Date post: | 10-Oct-2015 |
Category: |
Documents |
Upload: | organic-farming-research-foundation-ofrf |
View: | 20 times |
Download: | 0 times |
of 16
How to Breed Carrots for Organic Agriculture www.seedalliance.org
How to Breed Carrotsfor Organic Agriculture
Organic Seed AllianceAdvancing the ethical development and stewardship of the genetic resources of agricultural seedPO Box 772, Port Townsend, WA 98368
This publication was made possible through a grant from Organic Farming Research Foundation and Seed Matters
How to Breed Carrots for Organic Agriculture www.seedalliance.org2
Section I: Introduction...................................................................................................................................................3 Section II: Introduction to Breeding........................................................................................................................3Section III: Breeding Goals...........................................................................................................................................3Section IV: Germplasm..................................................................................................................................................4
Section V: Reproductive Biology.................................................................................................................................4
Section VI: Plant Breeding............................................................................................................................................5 Matingsystemsforseedproduction................................................................................................................................5 Generatingbreedingpopulations.....................................................................................................................................5 Makingthecross-pollination................................................................................................................................7 Controlledpollination.............................................................................................................................................7 Straincross...................................................................................................................................................................7 Massselection.............................................................................................................................................................8 Familyselection.........................................................................................................................................................8 Breedingtimeline.....................................................................................................................................................................8 Breedingsummary................................................................................................................................................................11Glossary............................................................................................................................................................................13
References and Resources.........................................................................................................................................15
Table of Contents
How to Breed Carrots for Organic Agriculture www.seedalliance.org3
Carrotshavelongbeenanimportantfreshmarketcroparoundtheworld.Thebreadthofregionalpreferenceshasensuredthatawidevarietyoftypesandvarietiesexistacrossculturesthatusethisnutritionallyimportantvegetableasanev-erydaystapleoftheirdiet.Worldwide,therearedozensofdifferentmarkettypesofcarrots,eachwithhundredsofuniquevarietiesthathavebeenimportanttosomesegmentofthemarketoverthelastcentury.WhenEuropeancarrotswereimport-edtoNorthAmerica,theyweregrownprimar-ilyasafall-harvestedvegetable,storedthroughwinterandusedforcooking.Ascarrotsgainedpopularityasafreshmarketcropforallseasonsinearly20thcenturyAmerica,therewasaneedforbunchingcarrotssoldwiththeirtopsintact.Thisneeddemandedthinner,sleekrootedcarrotswithoutlargeshouldersthatpushtherootsapartatoddangleswhenbunched.Aneweraofinno-vationinplantbreedingdeliverednewtypesofcarrotsthatrepresentcombinationsofthediffer-enttypesfromaroundtheworld.Thisinnovationhasbeenheightenedinthelast20yearswiththereintroductionofolder,uniquelycoloredcarrotsintothemarketplace.
Acenturyago,carrotseedproductionandbreed-ingwasthedomainofseriouscarrotgrowersandthesmallregionalseedcompaniesthatwerethenorminNorthAmericaandinmanyplacesaroundtheworld.Bythemid-20thcentury,bothseedproductionandbreedingbecamemorespecialized,andmostcommercialfarmersinNorthAmericanolongerconsideredproducingtheirowncarrotseed.Thecommercialopen-pollinated(OP)car-rotvarietiesbredandmaintainedfromthe1920suntilwellintothe1970sweresuccessfulinsupply-ingthevariousneedsofboththefreshmarketandprocessedvegetabletrade.TheseedcompaniesgrowingthebeststrainsofthesevarietieswerequitecompetentatmaintainingaselectionofeachOPvarietywithahighdegreeofuniformity,whileavoidingthepitfallsofinbreedingbyselectingtoonarrowly.Withtheadventandsubsequentcom-mercialdominanceofhybridcarrotsbeginninginthe1970s,fewerseedprofessionalshadtheskills
toselectandmaintainhigh-qualityOPvarieties.
Thegoalofthismanualistoexplainsimplemeth-odsfordevelopinganOPcarrotvariety.WhilecarrotbreedingprogramsatlargeseedcompanieshavelargelyabandonedOPs,thereareanumberofreasonswhyOPsarebestsuitedtoservefarmerbreedersaswellasindependentseedcompaniesthataddressregionalneeds.BybreedinganOPvarietythatretainsadequategeneticvariabilitywhileselectingforuniformityforalloftheimpor-tantmarkettraits,itispossibletoproduceavari-etythatcansubsequentlybeselectedforthevariedclimatesandculturalneedsofdifferentregions.
Werecommendthatfarmerbreedersfirstdevelopbreedinggoals.InOrganicSeedAlliances(OSA)Introduction to On-Farm Organic Plant Breeding,weoutlinethegeneticconceptsofbreedingandprovidefarmerbreedersatemplateforbreedingcrops.Thesearethebasicstepsforbreedingcropsonyourfarm:
1.Developyourbreedinggoals
2.Identifyparentalmaterial,includingconductingtrialstofindthebestparents
3.Makecrosses
4.Selectandrecombineyourselectedbreedingmaterial
Thefirststepofanybreedingprojectistodevelopbreedinggoals.Belowisalistofthemostimpor-tanttraitsforcommercialcarrots,includingthefoliartraitsthatareparticularlyimportantfororganicgrowers.ThesetraitswillbediscussedfurtherintheSelectionsection.
Germination/strengthofemergenceSeedlingvigor
I. Introduction
*Definitionsfortechnicalwordsthatareitalicizedandboldedcanbefoundintheglossary
II. Introduction to Breeding
III. Breeding Goals
How to Breed Carrots for Organic Agriculture www.seedalliance.org
CanopydevelopmentandweedcompetitivenessMaturityslotTopattachmentDiseaseresistanceColorintensityCorecolorRootshapeRoottipfillFlavorSweetnessHarshnessStorability
Germplasmisacollectionofgeneticresourcesinaspecies,andistherawmaterialthataplantbreederusestodevelopnewvarieties.Breedersof-tenusethetermgermplasmtorefertosub-groupsoftheentiregermplasmthatexistsforacrop.Forinstance,carrotbreedersrefertothepurplecar-rotgermplasmortheAlternariablightresistantgermplasmasawaytospecifythecropsbreedingmaterialusedintheirwork.Whileabreederwillprobablyneverusemorethanafractionofthismaterialforbreedingpurposes,youshouldlearnasmuchaspossibleaboutavailablematerialthatincludestraitsthathelpyoumeetyourdesiredbreedingobjectives.However,nooneiseverfullyawareofallthegermplasmthatmaybeusefulforanyparticularbreedingproject,whichiswhylearningaboutthecropthatyouareinterestedinbreedingisalifelongpursuit.
