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EARLYSELECTIONFORVOLUMEGROWTHINSLASHPINE By SCOTTEDWARDSURLES ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 1993 ACKNOWLEDGEMENTS SeveralyearsagomymajorprofessorDr.TimothyWhite,andDr.MaryDuryeamade plansforinitiatingalarge-scaleearlyselectionproject. Withsubstantialcontributionsfromthem andmanyotherpeople, Ihavecarriedouttheproject. Timhasbeenatrulygreatmajor professor. Hehassharedhistime,knowledge,andfriendshipwithme;hetakesverygoodcare ofhisgraduatestudents. Dr.GaryHodgehasbeenmystatisticsmentoroverthepastfouryears aswellasservingasacommitteememberandIamsincerelygratefultohimforhisguidanceand friendshipaswell. IalsoamgratefultoDr.MaryDuryea,Dr.AlanLong,andDr.JerrySartain forservingonmycommittee. Dr.Longwasalsoinstrumentalinconstructingtheirrigation system. Mr. GregPowellalsodeservesspecialrecognitionforhelpingmeinthedaytoday operations. Ofcourse,IcannotforgetCharlesAkinswhohassinceretired, butwasvery instrumentalinbuildingtheseedlingboxesandtakingcareoftheseedlingsduringtheearlydays ofthisproject. IwanttothankcurrentandformerstaffmembersattheAustin-CaryForestwho helpedwithseedlingboxconstructionandharvesting:MikeAllen,SteveBrooker,GaryDurden, EddieHiggins,andSamJones. Ialsowanttothankthethreeladieswhodidmostofthe 'grunt'workinthisstudyseparatingbiomasscomponents(needleandrootpicking),GinaTaylor, JenniferPrentiss,andChristyLovejoy. Finally,Ithankmyfellowgraduatestudentswhofreely and willinglygave a helping hand: Delaney Faircloth, Dudley Huber, Kris Irwin, Carol McCormac-Wild,DeborahMcGrath,MikeO'Donnell,KenSmith,AnneTodd-Bockarie,andthe departmenttechnicians:RobertBerger,JeffEnglish,AbbieFoxx,HarmKok,andWinnieLant. ii IgratefullyacknowledgethemembersoftheCooperativeForestGeneticsResearch Program(CFGRP)andtheGeorgiaForestryCommissionforfundingthisproject. Ihavetruly enjoyedworkingwithTim,Mary,Gary,Greg,andthestudentsoverthepastfouryearsatUF. TABLEOFCONTENTS ACKNOWLEDGEMENTS ii ABSTRACT vi INTRODUCTION 1 RELATIONSHIPSAMONGSEEDWEIGHTCOMPONENTS, SEEDLINGGROWTHTRAITSANDPREDICTED FIELDVALUESFORVOLUMEINSLASHPINE 5 Introduction 5 MaterialsandMethods 7 ResultsandDiscussion 10 GENETICPARAMETERESTIMATESFORSEEDLINGDRYWEIGHT TRAITSANDTHEIRRELATIONSHIPWITHPREDICTED FIELDBREEDINGVALUESFORVOLUMEINSLASHPINE 22 Introduction 22 MaterialsandMethods 24 ResultsandDiscussion 28 INDIRECTPREDICTIONOFBREEDINGVALUESFOR VOLUMEGROWTHUSINGSEEDLINGGROWTHTRAITS 48 Introduction 48 MaterialsandMethods 50 ResultsandDiscussion 56 CONCLUSIONS 70 APPENDIXA.VARIANCEOFFAMILYMEANSOFTHE NINEMOSTPROMISINGTRAITS 73 APPENDIXB.FAMILYMEANCORRELATIONSAMONG THENINEMOSTPROMISINGTRAITS 74 iv REFERENCELIST 75 BIOGRAPHICALSKETCH 81 v AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulfillmentofthe RequirementsfortheDegreeofDoctorofPhilosophy EARLYSELECTIONFORVOLUMEGROWTHINSLASHPINE By SCOTTEDWARDSURLES August1993 Chairperson:Dr.TimothyL.White MajorDepartment:ForestResourcesandConservation Thisstudywasconductedtoinvestigateearlyselectionfor15-yearvolumegrowthin slashpine.Seedlingsfrom64open-pollinatedfamiliesofslashpineweregrownunderlowand highnitrogen(N)treatments(5ppmand50ppm)inoutdoorboxesfortwogrowingseasons. These families have been extensively tested for 15-year volume growth in the field. Approximately 360seedlingtraits were measured orderivedusingdata from several non- destructivemeasurementsandfromdestructiveharvestsconductedat3,6, 10,and18months