Breeding Self-polinated Crops

8/19/2019 Breeding Self-polinated Crops

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BreedingBreeding

Self Pollinated CropsSelf Pollinated Crops


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CultivarCultivar

Is a group of genetically similar plants,Is a group of genetically similar plants,

which may be identied (by some means)which may be identied (by some means)

from other groups of genetically similarfrom other groups of genetically similar

plantsplants

ssential Characteristics!ssential Characteristics!

• Identity! cultivar must beIdentity! cultivar must be

distinguishable from other cultivarsdistinguishable from other cultivars

• "eproducibility! the distinguishing"eproducibility! the distinguishing

characteristic(s) need to be reproducedcharacteristic(s) need to be reproduced

in the progeny faithfullyin the progeny faithfully

CultivarsCultivars


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#ypes of Cultivars#ypes of Cultivars

$pen%Pollinated cultivars$pen%Pollinated cultivars $&P& seeds are a result of either natural$&P& seeds are a result of either natural

or human selection for specic traitsor human selection for specic traitswhich are then reselected in everywhich are then reselected in every

crop&crop&

#he seed is 'ept true to type through#he seed is 'ept true to type through

selection and isolation the owers ofselection and isolation the owers ofopen%pollinated or $&P& seed varietiesopen%pollinated or $&P& seed varietiesare pollinated by bees or wind&are pollinated by bees or wind&


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#ypes of Cultivars#ypes of Cultivars

Synthetic cultivarsSynthetic cultivars * population developed by inter%* population developed by inter%

crossing a set of good combiner inbredcrossing a set of good combiner inbred

lines with subse+uent maintenancelines with subse+uent maintenancethrough open%pollination&through open%pollination&

#he components of synthetics are#he components of synthetics are

inbreds or clones so the cultivar can beinbreds or clones so the cultivar can be

periodically reconstituted&periodically reconstituted&


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ulti%line cultivarsulti%line cultivars

* mi-ture of isolines each of which is* mi-ture of isolines each of which isdi.erent for a single gene controllingdi.erent for a single gene controllingdi.erent forms of the same characterdi.erent forms of the same character(e&g&, for di.erent races of pathogens)(e&g&, for di.erent races of pathogens)

/0 cultivars/0 cultivars#he rst generation of o.spring from a#he rst generation of o.spring from across of genetically di.erent plantscross of genetically di.erent plants

Pure%line cultivarsPure%line cultivars#he progeny of a single homo1ygous#he progeny of a single homo1ygousindividual produced through self%individual produced through self%pollinationpollination

Types of CultivarsTypes of Cultivars


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Cultivars and Self%pollinatedCultivars and Self%pollinated

CropsCrops

In self%pollinated species!In self%pollinated species! 2omo1ygous loci will remain homo1ygous2omo1ygous loci will remain homo1ygous

following self%pollinationfollowing self%pollination

2etero1ygous loci will segregate2etero1ygous loci will segregateproducing half homo1ygous progeny andproducing half homo1ygous progeny andhalf hetero1ygous progenyhalf hetero1ygous progeny

Plants selected from mi-ed populationsPlants selected from mi-ed populationsafter 3%4 self generations will normallyafter 3%4 self generations will normallyhave reached a practical level ofhave reached a practical level ofhomo1ygosityhomo1ygosity


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In general, a mi-ed population of self%In general, a mi-ed population of self%pollinated plants is composed of plants withpollinated plants is composed of plants with

di.erent homo1ygous genotypes (i&e&, adi.erent homo1ygous genotypes (i&e&, a

heterogeneous population of homo1ygotesheterogeneous population of homo1ygotes

If single plants are selected from thisIf single plants are selected from this

population and seed increased, each plantpopulation and seed increased, each plant

will produce a 5pure6 population, but eachwill produce a 5pure6 population, but each

population will be di.erent, based on thepopulation will be di.erent, based on the

parental selectionparental selection

Cultivars and Self%pollinatedCultivars and Self%pollinated

CropsCrops


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Selection involves the I7 and propagation ofSelection involves the I7 and propagation ofindividual genotypes from a land raceindividual genotypes from a land racepopulation, or following designedpopulation, or following designedhybridi1ationshybridi1ations