Inthemodernworldwheremostofthenewercar-rotvarietiesareF1hybrids,plantbreedersshouldbeonthelookoutforgoodOPmaterial.ThereareafewcommonOPvarietiesstillcommerciallyavailableinNorthAmerica,andanumberofoldervarietiescanberequestedthroughtheGermplasmResourcesInformationNetwork(GRIN)oftheU.S.DepartmentofAgricultureorinheirloomseedcollections.Unfortunately,carrotshavealimitedgermplasmpoolcomparedtoothercommonvege-tablecropspecies,asbiennialrootcropsarehardertoreproducethanmostannualseedcrops.Also,ifOPcarrotvarietiesarenotmaintainedthroughdili-gentselectionwhenseedisincreased,theirpheno-typicconstitutionusuallydegeneratesrapidly.
Agoodbreedermustbeopentofindingcommer-cialOPvarietiesfromaroundtheworldthatarestillbeingactivelymaintained.Thisisoftenthemostvaluablebreedingmaterial,asitcanmostrapidlybedevelopedintonewvarieties.SomebreedershavealsousedF1hybridsforparentalmaterialintheirbreedingwork.Thedetailsofhybridcarrotbreedingarebeyondthescopeofthismanual,butnotethatF1hybridcarrotseedisproducedusingnaturallyoccurringcytoplasmic male sterility (CMS)inthefemaleparent.Seedcol-lectedfromF1progenyorsubsequentgenerationswillhavecytoplasmwiththesesterilityfactorsthatcouldresultinfuturesterilityproblems.There-fore,itmaybebesttostartabreedingprojectwithOPmaterial.Thatsaid,iftheprogenyfromanF1hybridvarietyexhibitsgoodfertilityintheF2andF3generations,theprogenyofthisexistingF1hy-bridlikelyhadplentyofnuclear restorer genestoadequatelyrestorethesterilityoftheCMS,andthematerialmaybeusedindevelopinganOPvariety.
Whileplantbreedingdiscussionsoftenbeginwithwhichparentsarebesttocross-pollinateforcre-atingabreedingpopulation,allbreedersshouldrememberthatthebreedingprocesssometimesbeginswithanalreadyexistingpopulationofthecrop.Inthissituation,breedersfindanexistingOPpopulationthathasadequategeneticvariationforthedesiredtraits,whichallowsthemtobypassthestepsofchoosingparentsandmakingacross.Therearealsocaseswhereabreederdiscoversadiversepopulationthathasoccurredduetoanun-intendedcrossinthefieldandrealizesthatitholdspromiseasabreedingpopulation.Thepointisthatgermplasmiswhereveryoufindit,andallgoodfarmersandplantbreederslearntorecognizegoodgermplasmforspecificbreedingneedsovertimeastheygainexperiencewiththecrop.
Carrotsareabiennialcross-pollinatedspeciesthatrelyoninsectpollination.Manyspeciesofpollinat-inginsectsareattractedtocarrotflowers,includingwasps,Syrphidflies(alsoknownashoverflies),wildbees,anddomesticbees.Flowersareborneonaseriesofcompoundumbels,startingwithasinglecentralinflorescence,knownastheprimaryor
IV. Germplasm
V. Reproductive Biology
How to Breed Carrots for Organic Agriculture www.seedalliance.org
kingumbel,followedbyafewsecondaryumbels,andthenmanymoretertiaryumbels.Inmostcli-mates,thebestseedisharvestedfromtheprimaryandsecondaryumbels,astheywillhavethelongestperiodoftimetofullymaturetheirseed.Themul-tiple-floweredumbeletsoneachcompoundumbelusuallyhaveatleastadozensmallperfectflowerswithfivestamens,fivepistils,andfivesepals.Theovaryofeachblossomhastwolocules,eachpro-ducingasingleseedwhensuccessfulfertilizationhasoccurred.Whilecarrotsarefullyself-fertile,amajorityoftheseedproducedisduetocross-pol-linationbetweenplantsinthepopulation.Muchofthiscross-pollinationisduetothefactthatcarrotsareprotandrous:theanthers onanyparticularflowershedpollenbeforethestigmaofthatsameflowerisreceptivetofertilization.Thisdecreasesthechancesofself-pollination,asinsectswillflyfromumbeltoumbelinanattempttofindmatureflowers.Protandryisanevolutionarymechanismtoenforceamajorityofcross-pollinationincar-rots,asthisspeciesismoresusceptibletopotentialinbreeding depressionfromexcessiveself-pollina-tionsthanmostagriculturalcrops.
Producingcarrotseedonthefarmisusuallydoneacrosstwoseasons,whichisnaturalforthecropwhengrowinginitsnativehabitat.Carrotrootsforplantbreedingpurposesareproducedduringonegrowingseason,andaredugupandevaluatedforrootcharacteristicsattheendofthefirstsea-son.Thesecarrotsshouldbeplantedlaterintheyear.Thatwaytherootsgrowtomarketablesizeaslateaspossibleattheendofthefirstseason,minimizingwinterstoragetime.Overwinteringcanalsobedoneinsitu,orinthefield,inmilderclimates,buttherootsmustbevernalizedinei-thercase.Aswithallbiennialcrops,carrotsneedtobevernalizedinordertoflower.Vernalizationisaprocesswherethebiennialplant(inthiscasethecarrotroot)isexposedtoatleast8to10cu-mulativeweeksoftemperaturesatapproximately50F(10C)orbelowbetweentheirfirstseasonofvegetativegrowthandtheirsecondseasonofre-productivegrowth.Thisisaccomplishedeitherbyallowingtherootstooverwinterinthegroundinregionswithmildwintersorbystoringtherootsatidealstorageconditions--35F(2C)and95%humidity--throughwintermonths.Thestepsforpreparingandstoringtherootsinacoldroom
arecoveredinPrinciples and Practices of Organic Carrot Seed Production in the Pacific Northwest,availableatwww.seedalliance.org.