aftersowing. Thefirstpartofthisstudyinvestigatedrelationshipsbetweenseedweightcomponentsand seedling growth, and 15-year volume growth. Embryo weight consistentlyhad a strong relationshipwithbothseedlinggrowthtraitsand15-yearvolumegrowth,andmaybeusefulas anearlyselectiontrait. Duetothestronggeneticrelationshipbetweenseedweightcomponents andseedlinggrowth,statisticaladjustmentsforseedweighteffectsinslashpinemightremove usefulgeneticvariationratherthanremovetemporarymaternaleffects. vi Inthesecondpartofthisstudy,geneticparameters(i.e.,familyheritabilities,typeA geneticcorrelations,andtypeBgeneticcorrelations)wereestimatedfordryweighttraits(i.e., needle, stem, taproot, lateral roots) measuredat3, 6, and 10months. Familyheritability estimateswerehighforalltraitsinallharvests(h,2 > 0.70). TypeAgeneticcorrelations, measuringthegeneticsimilaritybetweenpairsoftraitsinthesameNtreatment,indicatedthat dryweighttraitshavestronggeneticrelationships. TypeBgeneticcorrelations,measuringthe geneticsimilarityofthesametraitacrossthetwoNtreatments,alsoindicatedstronggenetic relationshipsbetweentraits. Inthethirdpartofthisstudy,selectionindicesweredevelopedfromover360seedling traitstoestimatetheefficiencyofearlyselectioninslashpine. Comparedtodirectselectionfor 15-yearvolumegrowth,someselectionindicesweremorethan60%efficient.Selectionindices weremoreefficientatpredictingthebottom25%ofthepopulationthanthetop25%.Anearly selectiontechniqueusingtraitsinthisstudywouldnotbeefficientenoughtosupplantprogeny testingbutcouldbeusedtoreducethesizeoffieldtestsviaearlycullingofpoorperforming familiesortoprovideinformationfordirectedcrossingamongparents. vii INTRODUCTION TheUniversityofFlorida'sCooperativeForestGeneticsResearchProgram(CFGRP) isacooperativeoftheuniversityand11forestindustrycorporationsandstateforestryagencies workingtogeneticallyimproveslashpine. Collectively,themembersownorbreedforover20 millionacresofcommercialtimberlandinFlorida,Georgia,Alabama,andMississippi. Two majorgoalsoftheCFGRParetoidentifyandproducegeneticallyimprovedvarietiesofslash pineforreforestationandtoconductresearchthatincreasesourknowledgeofthegeneticsof slashpine. Towardsthesegoals,duringtheearly1960s,theCFGRPselectedover2,000slashpine treesfromnaturalpinestandsbasedontheirphenotypicappearance. Duetolargeenvironmental effects(suchasmicrositedifferencesinsoil,competition,localizedinbreeding,andotherstand- to-standvariations),theirphenotypicappearancepoorlyreflectedtheirgeneticpotential(i.e.,low heritability). Therefore,theirprogenyweregrownonmanydifferentsites(fieldorprogeny testing)withproperexperimentaldesignstofacilitateselectionbasedongeneticquality. In this first generation ofimprovement, over 300 field tests were established and measuredseveraltimesuntilage15atasubstantialcost. Currently,thebreedinggeneration intervalintheCFGRPisapproximately13-15years;evaluationforparentalworthisatage8-10 and breedingprocedures add another 5 years (White and Hodge 1993). Consideringthe resourcesspentinmaintaininglargenumbersoffieldtestsforlongperiods,itisveryimportant toidentifytraitsearlyinthetree'slifecycletofacilitateearliergeneticevaluationorreduction oftestsizes. Iftraitscanbefoundinseedlingsatoneortwoyearsofagethatarepredictiveof 1 2 latertreegrowthinoperationalfieldenvironments,thenthiscouldbothreducecosts(byreducing sizeand/ornumberoffieldtests)andincreasegeneticgains(byallowingearlierselectionand