8enetic variation must be identied and8enetic variation must be identied anddistinguished from environment%baseddistinguished from environment%basedvariationvariation

Selection procedures practiced in mi-edSelection procedures practiced in mi-edpopulations of self%pollinated crops can bepopulations of self%pollinated crops can bedivided into two selection proceduresdivided into two selection procedures

Breeding Self%pollinatedBreeding Self%pollinated

CropsCrops


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Breeding ethods of SelfBreeding ethods of Self

Pollinated CropsPollinated Crops0&0& Pure linePure line

9&9& assass:&:& Bul' Bul'

;&;& PedigreePedigree

3&3& Single Seed 7escentSingle Seed 7escent (modiedmodiedpedigree)pedigree)


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Pure =inePure =ine


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Pure =ine! ("ecount >ohannsen&Pure =ine! ("ecount >ohannsen&

0?@:)0?@:)

usually no hybridi1ationusually no hybridi1ation

Initial parents (IPs) selected from aInitial parents (IPs) selected from a

heterogenous population (i&e&heterogenous population (i&e&genetically variable)genetically variable)

procedure continues until homogeneityprocedure continues until homogeneity

is achievedis achieved

last phase is eld testinglast phase is eld testing


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* pure line consists of progeny* pure line consists of progeny

descended solely by self%pollinationdescended solely by self%pollination

from a single homo1ygous plantfrom a single homo1ygous plant

Pure line selection is therefore aPure line selection is therefore a

procedure for isolating pure line(s)procedure for isolating pure line(s)

from a mi-ed populationfrom a mi-ed population

Pure%line SelectionPure%line Selection


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Pure line cultivars are more uniform thanPure line cultivars are more uniform thancultivars developed through mass selectioncultivars developed through mass selection

(by denition, a pure line cultivar will be(by denition, a pure line cultivar will be

composed of plants with a single genotype)composed of plants with a single genotype)

Progeny testing is an essential componentProgeny testing is an essential component

of pure line selectionof pure line selection

Improvement using pure line breeding isImprovement using pure line breeding is

limited to the isolation of the 5best6limited to the isolation of the 5best6

genotypes present in the mi-ed populationgenotypes present in the mi-ed population



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ore e.ective than S in developmentore e.ective than S in developmentof self%pollinated cultivarsof self%pollinated cultivars

2owever, leads to rapid depletion of2owever, leads to rapid depletion ofgenetic variationgenetic variation

8enetic variability can be managed8enetic variability can be managed

through directed cross hybridi1ationsthrough directed cross hybridi1ations

ssential to progeny test selectionsssential to progeny test selections


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Pure%line Selection%Pure%line Selection%

StepsSteps

Select desirable plantsSelect desirable plants

• Aumber depends on variation of originalAumber depends on variation of originalpopulation, space and resources forpopulation, space and resources forfollowing year progeny testsfollowing year progeny tests

• Selecting too few plants may ris' losingSelecting too few plants may ris' losingsuperior genetic variationsuperior genetic variation

• * genotype missed early is lost forever* genotype missed early is lost forever

Seed from each selection is harvestedSeed from each selection is harvested

individuallyindividually


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Pure%line Selection%StepsPure%line Selection%StepsSingle plant progeny rows grown outSingle plant progeny rows grown out

• valuate for desirable traits and uniformityvaluate for desirable traits and uniformity• Should use severe selection criteria (rogue out allShould use severe selection criteria (rogue out all

poor, unpromising and variable progenies)poor, unpromising and variable progenies)

Selected progenies are harvestedSelected progenies are harvestedindividuallyindividually

In subse+uent years, run replicated yieldIn subse+uent years, run replicated yield

trials with selection of highest yielding plantstrials with selection of highest yielding plants