Mating systems for seed productionTherearebasicallytwowaysthatcarrotvarietiesareproduced,eitherasopen-pollinatedvarietiesorasF1hybrids.Producingopen-pollinatedvariet-iesisrelativelyeasytodoifthegroweris(1)inaclimatesuitedtothereproductivephaseofcarrots,and(2)willingtoputinthetimetolearnthein-tricaciesofworkingwithabiennialseedcropandlearnthedisciplineofselectingforasetoftraitsinanOPwithoutoverlynarrowingthegeneticbaseofthepopulation.Producinghybridcarrotvarieties,ontheotherhand,requiresmaintainingaseriesofparentalinbredlines.Theseincludebothsterileandfertilemalelinesforeachfemaleparent,aswellasafertilemaleparentallineforeachhybrid.Toproducehybridseed,youmustfirstproduceseedofeachoftheparentlinesinseparateisolatedfieldsatleastayearbeforehybridproduction.Then,whenthehybridseedcropisproduced,thehybridseedisharvestedonlyfromthefemalepar-ent,asallofthemaleparentrowsaredestroyed.Thisprocessismuchmorecostlyandtime-con-sumingthanproducingOPseed,andisusuallyoutsideofwhatmostfarmerbreedersarewillingtodoinboththebreedingandtheproductionofacarrotvariety.
Generating breeding populationsAswithallbreedingprojects,youshouldchoosetherightparentstocrosstocreateaneffectivepopulationwiththepotentialofgeneratingprog-enywiththecombinationoftraitsyouareseeking.Thisrequiressomecareintheselectionofparentvarietiesorothergermplasmtofindorcreateausefulbreedingpopulation.Mostimportantly,thisprocessbeginswiththebreederhavingagoodworkingknowledgeofthetraitsinpotentialbreed-ingstocks.Identifyingthesetraitsrequiresgrow-ingfieldtrialsofexistingcarrotmaterialunderconditionsthataresimilartothoseusedbygrow-ers.Trialsneedtostartbeforethefirstcrossesaremadetoallowyoutoevaluateexistingmaterialforthetraitsyouhaveidentifiedasimportant(see
VI. Plant Breeding
How to Breed Carrots for Organic Agriculture www.seedalliance.org6
Selection).Tolearnmoreaboutconductingvarietytrials,refertoOSAsOn-farm Variety Trials: A Guide for Organic Vegetable, Herb, and Flower Producers,atwww.seedalliance.org.
Whengoodbreedingmaterialhasbeenidenti-fied,mostbreederswillmakeanumberofcrosses,incorporatingseveraldifferentcombinationsofthebestmaterialavailable.Initialcross-pollinationsareoftenmadeinagreenhousebetweensingleplantsinsmallmuslinorperforatedplasticpollina-tionpillowtubesthatcovertheflowersofthetwoplants.Insectpollinatorsmustbeintroducedintothesepollinationbags.Theseinsectsaretypicallyhousefliesorbluebottlefliesthatcanbepurchasedinthelarvalstage.Somesmall-scalebreedingprojectsusefeatherdustersintheeventthatfind-ingaflysourceisproblematic.Thedownsideofthissingle-plantbysingle-plantcrossingmethodisthatyouwillgetalimitedsampleofthegenesfromeachoftheparentalpopulations.Thisisbecausenooneplantinacross-pollinatedcropspeciesvarietycontainsallofthegeneticvariationpresentinthatvariety.Thismaynotbeaproblemincommercialhybridbreedingprogramswheremanycrossesaremadewiththeexpectationthatonlyafewwillresultinfinishedvarietiesorinbreds.However,
*IsolationtentscanbepurchasedfromRedwoodEmpireAwningatwww.redwoodempireawning.com.
Carrot crossing in outdoor pillow tubes: Initial single crosses can be made outdoors with homemade muslin fabric and small round metal frames that surround carrot flowers. Note the small black plastic tube with a cork on top where you can add fly larvae weekly that will hatch in the pillow tubes. Only seed produced inside of the pillow tubes is used for breeding.
Carrot pollination by flies: The common house fly and blue bottle fly are often reared and used by carrot breed-ers as they are effective pollinators.
House flies in carrot pillow tubes: For an isolated carrot pollination it is recommended that you use a high density of flies. Pillow tubes here are made from a perfo-rated plastic mesh used by cheese makers.
How to Breed Carrots for Organic Agriculture www.seedalliance.org7
mostfarmersarenotwillingtomanageanumberofcrosses.Inmostfarmer-ledbreedingprojects,thegoalisusuallytocreateafinishedvarietybyperformingonlyoneortwocrossesbetweentwowell-chosenparents.
Inordertocapturemoreofthegeneticvariationfromtheinitialcrossbetweenanytwoparents,werecommendatechniqueusedbyforagebreed-ersknownasastrain cross.Astraincrossisthecrossingoftwosmallpopulationsofthechosenparentvarieties.Tousethistechnique,selectanumberofcarrotrootsfromeachofthetwoparen-talpopulations.Theadvantageoffarmerbreedersusingastraincrossisthatbyusinganumberofse-lectedindividualsfromeachofthetwoparentsyouarecapturingagreaternumberofpossiblegeneticcombinationsfromtheoverallgeneticbreadthofbothparents.Straincrossescanbedoneinasmall,meshpollinationcageorinanopenfieldifisolatedfromotherfloweringcarrotsorferalQueenAnnesLace(Daucus carota),whichwillreadilycrosswithcultivatedcarrots.*Theadvantageofmakingastraincrossinanopenfieldisthatinmostloca-tionstherewillbeamplewildpollinators,nativewaspsandbees,toensureadequatepollination.
Making the cross-pollinationMakecertainthatcarrotrootshavebeenvernal-izedsothattheyflower.RefertotheReproductive Biologysectionaboveforinstructiononhowtovernalizecarrotroots.
Whenmakingacarrotcross,eitherbetweentwoplantsinapollinationpillowtubeorwithtwopar-entpopulationsinastraincross,labelthedifferentparentrootswithapedigreestake.Thatway,thecrossedseedthatresultscanbeharvestedsepa-ratelyfromthedifferentparents.
