AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

38

TREEIMPROVEMENT

BREEDINGWILTRESISTANCEINKOA

RichardA.Sniezko,Ph.D. (USDAForestService,DorenaGeneticResourceCenter),

NickDudley(Hawai‘iAgricultureResearchCenter),TylerJones(Hawai‘iAgriculture

ResearchCenter),andPhilCannon,Ph.D.(USDAForestService,PacificSouthwest

Region,ForestHealthandProtection)

PaperTitle:Koawiltresistanceandkoagenetics–keytosuccessfulrestorationand

reforestationofkoa(Acaciakoa)

Koaisaveryimportanttreespeciesecologically,economicallyandculturallyinHawai‘iandthereis

ahugedemandforplantingdegradedlandswithkoa.However,thehighsusceptibilityofkoatoa

wiltdisease,causedbytheFusariumoxysporumfungus,hasmademanylandmanagerscautious

aboutplantingthisspecies.Intheearly2000’saneffortwasbeguntoexaminekoaandthework

neededtomeettheshort,mid-andlong-termneedsfortherestorationofkoaforestecosystems

andthedevelopmentofcommercialkoaplantations.Obviouslydevelopingawaytominimizethe

impactsoftheF.oxysporumwiltwouldbenecessaryiftheseinitiativesweretobesuccessful.

Oneofthemostimportantdefensemechanismstoadiseasecausedbyanyfungusisgenetic

resistance.Theverylargedifferencesnotedinsurvival(4.0to91.6%,48monthsafterplanting)ofa

koaseedsourcefieldtrialplantedin1999atHARC’sMaunawiliResearchStationprovideduswith

anindicationthatwewouldbeabletofindthegeneticresistancetokoawiltneededforfuture

restorationandreforestationneeds.In2003,NickDudleyandRichardSniezkooutlinedalong-

termstrategyforexploringandutilizinggeneticresistancetokoa,includingintegratingother

componentsoftreeimprovementsuchasthedevelopmentofseedzones.Theprogramwas

patternedafterdiseaseresistanceprogramswithothertreespeciesthatwerealreadybeing

conductedbytheUSDAForestService’sPacificNorthwestRegion.Overthesucceedingyears,acore

teamofscientistsandforesterswereutilizedtoimplementdifferentphasesofthestrategyandto

refineitfurther(Dudleyetal.2012,2015,2017).

AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

39

Afirststepinthekoaresistance

programwastodevelopa

systemtorapidlyscreenkoa

treesfortheirgeneticresistance

tokoawilt.Thiswas

accomplished,usingyoung

seedlingsofindividualkoa

parenttreesandsubjecting

themtoinoculumofFusarium

oxysporum.Inthefirst

resistancetrial,in2007,the

seedlingprogenyofdifferent

parenttreesvariedinmortality

from4.2to91.7%,90daysafter

seedlinginoculation.By2016,

theprogenyofnearly600parent

treesfromvariouskoa

populationshadbeenevaluated

fortheirgeneticresistanceand

survivalrangedfrom0to96%,

(withmeansurvival~38.5%).

Furtherscreeningisunderway.

Fieldtrialshavealsobeen

establishedtoconfirmtheresultsoftheseedlingassayandtomonitorthedurabilityof

resistance(Figure1).Initialresultsareveryencouragingastheyshowthatseedlingsfrom

parenttreesscoredas“resistant”commonlysurviveinthefieldatratesof70%orgreater

throughyear3(Figure2)(Dudleyetal.2012,2015,2017).

Figure1:Highsurviving,highgrowthSeedlot#4in1999

koaprogenytestatMaunawili(8/2013)

AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

40

Tohelptothediverseenvironmentsfoundin

Hawai‘i,provisionalseedzoneshavebeen

devisedandthefirstseedorchardshavebeen

developed(Dudleyetal.2012,2015,2017).

Thegoalistobeabletoprovidelandmanagers

withseedthatwillproduceseedlingswithkoa

wiltresistancethatissuitedfortheareasthey

areinterestedinplantingwhilestillmaintaining

sufficientgeneticdiversitytobufferagainst

otheranyfutureabioticorbioticthreatstothe

species.Inthecaseofkoa,geneticresistanceto

koawiltwasthefirstkeytraittoevaluateand

incorporate,butongoingtreeimprovement

effortsarebeingmadetoincorporategrowthand

woodqualitycomponentsaswell.Theobjective

continuestobetodevelopgeneticallydiverse

andadaptablepopulationsofkoatomeetthe

long-termrestorationandreforestationneedsofHawai’iandtomakethisseedavailabletoallland

managers.