*fter ;%< rounds, highest yielding plant is put*fter ;%< rounds, highest yielding plant is put

forward as a new cultivarforward as a new cultivar


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*dvantages*dvantages

0&0& I7 of best pure line reects ma-imumI7 of best pure line reects ma-imum

genetic advance from a variablegenetic advance from a variable

population no 5poor6 plants maintainedpopulation no 5poor6 plants maintained

9&9& 2igher degree of uniformity2igher degree of uniformity

:&:& Selection based on progeny performanceSelection based on progeny performance

is e.ective for characters with relativelyis e.ective for characters with relatively

low hlow h99


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0&0& "e+uires relatively more time, space,"e+uires relatively more time, space,and resources for progeny testing thanand resources for progeny testing thanS to develop new cultivarS to develop new cultivar

9&9& 2igh degree of genetic uniformity more2igh degree of genetic uniformity moregenetically vulnerable and lessgenetically vulnerable and lessadaptable to uctuating environmentsadaptable to uctuating environments

:&:& I7 and multiplication of one outstandingI7 and multiplication of one outstandingpure%line depletes available geneticpure%line depletes available geneticvariation leads to fast genetic erosionvariation leads to fast genetic erosion

7isadvantages7isadvantages


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2ow long will a cultivar remain pure2ow long will a cultivar remain pure

0&0& *s long as the commercial life of the*s long as the commercial life of thecultivar, unless!cultivar, unless!• Seed becomes contaminated with seedSeed becomes contaminated with seed

from other sources (e&g& from harvestingfrom other sources (e&g& from harvestingand seed cleaning e+uipment)and seed cleaning e+uipment)

• Aatural out%crossing occurs (amountAatural out%crossing occurs (amountvaries by species but seldom e-ceeds 0%varies by species but seldom e-ceeds 0%9 in self%pollinated crops)9 in self%pollinated crops)

• utations occurutations occur9&9& #o maintain purity, o.%types arising from#o maintain purity, o.%types arising from

mutation or out%crossing must be roguedmutation or out%crossing must be roguedoutout


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ass Selectionass Selection


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ay or may not include hybridi1ationay or may not include hybridi1ation

a'e IP selections based on single, ideal ora'e IP selections based on single, ideal or

desirable phenotype and BD=E seeddesirable phenotype and BD=E seed

ay repeat or go directly to performanceay repeat or go directly to performance

testingtestingass Selection has 9 important functions!ass Selection has 9 important functions!

0&0& "apid improvement in land%race or mi-ed"apid improvement in land%race or mi-ed

cultivarscultivars

9&9& aintenance of e-isting cultivars (sometimesaintenance of e-isting cultivars (sometimes

purication)purication)

FF any pb6ers of self pollinated crops believeany pb6ers of self pollinated crops believe

that combining closely related pure linesthat combining closely related pure linesG HG H

ass Selectionass Selection


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Success depends on e-tent ofSuccess depends on e-tent of

variation and hvariation and h99 of the traits ofof the traits of

interestinterest

=and races ma'e an ideal starting=and races ma'e an ideal starting

sourcesource• 2igh genetic variability accumulated2igh genetic variability accumulated

over generations of mutation andover generations of mutation and

natural hybridi1ationnatural hybridi1ation


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ass Selectionass SelectionInitial selectionInitial selection

Can be either a positive or a negativeCan be either a positive or a negative

selectionselection

Aegative screening! * screeningAegative screening! * screeningtechni+ue designed to identify andtechni+ue designed to identify and

eliminate the least desirable plants&eliminate the least desirable plants&

positive screening! which involvespositive screening! which involves

identifying and preserving the mostidentifying and preserving the most

desirable plants&desirable plants&

ass Selection 0ass Selection 0stst


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ass Selection % 0ass Selection % 0stst ear ear

Select plants with respect to height,Select plants with respect to height,maturity, grain si1e, and any other traitsmaturity, grain si1e, and any other traits

that have 5production6 or 5acceptability6that have 5production6 or 5acceptability6

issuesissues

Bul' seed (may 5bloc'6 these bul's if wideBul' seed (may 5bloc'6 these bul's if wide

variation is present for certain traits e&g&variation is present for certain traits e&g&

height)height)

ay be able to use machines to selectay be able to use machines to select

• 2arvest only tall plants, or save only2arvest only tall plants, or save only

large seed passed through a sievelarge seed passed through a sieve

S l ti 9ass Selection 9ndnd


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ass Selection % 9ass Selection % 9ndnd ear ear