Controlled pollinationForasimplecrossbetweentwocarrotplantsfromdifferentvarieties,plantthetwoparentalrootsinseparatepotsinthegreenhouseorinthesoil(ifmakingthecrossinasmallpollinationtentorpillowtubeoutdoors).Astheplantssendoutflowerstalksandformflowers,coverthemwithacloth,plasticpollinationbag,ortent.Theseenclo-suresneedtobesecuredbeforethefirstflowersopenandarereceptivetopollination.Pollinat-
inginsectsmustnowbeintroduced.Housefliesandbluebottlefliesaremostcommonlyusedforthispurpose.Thelarvaeoftheseflyspeciesmustbeintroducedweeklyattheonsetofflowering,approximatelyahalf-teaspoonperpollinationbagortube.Theyusuallysurviveforoneweekinthesecages.Theseflieswillseekpollenandnec-tarandpollinatewiththeirmovementacrosstheflowers.Byaddingacottonballsoakedinsugarwatereverytwodays,thelifespanofthefliescanbeextendedbyseveraldays.Thismethodisusedextensivelybycommercialcarrotbreederswhomaymakehundredsofcrossesperyear.Pollina-tionenclosuresprovidetheadvantageofallowingyoutomakeanumberofcrossesinonelocationwithoutthethreatofcross-pollination.
Strain crossMostfarmerbreedersareunlikelytomakemorethanoneortwocrossesafteridentifyinggoodmaterialanddecidingonaspecificsetofbreed-inggoalsforadesiredphenotype.Thestraincrossmethodisoftenusedforasingle,isolatedcross.Inastraincrossofarootcroplikecarrots,selectatleast20to30ofthebestrootsfromeachofthetwoparentsandplantthemintwoseparaterows,sidebyside,withtheintentofharvesting,clean-ing,andbaggingtheseedasseparatelotsinthefirstyear.TheseedinlotAcontainsseedoftwodifferentconstitutions,withbothAxBandpureA(fromcrossesbetweenAplantsandsomeAplantself-pollinations).Likewise,theseedinlotBcon-tainsbothBxAandpureB.Inplantbreeding,youdenotethepedigreeofthecrossbyputtingthema-ternalparentfirstandthepaternalparentsecond,henceAxBdenotesAasthematernalseedparentandBasthepaternalpollenparent.
Inthesecondyear,seedfromthetwolotswillbeplantedintoseparatebeds,preferablyintworeplications(twobedsofeach).Thelotsarekeptseparate,astherecanbeaphenotypicdifferencebetweentherootsofthereciprocalhybridcrosses:AxBandBxA.Whilethereisnoeasygeneticexplanationforthis,inrarecasestherecanbeadiscernabledifferencebetweenthereciprocalhy-brids.Whenharvestingrootsattheendofthefirstseason,evaluatethetwopopulationsforgeneralperformanceandrootshape.Ifitisobviouswhichpopulationissuperiorinperformance,makethis
How to Breed Carrots for Organic Agriculture www.seedalliance.org8
onepopulationthebreedingpopulationanddis-cardtheothers.Otherwise,thehybridrootsfrombothcanbeselectedandcombined.Uponfurtherevaluation,thedifferencebetweenthehybridroots(AxBandBxA)andthepureroots(AxAandBxB)willbecomeobvious.Therootsthathaveresultedfromcross-pollinationareoftendifferentinseveralways,especiallyifthephenotypicdiffer-enceofthetwoparentsispronounced.Ingeneral,thehybridrootswilloftendemonstrateamarkedincreaseinvigorwithincreasedrootand/ortopsize.Thehybridsmayalsoexhibitamarkeddif-ferenceinshapeorcolor,aswellasanobvioushybridshapethatisintermediatebetweenthetwoparents.Incontrasttohybridrootsresultingfromcrossesbetweenthetwoparents,purerootsresult-ingfromself-orsiblingpollinationswillbepheno-typicallysimilartotheoriginalparentalmaterial.Theobvioushybridrootsshouldbeselectedandsavedforthenextphaseofthebreedingprogram.
Mass selectionOnceyouhavecreatedabreedingpopulationthroughcontrolledpollinationortheuseofastraincross,thenextstepistobeginselection.Mass selectionincarrotscanbedonefollowingthebasicprinciplesoutlinedinOSAsIntroduction to On-Farm Organic Plant Breeding.Selectionbeginsbyproducingthecropunderuniformfieldcondi-tionsandwiththeuseofgriddedselectiontoselectevenlyacrossthebreedingpopulation.Fortunately,inbiennialrootcrops,itispossibletogrowtherootstofullvegetablematurityandthenselectthedesiredphenotypebeforereplantingfortherepro-ductivephaseofthelifecycle.Onlythedesired,se-lectedplantswillcross-pollinatetocontributetheirgenestothenextbreedingcycle.Youcanalsoselectplantsastheyre-growfoliageandformflowersintheirsecondseason.Abnormalitiesintheforma-tionanddevelopmentofumbelsandflowerstruc-turesaremorecommonthanmanycarrotgrowersrealize.Theseabnormalitiesshouldbeeliminatedwhenobvious,preferablybeforetheonsetofpol-lination.Selectingbeforepollinationincreasestheefficiencyofmassselection.Selectingforhealthy,reproductivefeaturesandbountifulseedproduc-tionisanimportantandoftenforgottenpartofthebreedingprocess.Whenpracticingmassselectionincarrots,maintainaslargeofapopulationaspos-sible,savingseedfromatleast100to120healthy
plantsineachbreedingcycle.
Family selectionFamily selectioncanbeusedtomakerapidgainsinbreedingcross-pollinatedspecies,andcarrotsarenoexception.RefertoOSAsIntroduction to On-Farm Organic Plant Breedingforthebasicconceptsoffamilyselectionincross-pollinatedcrops.Thebreedingmethoddescribedhereforcarrotsishalf-sibling(half-sib)familyselection.Anothermethodistousepollinationbagstomakeaseriesofself-pollinationsonindividualplantswithflies,whichwouldmakeself-pollinated,orS1,families.
Ahalf-sibfamilyisproducedbysavingseedfromasinglecarrotplantthathasbeenopenlypollinatedbyotherplantsofaselectedpopulation.Theseedfromthissingleplantallsharethesamemother,whilethepaternalinheritancemaycomeviapollenfromanyoftheotherplantsinthepopulation.Bysystematicallyselectinghalf-sibfamiliesforseveralgenerations,youcanretainfavorabletraitswhileavoidingsevereinbreeding.
Breeding timelineThefollowingtimelineisbasedonOSAsapproachtobreedingcross-pollinatedcropsusingpopula-tionimprovementviatwoapproaches:family selectionandmass selection.Thefamilyselectionmethodisanalternativetothepedigreebreedingusedinmostmoderncarrotbreedingprograms.Sincecarrotsareabiennialcrop,eachbreedingcycleinthistimelinetakestwogrowingseasonstocomplete.Abreedingcycleisasinglegenerationinthereproductivelifecycle.
