PRINCIPLES OF CROP PRODUCTION

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1. PRINCIPLES OF CROP PRODUCTION
ABT-320
(3 CREDIT HOURS)
LECTURE 7
SELECTION IN CROSS-POLLINATING CROPS
SELECTION IN SEGREGATING POPULATION

10. SELECTION IN CROSS-POLLINATING
CROPS
Selectionisappliedincross-pollinatedspeciesforpopulationimprovement.
Themethodsofselectionusedinthecaseofcross-pollinatedcropsare:
1.MassSelection
2.RecurrentSelection

11. MASS SELECTION
Massselectionisthetechniqueinwhichindividualplantsareselected
onthebasisoftheirperformanceandthebulkedseedsareusedto
producethenextgeneration.Sincephenotypeisthesolecriterionof
selectioninmassselection,itsefficiencydependsonthemagnitudeof
heritability.Severalmodificationsofmassselectionarealsobeing
practiced:
•SelfedPlantMassSelection
•ProgenySelection

12. SELFED PLANT MASS SELECTION
Theavailableadditiveanddominantgenevarianceinarandommating
populationcanbereshuffledthroughselfing.Theselfedprogenyrows
areselectedonthebasisofphenotypicperformance.Theyarepollinated
byarandombulkofotherS
1plants.Theunitofselectionand
recombinationarethusselfedS
1plants.

13. PROGENY SELECTION
•Thisismassselectionwithprogenytest.Thesimplestformofprogeny
selectionistheear-to-rowmethodinwhichanumberofplantsareselected
onthebasisofthephenotypeinthefirstseason.Theyareallowedtoopen
pollinateandtheseedsfromindividualplantsareharvestedseparately.Inthe
secondseason,progenyrowsaregrownfromeachselectedplant.Theprogeny
rowsareevaluatedfordesirablecharactersandsuperiorprogeniesare
identified.Theyarepermittedtoopenpollinateandtheprogenyisgrownin
progenyrowsagain.Thecycleisrepeatedandfinallytheseedsofsuperior
plantsarecollectedandbulked.
•Inprogenyselection,theselectionismadeonthebasisofprogenytestand
notonthephenotypeofindividualplants.Thishelpsintheselectionofplants
withbettergenotypes.Thisisagoodtooltoincreasetheyieldingabilityof
openpollinatedplants.
•Thelimitationinmostoftheprogenyselectionschemesisthatthereisno
controlonpollinationandtheplantsareallowedtoopenpollinate.Besides,
selectionisbasedonthematernalparentonlywhichreducestheefficiencyof
selection.

14. RECURRENT SELECTION
Recurrentselectionisdefinedasreselectiongenerationaftergeneration
withinterbreedingoftheselectedplantstoprovideforgenetic
recombination.
Thisisatechniqueofselectioninwhichoneoriginalselectioncycleand
oneormorerecurrentselectioncyclesarecarriedoutforpopulation
improvement.Intheoriginalselectionscycle,anumberofplantswith
desirablecharactersareselectedandself-pollinated.Separateprogeny
rowsaregrownfromtheselectedplantsinthenextgeneration.The
progeniesareintercrossedinallpossiblecombinationsandequal
amountofseedsfromeachiscompositedtoproducethenext
generation.

15. SELECTION IN SEGREGATING
POPULATIONS
PopulationslikeF
2,F
3etcarecalledsegregatingpopulations.Techniques
ofselectionlikemassselectionandpurelineselectioncannotbeapplied
tosuchpopulations.Themethodsofselectiongenerallyusedinthecase
ofsegregatingpopulationsarepedigreemethod,bulkmethodandsingle
seeddescentmethod.

17. PEDIGREE METHOD
•Inthismethodofselection,individualplantsareselectedinF
2
generationandsubsequentgenerationsbasedontheprogenytest.
Duringtheentireoperation,apedigreerecordoftheparentsand
progenyismaintained.Individualplantselectioniscontinuedtillthe
progeniesshownosegregation.Atthisstage,selectionisdoneamong
theprogeniesbecausetherewouldbenovariationwithinprogenies.
•PedigreeRecord:Adetailedrecordoftherelationshipbetweenthe
selectedparentsandtheirprogeniescanbecalledtheirpedigreerecord.
Pedigreecanbedefinedasadescriptionoftheancestorofanindividual
anditgenerallygoesbacktoitsdistantancestor.

18. PROCEDURE OF PREDIGREE METHOD
Pedigreemethodofselectionisanefficientmethodofhandling
segregatinggenerations.Thestepsinvolvedareexplainedinthecoming
slides.

19. F
1GENERATION
TheF
1plantsaregrowntoproducesufficientF
2seeds.TheF
1plantsare
plantedandassessedfortheirbehaviorwithregardtoeasilyobservable
charactersandtheselfedplantsthatoccuraccidentallyareidentified
andremoved.

20. F
2GENERATION
Itisthemostimportantgenerationthatshowsmaximumgeneticvariation
andprovidestheopportunitytoselectindividualplants.Arelativelylarge
numberofplantsareraisedandevaluated.Selectionofplantsismadebased
ontheirbehavior.Theselectedplantsareindividuallyharvestedanda
detailedrecordiskeptwithrespecttogeneticidentityoftheplantsandtheir
agronomiccharacters.

