhichisusedasmaleparent.
AXBSinglecross
AB F1Hybrid
ABXCThreewaycross
THREE WAY CROSS
•CrossbetweenF1hybridofasinglecross&
aninbredwhichisusedasmaleparent.
AXBSinglecross
AB F1Hybrid
ABXCThreewaycross

25. DIFFICULTIES IN CONDUCTING HYBRIDIZATION
•Isolation of suitable parents hybrids
Mostdifficultpartofhybridizationistoisolatethe
desirableinbredstobeusedasparentsandthehybridsto
constitutethevariety.Thisrequirescarefulobservation,
thoroughfieldtesting,keepingrecords,etc.
•Differenttimesofmaturity
Usuallyplantsgrowninthesameseasonareselectedfor
crossingbuttheymaynotflowertogetherdueto
differenceintheirtimeofmaturity.Thiscanbecorrected
byadjustingthesowingperiodinsuchawaythatboth
maleandfemaleplantsflowersimultaneously.Insome
casespollengrainsarepreserved.
DIFFICULTIES IN CONDUCTING HYBRIDIZATION
•Isolation of suitable parents hybrids
Mostdifficultpartofhybridizationistoisolatethe
desirableinbredstobeusedasparentsandthehybridsto
constitutethevariety.Thisrequirescarefulobservation,
thoroughfieldtesting,keepingrecords,etc.
•Differenttimesofmaturity
Usuallyplantsgrowninthesameseasonareselectedfor
crossingbuttheymaynotflowertogetherdueto
differenceintheirtimeofmaturity.Thiscanbecorrected
byadjustingthesowingperiodinsuchawaythatboth
maleandfemaleplantsflowersimultaneously.Insome
casespollengrainsarepreserved.

26. •Incompatibility and sterility
Thisiscommoninbothinterspecificandinter
genericcrosses.Theincompatibilitymaybedue
tolackofpollengermination,failureof
fertilization,etc.Hybridpollensterilityisthe
mainhandicapinintergenericcrossesdueto
geneimbalance.
•Flowerdamageduringemasculation
Sometimesduringemasculationtechniquethe
flowerscangetinjuredordamagedleadingto
failureinhybridization.
•Incompatibility and sterility
Thisiscommoninbothinterspecificandinter
genericcrosses.Theincompatibilitymaybedue
tolackofpollengermination,failureof
fertilization,etc.Hybridpollensterilityisthe
mainhandicapinintergenericcrossesdueto
geneimbalance.
•Flowerdamageduringemasculation
Sometimesduringemasculationtechniquethe
flowerscangetinjuredordamagedleadingto
failureinhybridization.