Year 1Root year Cycle 1:Determineyourbreedingobjec-tivesandevaluatepotentialparentsorbreedingpopulations.Yourpreliminaryinvestigationintowhichcarrotvarietiesarebestsuitedaspotentialparentstomeetyourbreedinggoals,aswellaswhichvarietiesareadaptedtoyourenvironmentandproductionneeds,istimewell-spent,especiallywhenconductingameaningfultrial.Thisprelimi-narystepisveryimportant,especiallyifyoucanidentifyanexistingpopulationwithdesiredchar-acteristicstoselectfromortwoparentsthatarephenotypicallysimilarbuthavedifferentdesirabletraits.Eitherofthesecaseswillusuallysavetime
How to Breed Carrots for Organic Agriculture www.seedalliance.org9
whenperformingon-farmbreedingwithabien-nialcrop.Ifgoodparentalmaterialisidentifiedinatrial,itcanbeusedasasourceforrootsofthese-lectedparentsandallowedtoflowerandintermateinthesecondyear.Inordertopotentiallyusetrialrootsattheoutsetofabreedingproject,producealargeenoughpopulationofeachaccessioninthetrialtoselectandharvestatleast60to80rootsfromtouseasparents.Whileonly20to30rootsareneededtoperformastraincrossinthesecondyear,itisimportanttostoreatleasttwiceasmanyrootsasyoupredictwillbeneeded,sinceaper-centageofstoredrootswillrotorbeginsproutingexcessivesecondaryroots.Selectedrootsshouldbehealthyandundamagedwithminimaltolittlesproutingwhenexaminedthefollowingspring.Rootsthathaventsprouted,andthatappearingoodcondition(freeofdamage,injury,ordisease),canbegoodbreedingstockwhendevelopingcarrotvarietiestomarketafterlong-termstorage.
Year 2Flower year Cycle 1:Inthissecondseasonofthefirstbreedingcycle,youwillplantatleast20to30parentalrootsofeachvarietyafterafinalselectionfortheirstorability.FollowthestepsformakingastraincrossdescribedintheMaking the cross-pollinationsection.Atseedmaturity,harvestseedfromthetworowsseparatelyintotwoseparatebagsmarkedappropriately:AxBorBxA.
Year 3Root year Cycle 2: Seedharvestedfromthetwoseparateparentalrowsinyear2shouldbesownintoseparaterowsandgrowntovegetablematu-rityforevaluation.Evaluateboththefoliarcharac-teristicsandtherootsofbothrowsatfullmaturity.Ifthereciprocalhybridsaresimilarinallcharac-teristics,combinethemintoasinglepopulation.Iftherearediscernabledifferencesbetweenthetwopopulations,choosethesuperiorpopulationforselectionanddiscardtheother.Eachoftheserowswillproducetwobasictypesofroots:thosethatareobvioushybridsbetweenthetwoparents,andthosethatarerecognizableastheparentaltype(seeStrain crosssectionabove).Selectasmanyhealthyhybridroots(atleast100ifpossible)forstorageandreplantinginyear4.
Year 4Flower year Cycle 2:Afterstorage,selectatleast40to60ofthehealthiestrootsinspring.Planttheserootsassoonasspringconditionsstabilizeandthereisnothreatofhardfrosts.Planttheserootsinanopen,isolatedfieldatleastonemilefromotherfloweringcarrotsorQueenAnnesLace.Alternatively,planttheserootsinameshisolationtentwithintroducedpollinatinginsects.Theplantsarethenallowedtofreelyintermate(openlypol-linate).Plantsshouldbeevaluatedregularlyastheycometofullflowerforanyabnormalitiesintheirgrowthorreproductivetraits.Carrotplantswillof-tenproduceasmallpercentageoffloweringplantswithobviousdeleterioustraits,suchasleavesoriginatinginumbelsorumbelsborneonjointedflowerstalks,andtheseneedtobeeliminated.
Mass selection:Atthispoint,ifyouprefertoonlypracticemassselection,harvestseedattheendoftheseasonfromallhealthyplantswithoutobviousflawsasabalancedbulk.Thismeansthatarough-lyequalquantityofseedisharvestedfromeachplantinthepopulationandiscleanedandmixedtogetherintoonebulkedpopulation.
Family selection:Attheendoftheseason,harvestseedfromallremaininghealthyplantswithoutobviousflaws,andthencleanandbagseparately.Eachoftheresultingseedpacketswillcontainseed
Strain cross hybrid progeny: Pictured here are six hybrid roots from a strain cross, flanked by the two parents of the cross. The six hybrid roots in the middle exhibit a phenotype that is intermediate between the parents. The hybrid roots also demonstrated notable vigor in their foliar growth in the field. Interestingly, the hybrid roots are obviously later in their root maturity as a vegetable crop.
How to Breed Carrots for Organic Agriculture www.seedalliance.org0
thatarelargelytheresultofsiblingmatingandeachisconsideredahalf-sibling(half-sib)fam-ily.Therewillalsobeapercentageofseedineachhalf-sibfamilypacketthatistheresultofself-polli-nationofthatplant.Theseseedpacketsarenum-beredsequentially.
Year 5Root year Cycle 3: seespecificsformassselectionandfamilyselectionasfollows.
Mass selection:Plantseedofthebulkedpopula-tionintouniformfieldconditions,payingattentiontosoiltype,fertility,andirrigation.Plantalargeenoughplottoproduceatleast1,000to1,200car-rots.Inmassselectionofarootcroplikecarrots,alargepopulationofatleast1,000rootsprovidesforgoodselectionopportunities.Growthecroptothestageofvegetablematuritythatfitsthemarketyouareaddressinginyourbreeding.HarvestandselectthecropforbothrootandfoliarcharacteristicsusingthegriddedselectiontechniquedescribedinOSAs Introduction to On-Farm Organic Plant Breed-ing.Storeatleast200to300well-selectedroots.