21. F
3GENERATION
TheprogenyrowsoftheselectedF
2plantsaregrownalongwithcheck
varietyintheF
3.Theplantsareliberallyevaluatedandcomparedvisually
withcheckvarieties.Thepromisingindividualplantsareselectedwithin
theretainedprogenies.Itmustbeensuredthatprogenieswith
susceptibilitytodiseasesandpestsarerejected.Plantsareindividually
harvestedandarecordofgeneticandagronomiccharactersiskept.

22. F
4GENERATION
TheprogenyofselectedF
3plantsisgrowntoproduceF
4families.The
progenyofoneF
3plantconstitutesafamily.Thefamilydifferences
becomeobviousinthisgenerationandthenumberoffamiliescanbe
reducedbyvisualselection.TherejectionofsomeF
4familiesisneededif
theyshowsomeprominentundesirablecharacteristics.

23. F
5GENERATION
Inthisgeneration,theselectedplantsaregrowninprogenyrowsusually
inlargenumbers.Bythisgeneration,variationwithinfamilies
considerablydecreases.Progeniesorevenfamiliesshowingappreciable
planttoplantvariationsarerejectedtosetasidethechanceofselecting
hybridplants.Theselectedfamiliesarebulkharvested.

24. F
6-F
8GENERATIONS
Preliminaryyieldtrialsoftheselectedfamiliesarecarriedoutatthis
stage.Screeningforresistanceandqualityisalsodone.

25. F
7-F
10/F
12GENERATIONS
Multilocationtrialsareconductedatthisstage.Screeningforresistance
andqualityiscarriedout.

26. VARIETY RELEASE & SEED
MULTIPLICATION
Whentheabovestepsareaccomplished,theselectedfamiliesare
releasedasnewvarieties.Thesenewvarietiesaremultipliedand
distributedtofarmers.

27. MERITS AND LIMITATIONS OF PEDIGREE
METHOD
Pedigreemethodprovidesthemaximumopportunitytothebreederto
exercisehisskilltoselectplantswiththemostdesirablegene
combinationsandithelpstoevaluatetheselectionsfortheir
performanceoveralargenumberofyears.Atthefinalstageofbulking,
thepedigreerecordhelpstobulkprogenieswithsimilaryieldpotential.
But,itisalaboriousanddemandingmethodintermsofresourcesand
time.Itinvolvesextensivedatarecording.Thematerialistobeevaluated
onlyunderoptimalenvironmentalconditionswhichmakesoff-season
operationsimpossible.

28. SINGLE SEED DESCENT METHOD
Thisisamodificationofpedigreemethod.Thisenvisagescomplete
exclusionofselectionamongorwithinlinesuntilsufficienthomozygosity
isattainedbytheF
5orF
6generation.Here,alargenumberofF
2plants
arecarriedforwardbymaintainingtheirlineagethroughsingleseed
fromeachplanttilltheF
6generation.Theseedsofthesingleplantsare
thengrowninprogenyrowsfortheirmultiplicationandtrials.

30. BULK METHOD
Thebulkmethodisashort-termandlabor-savingprocedureforthe
managementofsegregatinggenerations.Thistechniqueisadoptedto
attainsufficientlevelofhomozygositypriortotheinitiationofindividual
plantselection.TheseedsareharvestedinbulkfromF
2toF
4orF
6
generationandindividualplantselectionispracticedonlyafterwards.

32. PROCEDURE OF BULK METHOD
1.F
1Generation:TheF
1plantsaregrownalongwiththeparentsandthe
selfedprogeny,ifany,isremoved.SufficientF
2seedsareharvested.
2.F
2toF
4Generations:sufficientnumberofF
2plantsaregrownand
harvestedinbulk.Acompositesampleofharvestedseedsarecollected.
TheprocessisrepeatedintheF
3andF
4generations.F
5seedsare
harvested.
3.F
5Generation:ThebulkedF
5seedsareplantedanddesirableplantsare
selected.Eachselectedplantisharvestedseparately.
4.F
6Generation:Singleplantprogenyrowsaregrown,uniformand
promisingprogeniesselectedandtheselectedprogeniesarebulk
harvestedseparately.
5.F
7-F
9Generations:Preliminaryyieldtrialsareconductedtoreducethe
numberofF
7progenies.Testsarerepeatedatdifferentlocationsinthe
nextgeneration.InF
9generation,thelastprogenylineisselectedand
releasedasanewvariety.

33. MERITS & LIMITATIONS OF BULK
METHOD
Thismethodiscomparativelyinexpensiveandeasy.Selectionstartsata
stagewhenthepopulationattainshomozygosity.Singleplantselectionis
donewhentheplants(F
5orF
6)areuniformingeneral.Thepopulationis
expectedtoimproveforintangiblecharacterslikeadaptationtoexisting
environment.Thereisachancethatalargeproportionofundesirable
materialiscarriedforward.

34. THE END