thereforemorerapidturnoverofgenerations). TheCFGRPhasselected933second-generation genotypesofslashpinewhichwillrequirefieldtestingbeginningin 1995. Unlessanearly selectionprocedurecanbedevelopedforslashpinebythattime,evaluationoftheseselections mayrequireamountsofresourcescomparabletothefirstgenerationofimprovement. Mosttreeimprovementprogramsforconiferspecieshaveinvestigatedthefeasibilityof earlygeneticevaluation. Avastmajorityofstudieshavehadlimitedsuccess;theresultshave notbeenconclusiveenoughtowarrantoperationalearlyselection. Therearenumerousreasons forthefailureofearlyselectionstudies,butIwillfocusonthefourmainproblems. First,a largenumberoffamiliesandindividualsarecriticalforaccuratepredictionofjuvenile-mature correlations(Lambeth1983). Testingafewfamiliesand/orafewseedlingsperfamilymayyield impreciseestimatesofjuvenile-maturecorrelations. Forreliableestimatesofgeneticparameters, manyfamilies(50ormore)arerequired(Huberetal.1992). Second,whencalculatingjuvenile- maturecorrelations,manystudies(particularlyearlierstudies)haveusedimpreciseestimates of thematuretraitratherthanpreciselyestimatedadditivegeneticbreedingvaluesderivedfrom testingacrossmanyfieldsites. Third, moststudieshavenotaddressedseedeffects whichmayhaveaconfounding influence on the genetic analysis ofearly seedling growth leading to biased estimates of heritabilitiesandgeneticcorrelations(Lambeth1983,St.ClairandAdams1991). Fourth,choice ofseedlinggrowingenvironmentiscriticaltomaximizethepredictiveabilityandsomebelieve thatseedlingenvironmentsshouldsimulatenaturalconditions(WaxierandvanBuijtenen1981, Williams1988). 3 Finally,genophenotypicorfamilymeancorrelationswiththetargettraitshavebeen estimatedforsinglejuveniletraits. Multiple-traitselectionindicescombiningseveraljuvenile traitswilllikelyprovidebetterpredictiveabilityforthematuretraitthansingle-traitcorrelations (Foster 1986), particularly if the juvenile traits are correlated with the target, but not phenotypicallycorrelatedwitheachother(WhiteandHodge1991). Inthisstudy,attemptsweremadetocircumventsomeoftheseproblemsbya)usinga largenumberoffamilies (64)whichhavealreadybeenextensivelyfieldtestedforvolume growth,b)usingbestlinearpredictiontomakeprecisepredictionsoftheparentalbreedingvalues forfieldvolumegrowth(WhiteandHodge 1988), c)growingtheseedlingsintwodistinct nitrogen(N)environmentsknowntoalterseedlingtraitexpressionandsimulatenaturalconditions (DeWaldetal. 1992),d)analyzingcombinationsoftwo-andthree-traitselectionindicesto predictfieldbreedingvaluesande)addressingtheeffectsofseedweightsonearlyselectiontraits andfieldbreedingvalues. Thefirstchapterfocusesontheeffectsofseedweightcharacteristicsonseedlinggrowth andlong-termfieldgrowth. Thegoalswere 1)toexaminerelationshipsamongseedweight components and seed size classes, 2) to estimate the magnitude ofseed size effects and germinationvigoronthreekeyseedlinggrowthtraitsduringthefirsttwogrowingseasons,and 3)toevaluateseedweightcomponentsaspotentialgeneticselectioncriteriaforpredicting5-and 15-yearvolumegrowth. Thesecondchapterfocusesongeneticparametersestimatesofseedlingdryweights. The goalswere1)toestimatefamilyheritabilityforseedlingdryweighttraitsinlimiting(simulating naturalconditions)andnon-limitingNtreatments,2)toestimategeneticcorrelationsamongthe traits,and3)toevaluatealltraitssinglyandinallpossiblecombinations(acrossthreedifferent harvestdatesandtwoNlevels)topredict15-yearbreedingvaluesforvolumegrowth.