Family selection:Planttheseedofthese40to60familiesintoshortrows(6to9ft/2to3m)inthefashionofareplicatedtrial,withatleasttworan-domizedreplicationspreferred.Theseprogenyrowscanbeevaluatedforalloftheimportantfoliartraits,fromseedlingvigor,canopydevelopment,andfoliardiseaseresistancethroughoutthesea-son.Atrootharvest,evaluateallroottraits.Themostpromisingfamilieswillexhibitsuperiortraitsinamajorityoftheroots(atleast60to65%)foranumberofthebreedinggoals.Thisisoftenonlyafractionofthehalf-sibfamiliesthatareoriginallyproducedinthepreviousyear.Inourexperience,thiswillbeabout20to25%ofthefamilies,or4to5familiesforevery20familiesproduced.Thebestrootsfromthesesuperiorfamiliesarethenselectedaftereliminatingatleast25to35%oftheless-than-idealroots.Selectedrootsfromthesuperiorfamiliesarethenstoredinindividualfamilybagsforcontinuedselectionandbreedinginyear6.
Year 6 Flower year Cycle 3: seespecificsformassselec-tionandfamilyselectionasfollows.
Mass selection:Evaluatetherootsfortheirstorabil-ityandselectthebest150to200rootsforreplant-inginisolation.Selectrootsthathavesomecom-binationofthetraitsofinterest,butknowthatyouwillprobablynotfindalargepercentageofrootsthathaveallornearlyallofthetraitsyouaretryingtoisolateinyourdesiredideotype.Plantsshouldalsobeevaluatedforanyfoliarorfloweringabnor-malities.Eliminatetheseplantsbeforepollinationoccurs.Harvestseedatseedmaturityasabalancedbulkasyoudidinyear4.
Family selection:Thestoredrootsfromthesupe-riorselectedfamiliesinyear5areplantedinanopenfieldinindividualfamilyrows.Asbefore,dur-ingflowering,eliminateanyindividualsfromthesefamiliesthatexhibitaberrantreproductivegrowth.Ifafamilyhasalargepercentageofplantswithaberrantfoliarorreproductivegrowth,eliminatetheentirefamilyrow.Allowallhealthyfamiliestoopenlypollinateusingnativeorintroducedpollina-tors.Attheendoftheseason,harvest,cleanseedfromeachofthesefamiliesseparately.
Year 7Root year Cycle 4:Atthispointyouwillessentiallyrepeattheprocedurefollowedinyears5and6forbothmassselectionandfamilyselection.
Mass selection: Plantthebulkedpopulationagainasyoudidinyear5withatleast1,000rootsforselection.Thecropproducedthisyearshouldhaveahigherpercentageofrootsthatexhibitcharacter-isticsyouaretryingtocombinethroughselection.Selectandstoreatleast200oftheserootsasyoudidinyear5.
Family selection:Repeattheprocedureofyear5byevaluatingtheselectedsuperiorfamiliesfromthepreviouscyclebasedonfoliarandrootcharacteris-tics.Apredictableoutcomeatthispointinhalf-sibfamilyselectionistofindonly1or2familiesfromtheapproximately4or5selectedfamiliesthatareworthyofcontinuedbreeding.Thisisespeciallytrueifthephenotypesoftheparentsaresimilarasdiscussedbelow.Asthefamiliesarenarroweratthispoint,youcanincreasetheselectionpressureyouapplytotherootsoftheselectedfamilies.Iffamilyselectionrevealsthatonefamilyisclearlysuperior,selectingfromthispointforwardwill
How to Breed Carrots for Organic Agriculture www.seedalliance.org
bethesameasisusedinmassselection.Ifselect-ingdowntoonefamily,retainatleast100to150rootsbeforeproceeding.Iftwoormorefamiliesareworthyofselection,proceedasinyear5bystoringrootsoftheselectedfamiliesseparately.Fortwoormorefamilies,storeatleast80to100rootsforfloweringinthenextyear.
Year 8 Flower year Cycle 4:Repeattheprocedureforseedproductionoftheselectedrootsasinyear6forbothmassselectionandfamilyselection.Ifyouhaveselecteddowntoasinglehalf-sibfamilyusingfamilyselectioninthiscycle,harvestseedasabal-ancedbulkandproceedtothenextcycle.Practicemassselectionwiththisfamily.
Year 9 and 10 (and beyond)Ifpracticingmassselection,continueasintheprevioustwo-yearcyclesuntilyouhaveachievedadegreeofuniformityinthepopulationthatmeetsyourneeds.Infamilyselectionyouwillhaveeas-ilynarrowedyourchoicetoasinglehalf-sibfam-ilybynow,ifnotbefore.Witheithermethod,youmaynowhaveausefulOPpopulationthatservesasauniquecarrotvariety.Besuretomaintainthepopulationbygrowingatleast100to200rootseachcycleandselectingatleast100to150rootsforseedproductionforsubsequentgenerations.Vigilantselectionpressureisneededtomaintainahigh-qualityOPvariety.
Breeding summaryThenumberofbreedingcyclesdependson1)howsimilarthetwoparentsare,and2)thedegreeofuniformityyouneedforyourproductionand/ormarketdemands.Inthefirstinstance,themoresimilartheparentalphenotypes,thefasteryoumaybeabletoattainuniformityinrelativelyfewbreed-ingcycles.Conversely,themoredissimilartheparentalphenotypesare,themorebreedingcyclesyoumayneedtoattainadistinct,uniformpheno-type.Thesetwo-yearcyclesmustberepeateduntilthedesiredphenotypeisattained.
Plantbreedersofopen-pollinatedvarietiesareal-waysfacedwiththechallengeofhowuniformava-rietymustbetomeetthestandardsofthemarket.TheplantbreederandeducatorR.W.Allardstatesthat,truenesstotypeinanopen-pollinatedpopu-
lationisastatisticalfeatureofthepopulationasawhole;itisnotacharacteristicofindividualplants(Allard,1999).Inotherwords,breedersmustmakeavaluejudgmentonthenumberofcyclesneededtoattainthedegreeofuniformityrequiredfortheirmarketorproductionsystem.Atthepointwherethepopulationproducedthroughthisprocesshassufficientuniformityforthemostimportantpro-ductionandmarkettraits,withsomedegreeofin-herentvariationforinsignificanttraits,thevarietymaybeacceptableforrelease.Thebetteryouknowyourpotentialmarket,thebetteryourchancesofknowingwhenthebreedingpopulationisaccept-ableinthemarketplace.
Seedling vigorcanberatedasthesizeoftheseed-lings,eitherbyratingtheheightaloneorbyratingboththeheightandwidthtogetheratasetnumberofdaysaftertheplantingdate.Werateseedlingvigorat15and30daysinordertoevaluateinthefirsthalfoftheseason.Theseratingsreflectthedaystogerminationandthespecificsoftheplant-ingdepthandotherenvironmentalchallenges.