S really only ta'es 0 yr because selectedS really only ta'es 0 yr because selectedseed represents a mi-ture of only theseed represents a mi-ture of only thesuperior pure lines that e-isted in thesuperior pure lines that e-isted in theoriginal populationoriginal population

2owever, additional rounds of selection2owever, additional rounds of selectionand bul'ing will allow for evaluation underand bul'ing will allow for evaluation underdi.erent environments, disease and pestdi.erent environments, disease and pest

pressures&pressures&

*lso, multiple years will allow you to*lso, multiple years will allow you tocompare performance with establishedcompare performance with established

cultivars over years and environments&cultivars over years and environments&


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$bJectives of ass Selection!$bJectives of ass Selection!

0&0& #o increase the fre+uency of#o increase the fre+uency ofsuperior genotypes from asuperior genotypes from a

genetically variable populationgenetically variable population

9&9& Purify a mi-ed population withPurify a mi-ed population with

di.ering phenotypesdi.ering phenotypes

:&:& 7evelop a new cultivar by improving7evelop a new cultivar by improving

the average performancethe average performance of theof thepopulationpopulation


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0&0& Selection based on phenotypicSelection based on phenotypicperformance not e.ective with low hperformance not e.ective with low h99 traitstraits

9&9& Kithout progeny testing, hetero1ygotesKithout progeny testing, hetero1ygotescan be inadvertently selectedcan be inadvertently selected

:&:& Population cannot reali1e ma-imumPopulation cannot reali1e ma-imum

potential displayed by the 5best6 pure line,potential displayed by the 5best6 pure line,due to bul'ingdue to bul'ing

;&;& /inal population is not as uniform as those/inal population is not as uniform as those

developed through pure%line selectiondeveloped through pure%line selection


ass selection vs pure lineass selection vs pure line


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ass selection vs pure lineass selection vs pure lineselectionselection

=ine mi-ture=ine mi-ture

Bul' ofBul' ofphenotypicallphenotypicall

yy

similar plantssimilar plants

Cultivar registerCultivar register

and mar'etingand mar'eting

Single plant o.springsSingle plant o.springs

=0 =9 =:LL&=0 =9 =:LL&

=A=A

"egister and"egister and

mar'etmar'et

the best purethe best pure

lineslines

ass selectionass selection Pure line selectioPure line selectio

2eterogenous cultivars2eterogenous cultivars 2omogenous cultivars2omogenous cultivars



yy





=0 =9 =:LL&=0 =9 =:LL&

=A=A


mar'etmar'et


lineslines





yy





=0 =9 =:LL&=0 =9 =:LL&

=A=A


mar'etmar'et


lineslines




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Bul' ethodBul' ethod


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Bul' Bul'

Inbreed in bul' Inbreed in bul'

to have homo1ygousto have homo1ygous

lineslines

elect superior lineselect superior lines

after /


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0&0& Aatural selection changes gene fre+&Aatural selection changes gene fre+&

via natural survivalvia natural survival

9&9& Breeder may assist nature and discardBreeder may assist nature and discard

obviously poor typesobviously poor types

:&:& "elieves breeder of most record"elieves breeder of most record

'eeping'eeping

;&;& ost of us treat bul's with e-tremelyost of us treat bul's with e-tremely

low inputs and low e-pectations&low inputs and low e-pectations&

Points to consider in Bul' ethodPoints to consider in Bul' ethod


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#he bul' method is a procedure for#he bul' method is a procedure forinbreeding a segregating population untilinbreeding a segregating population untila desired level of homo1ygosity isa desired level of homo1ygosity is

reached&reached&

Seed used to grow each selfed generationSeed used to grow each selfed generationis a sample of the seed harvested in bul'is a sample of the seed harvested in bul'

from the previous generation&from the previous generation&

In the bul' method, seeds harvested inIn the bul' method, seeds harvested inthe /the /00 through /through /;; generations are bul'edgenerations are bul'ed

without selection selection is delayedwithout selection selection is delayeduntil advanced generations (/until advanced generations (/33%/%/44)&)&