Needsforthefutureincludeestablishmentofmorefieldtrialsandorchards,additionalseed

collectionsfromtreesinnaturalstandstotestforresistance,thecontinueddevelopmentofseed

orchardsproducingkoawiltresistantseed,andtheselectionforothertraitsofimportanceinkoa

(eggrowthrate,formandwoodquality).Needsalsoincludebasicresearchonkoatosupporttree

improvementeffortsandincludeimprovingseedproductionlevelsinseedorchardsandeven

betternurseryandsilviculturepractices(Figures3and4).Thekoawiltresistanceprogramhas

madesubstantialprogressinarelativelyshortperiodoftime.Partnersandcooperatorswill

continuetobeofkeyimportanceastheprogramadvances.

Additionalinformationonprogressonthekoaresistanceprogramcanbefollowedatthefollowing

websites:

https://www.ctahr.hawaii.edu/forestry/disease/koa_wilt.html

http://www.harc-hspa.com/forestry.html

Figure2:Koafieldtrialbeingplantedon

Oahuin2012.Thesusceptiblefamilynow

has0%survival,whiletheresistantfamilies

have70%survival.

AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

41

Figure3:Arange-widecollectionofA.koaseed

Figure4:Morphologicalvariationinpodsandphyllodes

AcaciakoainHawai‘i:FacingtheFutureProceedingsofthe2016Symposium,Hilo,HI:www.TropHTIRC.org,www.ctahr.hawaii.edu/forestry

42

Acknowledgements

MajorFundingProvidedby:USDA-ForestService-FHP,S&PForestry,USDA-NRCS,MauiCounty

Dept.ofWaterSupply.FredBell(USDAFS,retired)helpedprovidetheimpetusin2003tobring

USFSgeneticistandHARCpersonneltogethertoworkondevelopingresistancetokoawilt.

Cooperatorsandpartnersinclude:AileenYeh–HARC,USFSPSWResearchStation(JessicaWright,

ChristinaLiang),USFSRegion6(BrockMayo),VolcanoNationalPark,StateofHawai‘iDLNR-

DOFAW,HI-DepartmentofAgriculture,HI-DepartmentofTransportation,HI-Departmentof

HawaiianHomelands,UniversityofHawai’i:CTAHR,Hawai’iCountyR&D,OahuRC&D,Plant

DiseaseConsultingNorthwest,ForestManagementConsultants-Hawai’i,HaleakalaRanch,Wung

Ranch,ParkerRanch,KualoaRanch,KapapalaRanch,UlupalakuaRanch,MauiLandandPineapple,

Hawai’iReservesInc.,KamehamehaSchools,QueenEmmaFoundation,TheNatureConservancy,

LeewardHaleakalaWatershedPartnership,RenewableResources,andLBDorcyTrust.

LiteratureCited

DudleyN,JamesR,SniezkoR,CannonP,YehA,JonesT,Kaufmann(2012)Operationaldisease

screeningprogramforresistancetowiltinAcaciakoainHawai‘i.pp286-289.In:Sniezko,Richard

A.;Yanchuk,AlvinD.;Kliejunas,JohnT.;Palmieri,KatharineM.;Alexander,JaniceM.;Frankel,Susan

J.,tech.coords.2012.Proceedingsofthefourthinternationalworkshoponthegeneticsofhost-

parasiteinteractionsinforestry:Diseaseandinsectresistanceinforesttrees.Gen.Tech.Rep.PSW-

GTR-240.Albany,CA:PacificSouthwestResearchStation,ForestService,U.S.Departmentof

Agriculture.372p.

DudleyNS,Jones,TC,JamesRL,SniezkoRA,CannonP,BorthakurD(2015)Applieddisease

screeningandselectionprogramforresistancetovascularwiltinHawaiianAcaciakoa.Southern

Forests:aJournalofForestScience,77(1):65-73.doi:10.2989/20702620.2015.1007263

DudleyN,JonesT,JamesR,SniezkoR,WrightJ,LiangC,GuggerPF,CannonP(2017,inpress)

AppliedgeneticconservationofHawaiianAcaciakoa:aneco-regionalapproach.In:Sniezko,

RichardA.;Man,Gary;Hipkins,Valerie;Woeste,Keith;Gwaze,David;Kliejunas,JohnT.;McTeague,

BriannaA.,tech.cords.2017.Geneconservationoftreespecies–bankingonthefuture.Proceedings

ofaworkshop.Gen.Tech.Rep.PNW-GTR-xxx.Portland,OR:U.S.DepartmentofAgriculture,Forest

Service,PacificNorthwestResearchStation.