Canopy development canbemeasuredbytrackingtherateofgrowthofbothheightandwidthofthecanopyanditsrelationshipwithweedcompeti-tiveness.Therateofdevelopment,andsizeoftheoverallcarrotleafcanopyfromearlyintheseasonuntilfinalharvest,mayhaveamarkedeffectonthecropsabilitytocompetewithweedsinor-ganicsystems.
Thematurityismeasuredinthenumberofdaysfromplantinguntiltheroothasfilledoutitsfullshape,includingfillingoutthetipoftheroot(tipfill)andachievingitsfullmarketablesizeandweight.
Top attachmentisasubjectivemeasurementbasedonhowwellthepetiolesareattachedtothecrownoftheroot.Thisisanimportanttraitwhenevaluat-ingprospectivefreshmarketbunchingtypes,andisimportantforanumberofdifferentmechani-calharvestersusedforcarrots.Thetraitisoftengaugedundertherealworldchallengesofbunch-ingorharvestingthecrop.
Disease resistance,includingAlternarialeafblight,Alternariacrownrot,AsterYellows,Bacterialblight,Cavityspot(Pythiumsp.),Cercosperaleaf
How to Breed Carrots for Organic Agriculture www.seedalliance.org2
blight,andRoot-knotnematodes(Meloidogynespp.).Thesearepathogenspeciesforwhichselec-tionforresistanceunderfieldconditionshasbeendemonstratedtobeeffective.
Color(orange,yellow,purple,andredtypes)isbasedoninheritedmajorgenesthatcontrolpig-menttypesincarrots.Thewhiterootcolor,whichisduetotheabsenceofpigment,issimplyinher-itedanddominanttothepigmentedtypes,henceeasilyeliminatedinthegenerationafteranerrantcrosswithQueenAnnesLaceoccurs.Allofthepig-mentedtypeshaveothergeneticfactorsthatcangreatlyenhancetheintensityofthecolor.Enhanc-ingcolorisachievedthroughrepeatedselectionandinter-matingofhighcolormaterialasintensityofcolorisaquantitative trait.
Core coloristhecolorofthexylemtissueoftheroot.Oldercarrotvarietiesoftenhavecoresthathaveadifferentcolorthanthepredominantphloemcoloroftheroot.Thexylemcanalsoexhibitlesspigmentationthanthephloemwhentheyareofthesamerootcolor.Palerxylem(core)colorcansometimesbepredictedwiththeobser-vationofpale-coloredstorageroottips(tails),butanaccurateassessmentofxylemcolorcanonlybedonewellbycuttingthetipoftherootofftoviewinteriorcolor.Thispracticedoesnotinterferewithseedproduction,sincealltheplantreproduc-tiveorgansarederivedfromgrowingpointsinthecrownofthecarrot.
Root shaperequiresselectingforthegeneraltaperoftheroot,whichisbasedonthediameterattheshoulderrelativetothediameteratthetiporbot-tomoftheroot.Selectingforastrongbluntingorfillingoftheroottiphelpstoenforceashifttoalesspronouncedroottaper.
Root tip fill isoftenusedasanindicationthatacarrothasreachedamarketablesize.Selectingforearlybluntingiscommoninalmostallmoderncarrotvarietiestogivegrowersmoreflexibilitywithharvestdates.
Root smoothnessismostassociatedwiththeprominenceanddepthofthelateralsecondaryrootscars,whicharepresentalongtheentirelengthoncarrots.Whentheserootscarsareprominent,it
makestherootappeartoberibbedandroughasopposedtosmoothandsleek.
Flavorincarrotsisquitecomplex,withalargenumberofvolatileflavorcompounds,mostlyterpenoids,givingcarrotstheircharacteristicflavor.Whenterpenoidsareinafavorablebal-ance,therootshaveapleasantcarrotyflavor.Ifterpenoidsaretooprominent,thecarrotcantasteharsh,sometimesdescribedassoapy,piney,oroverlyfloral.Flavorisratedasasubjectivetraitwithtrainedtastersandshouldbeconsideredseparatelyfromsweetness.Therecanbelargedif-ferencesbetweentastersintheirabilitytoper-ceivetheharshflavorsincarrots.
Sweetnessisaprominentpartofcarrotflavorandisusuallyevaluatedbybreedersasaseparatecompo-nentofoverallflavorduringtasteevaluations.
Succulence or textureisanimportantcomponentofcarroteatingquality.Consumersprefercarrotsthataresucculent,tender,andjuicyratherthanoverlyhard,tough,orsoft.Onenegativeproductionattributethatcanaccompanysucculentcarrotsisagreatertendencyforrootstobreakorcrack.Whilebreedingcarrotsformoresweetnessorlessharsh-nesshasnotbeenfoundtohaveanyaccompanyingnegativeproductionattributes,breedingformore
Blunting of carrot roots: These Rumba carrot roots exhibit different degrees of blunting or root tip fill, which is the rounding of the root tips that occurs in some variet-ies as the crop matures. Note that the third root from the right has the most well filled tip of these roots.
How to Breed Carrots for Organic Agriculture www.seedalliance.org3
succulencecanintroduceproductionchallenges.Storability of rootsisdonebybringingcarrotsoutofstorageatregularintervalsduringtheoff-seasontoevaluatetherootsfortheirfirmnessandabilitytoresistrotandnotsproutlateralrootsorshoots.Rootscanalsobeevaluatedforflavorandsweet-nessatthesesameintervals.
GlossaryAnther:male,pollen-bearingstructuresoftheflower.
Biennial:thetypeofplantthatnormallyproducesonlyvegetativegrowththefirstgrowingseason,overwinters,andthenproducesaseedcropafterwhichtheplantdies.Theplantrequirestwogrow-ingseasonstocompleteitslifecycle.
Cytoplasm: thecontentsofacellbetweenthenucleusandthecellwall.Inreproduction,thecytoplasmicconstituentsfromthefemalepar-entbecomepartofthecytoplasmoftheoffspring.Theremaybeatransferoftraitsdeterminedbyorganellescontainedinthecytoplasmnotassoci-atedwithchromosomeswithinthenucleus.
Cytoplasmic male sterility (CMS): Sterilityofthemalereproductiveorgansthatisunderextra-nucleargeneticcontrol,usuallygeneticmaterialinmitochondriaorchloroplastorganelles.Thissteril-ityisinheritedmaternally.Itoccursnaturallyinmanyspeciesandhasbeenidentifiedinwellover100cropspecies,includingcarrots.