By this time, most segregation hasBy this time, most segregation hasstopped&stopped&


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*dvantages*dvantages0&0& =ess record 'eeping than pedigree=ess record 'eeping than pedigree

9&9& Ine-pensiveIne-pensive:&:& asy to handle more crossesasy to handle more crosses

;&;& Aatural selection is primarily forAatural selection is primarily for

competitive abilitycompetitive ability

3&3& ore useful than pedigree method withore useful than pedigree method with

lower hlower h99 traitstraits


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0&0& nvironmental changes from season to season sonvironmental changes from season to season soadaptive advantages shiftadaptive advantages shift

9&9& ost grow bul' seed lots in area of adaptationost grow bul' seed lots in area of adaptation

:&:&

=ess eNcient than pedigree method on highly=ess eNcient than pedigree method on highlyheritable traits (because can purge non%selectionsheritable traits (because can purge non%selectionsin early generations)in early generations)

;&;& Aot useful in selecting plant types at aAot useful in selecting plant types at acompetitive disadvantage (dwarf types)competitive disadvantage (dwarf types)

3&3& /inal genotypes may be able to withstand/inal genotypes may be able to withstandenvironmental stress, but may not be highestenvironmental stress, but may not be highestyieldingyielding


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Pedigree ethodPedigree ethod


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ost popularost popular

ssentially a plant to row system tossentially a plant to row system to

develop near pure linesdevelop near pure lines

/ollowed by performance testing of/ollowed by performance testing of

resulting strainsresulting strains

#his method and its variants re+uire a#his method and its variants re+uire alot of record 'eepinglot of record 'eeping

Pedigree ethodPedigree ethod


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PedigreePedigree

SelectionSelection

duringduring

inbreedinginbreeding

arlyarly

generations!generations!

2igh2ighheritabilityheritability

traitstraits

=ate=ate

generations!generations!

lowlowheritabilityheritability


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8enetic Considerations!8enetic Considerations!

0&0&

*dditive genetic variability decreases*dditive genetic variability decreases

within lines and increases among lines,within lines and increases among lines,

assuming no selectionassuming no selection

recall the movement toward homo1ygosityrecall the movement toward homo1ygosity

following the hybridi1ation of unli'e andfollowing the hybridi1ation of unli'e andhomo1ygous parentshomo1ygous parents

9&9&7ominant genetic variability complicates7ominant genetic variability complicates

pedigree selection homo1ygous andpedigree selection homo1ygous and

hetero1ygous individuals loo' ali'e andhetero1ygous individuals loo' ali'e and

therefore you may continually select thetherefore you may continually select the

hetero1ygotehetero1ygote

#2DS, selection can be discontinued with#2DS, selection can be discontinued with


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0&0& liminates unpromising material at earlyliminates unpromising material at earlystagesstages

9&9& ulti%year records allow good overview ofulti%year records allow good overview of

inheritance, and more e.ective selectioninheritance, and more e.ective selection

through trials in di.erent environmentsthrough trials in di.erent environments

:&:& ultiple families (from di.erent /ultiple families (from di.erent /99

individuals) are maintained yieldingindividuals) are maintained yielding

di.erent gene combinations with commondi.erent gene combinations with common

phenotypephenotype

i d7i d t


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0&0& ost labor, time and resource intensiveost labor, time and resource intensive

method usually compromise between Omethod usually compromise between Ocrosses and population si1escrosses and population si1es

9&9& ery dependent on s'ill of breeder inery dependent on s'ill of breeder inrecogni1ing promising materialrecogni1ing promising material