Family:agroupofgeneticallyrelatedplants.Oftenthenatureoftherelationshipisspecified.Asexamples,seehalf-sib families, full-sib families,andS1 families.
Family selection:selectingindividualplantsorfam-iliesbasedontheoverallperformanceofafamily.
Feral:adomesticatedspeciesthathasrevertedtoawildoruntamedstate.
Full-sib family:afamilystructurewhereplantsinafamilysharethesamemotherandthesamefather.
Genotype:thegeneticcompositionoftheplant.
Germplasm: theentirecollectionofgeneticmate-rialforanygivencropspecies.
Half-sib family:afamilystructurewheretheplantsinafamilysharethesamemother.
Hybrid:theproductofacrossbetweengeneticallydistinctparents.
How to Breed Carrots for Organic Agriculture www.seedalliance.org
Hybrid vigor:theincreaseinvigorofhybridsovertheirparentaltypes,alsoknownasheterosis.
Ideotype:torthepurposesofthistext,animag-inedcropvarietyrepresentingtheidealtobereachedthroughabreedingproject.
Inbred:avarietyproducedbysuccessiveinbreed-ingoveranumberofgenerations.Alsocalledaninbredline.
Inbreeding depression:thedecreaseinavarietysfitnessduetoinbreeding.
Inflorescence:thearrangementofplantflowers,suchasumbel,raceme,spike,tassel,andpanicle.
Male sterility:aninheritedfactorusefulinhybridseedproduction.Itpreventsviablepollenfrombeingproduced.
Mass selection:aformofselectionwhereindi-vidualplantsareselectedbasedontheirindi-vidualperformance.
Nuclear restorer genes:thesearenucleargenesthatcanrestorefertilityinplantswithcytoplas-micmalesterility(CMS).ThesegenesareusuallydominantintheirexpressionandwhenpresentwillrestoremalefertilitytoplantswithCMS.ThesegenesareoftenabundantinwildpopulationsofplantswithnaturallyoccurringCMS.
Open-pollinated:seedproducedasaresultofnaturalpollinationasopposedtohybridseedpro-ducedasaresultofacontrolledpollination.AlsocalledanOP.
Phenotype: theobservable,outwardappearanceofacrop.
Phloem:thevasculartissueinplantsthattrans-portssugarsandothermetabolitesfromthephoto-synthetictissuetotherestoftheplant.Incarrots,thephloemconstitutesthetissuesurroundingthecentralcoreoftheedibleroot.
Polygenic trait:relatingtoorcontrolledbymul-tiplegenes.
Protandry: thereproductivestateofaflower-ingplantwherethemalereproductiveorgansorantherscometomaturitybeforethefemaleflow-eringparts.
Reciprocal cross:twomirroredcrossesmadebetweenasinglesetofparentswhereeachparentservesasboththefemaleandthemale.
Quantitative trait:synonymouswithpolygenictrait(seepolygenic).
S1 family:afamilystructurewheretheplantsinthefamilyallresultedfromthesameself-pollination.
Stigma:theupperpartofthepistilthatreceivesthepollen.
Strain:atermusedbybreedersthatisessentiallytheequivalentofavariety,althoughstrainisalsousedtodescribeaspecificvariantofavarietythatisslightlydifferentfromtheoriginalvarietyinitsphenotypeoradaptation.
Strain cross:atermusedbybreederstospecifyacrossbetweentwodifferentvarietiesorstrainsofacropwheremultipleindividualsofbothstrainsareusedtocreatethebreedingpopulation.
Variety:agroupofplantsofaparticularspeciesthatsharesasetofcharacteristicsortraitsthatdif-ferentiatesitfromothervarietiesofthesamecrop.Thesecharacteristicsmustbedistinctandrela-tivelyuniformacrossalloftheplantsofthevariety.Varietyisasynonymforcultivar.
Vernalization:theexposuretocertainconditionsofcoldtemperatureandphotoperiodtoseedandyoungplants,whichpromotesfloralinductionwithoutdevelopmentoftheplant.
Xylem:thevasculartissueinplantsthattransportswateranddissolvednutrientsfromtheroottoallpartsoftheplant.Incarrots,thexylemconstitutesthecentralcoreoftheedibleroot.
How to Breed Carrots for Organic Agriculture www.seedalliance.org
References and ResourcesAllard,R.W.1999.Breedinghybridvarietiesofoutcrossingplants,pgs.198-199.Principles of Plant Breeding,2ndEd.JohnWileyandSons.NewYork.
Colley,M.R.andJ.R.Myers.2007.On-farm Variety Trials: A Guide for Organic Vegetable, Herb, and Flower Producers.OrganicSeedAlliance,PortTownsend,WA.
Navazio,J.P.,M.R.Colley,andJ.Reiten.2010.Princi-ples and Practices of Organic Carrot Seed Production in the Pacific Northwest.OrganicSeedAlliance,PortTownsend,WA.
Zystro,J.andJ.P.Navazio.2014.Introduction to On-farm Organic Plant Breeding.OrganicSeedAlliance.PortTownsend,WA.
How to Breed Carrots for Organic Agriculture www.seedalliance.org6
AuthorsCompleted 20John Navazio, Organic Seed AlliancePictures courtesy of John Navazio (OSA) and Laurie McKenzie (OSA) unless otherwise noted
Producer-Professional ReviewedAs an institutional standard, all OSA publications are reviewed by both scientific researchers and profes-sional producers.
Educational Materials
This publication is protected under Creative Commons licenses: Attribution, Non-Commercial & Share Alike.
We believe in protecting intellectual property (IP) in a manner that promotes creativity and innovation in the interest of the public good. We encourage you to learn more about the Creative Commons, the Open Source movement, and other alternative IP models. Regarding this material, Organic Seed Alliance is the original author and license holder. You are free to copy, distribute, display, and perform the work, and to make derivative works under the following conditions:
Attribution. You must give the original author credit.
Noncommercial. You may not use this work for commercial purposes.
Share Alike. If you alter, transform, or build upon this work, you may distribute the resulting
work only under a license identical to this one.
For any reuse or distribution, you must make clear to others the license terms of this work.Any of these conditions can be waived if you get permission from the copyright holder.
Your fair use and other rights are in no way affected by the above.
For PDF versions of this and other seed publications, please visit us at www.seedalliance.org Organic Seed Alliance 20