:&:& Aot very e.ective with low hAot very e.ective with low h99 traitstraits

;&;& Slow can usually put through only oneSlow can usually put through only one

generation per year, and the rightgeneration per year, and the rightenvironmental conditions must be at handenvironmental conditions must be at handfor accurate selection&for accurate selection&

3&3& Dpper ceiling set by allelic contents of /Dpper ceiling set by allelic contents of /99


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ingle Seed 7esceningle Seed 7escen


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ingle Seed 7escentingle Seed 7escent

Inbreed with one seedInbreed with one seed

from each plant in eachfrom each plant in each

generationgeneration

Select superior lineSelect superior line

after /


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0&0& "apid generation advance 9%; generationsQyr"apid generation advance 9%; generationsQyr

9&9& "e+uires less space,time and resources in"e+uires less space,time and resources in

early stages, therefore accommodates higherearly stages, therefore accommodates higher

O crossesO crosses

:&:& Superior to bul'Qmass selection if the desiredSuperior to bul'Qmass selection if the desired

genotype is at a competitive disadvantagegenotype is at a competitive disadvantage

natural selection usually has little impact onnatural selection usually has little impact on

population&population&

;&;& 7elayed selection eliminated confusing e.ects7elayed selection eliminated confusing e.ects

of hetero1ygosity more e.ective thanof hetero1ygosity more e.ective than

pedigree breeding when dealing with low hpedigree breeding when dealing with low h99

traitstraits


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0&0& ay carry inferior material forwarday carry inferior material forward

9&9& /ewer eld evaluations, so you lose the/ewer eld evaluations, so you lose the

advantage of natural selectionadvantage of natural selection

:&:& Aeed appropriate facilities to allowAeed appropriate facilities to allow

controlled environment manipulation ofcontrolled environment manipulation of

plants for rapid seed production cyclesplants for rapid seed production cycles

(day length, moisture and nutrient(day length, moisture and nutrient

control)control)


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BackcrossBackcross


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Same form whether self or crossSame form whether self or cross

pollinated speciespollinated species

$nly di.erence is pollination control$nly di.erence is pollination control

Kith bac'cross we approachKith bac'cross we approach

homo1ygosity at the same rate as withhomo1ygosity at the same rate as with

selngselng

8oal is to move 0 to a few traits from a8oal is to move 0 to a few traits from a

donor parent (decient in other traits)donor parent (decient in other traits)

BackcrossBackcross


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B '


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=imited use of BC to create a population=imited use of BC to create a populationfor selection that fosters wider geneticfor selection that fosters wider genetic

variance and modest introgression is avariance and modest introgression is a

separate issue than a repeated BC toseparate issue than a repeated BC to

derive a new cultivarderive a new cultivar >ensen suggested that a :%way (a >ensen suggested that a :%way (a

bac'cross to another recurrent orbac'cross to another recurrent or

superior parent following he single crosssuperior parent following he single crossof a desirable and an undesirableof a desirable and an undesirable

parent) was superior to single crossparent) was superior to single cross

followed by pedigree or other selectionfollowed by pedigree or other selection

methodologymethodology

Bac'crossBac'cross


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BC must be used with other, moreBC must be used with other, moree-ploratory procedures otherwisee-ploratory procedures otherwise 88ssR@R@

ust have a suitable recurrent parentust have a suitable recurrent parent

O of BCs to ma'e usually ;O of BCs to ma'e usually ; Dse several "P plants K2Dse several "P plants K2

#o incorporate T 0 trait, use parallel#o incorporate T 0 trait, use parallel

programs and then convergeprograms and then converge valuation phase can be less stringentvaluation phase can be less stringent

because you should already 'now thebecause you should already 'now the

utility of the recurrent parentutility of the recurrent parent

BackcrossBackcross


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Bac'cross BreedingBac'cross Breeding

"ecovery of the recurrent parent"ecovery of the recurrent parentgenotype follows this pattern!genotype follows this pattern!

recurrent recurrent donor donor

//00 3@3@ 3@3@BCBC00 M3M3 9393

BCBC99 4M&34M&3 09&309&3

BCBC:: ?:&M?:&M

Breeding Self-polinated Crops

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