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4.Whatisthedifferencebetweenopen-pollinatedvarietiesandhybrid varieties? Thequestionthatisoftenaskedintheorganicsectoris:‘Whatisthedifferencebetweenahybridanda open-pollinatedvariety,andwhataretheadvantagesanddisadvantages?Andwhatfitsinbestwith organicfarming? Whatisa‘open-pollinated’variety? Aopen-pollinatedvarietyisproducedusingthetraditionalmethodofcrossingandthenselectionof offspringinseveralgenerations(basepopulation),seeFigure1. Afterafewyears(usuallyafter5-6generations)ofsystematicselectionthevarietybecomesstableand thecharacteristicshardlyeversegregateoutagain.Thismeansthatalltheoffspringarevirtuallythe same,whichiswhytheterm'open-pollinated'isused.Soplantscomefromseedsofopen-pollinated varietieswithvirtuallythesamecharacteristicsasthevarietypurchased. Figure1.Diagramofthebreedingofanopen-pollinatedvariety(left)andanF1hybrid variety(right)(courtesytoM.Haring) F1hybrid Open-pollinated variety Crossing X Basepopulation Offspringinthe Inbredparent Inbred sub-sequent parent lineA generationsline line Selectionfrom F1hybridseed thepopulation OffspringofanF1hybrid Newselection (=F2seed) Whatisa(F1)hybridvariety? F1hybridmeansliterally‘firstoffspringafteracrossing’.InthecaseofF1hybridsthebreedingprocessis dividedintotwophases:inbreedingandcombinationsofcrossings.Sotheprocessismorecomplicated andrequiresmoreinterventionbybreedersthaninthecaseofanopen-pollinatedvariety. Thefirststepistodevelopparentlines.Theseparentslines(themotherandthefather)shouldeachbeas uniformaspossible;andtheparentlinesforacrossingshouldalsobeverydifferent.Uniformparentlines areproducedbyinbreeding.Inthecaseofself-pollinators(tomatoes,peppers)thisisfairlysimple:selfpollinatorsarenaturalinbreeders.Butinthecaseofcross-pollinators(suchaschicoryandcabbage)all 8 sortsoftechniquesareneededtocarryout(manual)inbreeding.Thesecondstepistotestwhich combinationofinbredlineswillproduceagoodF1hybridoncrossing. Onceyouhavevariousinbredparentlines,youcanquicklymakenewcombinations(varieties).Thishas beenoneofthemotivationsforbreederstomovefrom‘open-pollinated’varietiesto‘hybrid’varieties. Afterall,thebreedingofanewvarietycantaketenyears.Sobreedershavealwayslookedforfasterways ofbreeding.Hybridisationhasbeenanimportantstepinthis. Advantagesofopen-pollinatedvarieties Thefirstadvantageofopen-pollinatedvarietiesisthatthereisalwayssomeformofgeneticvariation betweentheplantsinthefieldandsodiseasesspreadlessfastthaninthecaseofgeneticallyidentical plantsofahybridvariety. Anotheradvantageisthatgrowerscanpropagatethesevarietiesthemselves,i.e.theycanrepeatedly obtainseedandsowitagain,seeFigure2.Theseedproductioncyclecanthereforebecontinued indefinitely,fromgenerationtogeneration.Asthereisalwaysalittleundetectedvariationinanopenpollinatedvariety,youhavetoapplysomeselectioninthisseedproductioninordernottoobtaintoo muchnon-desirablevariation.Avarietycanotherwise‘degenerate’anddeviatetoomuchfromthe characteristicsdesiredoriginally. Figure2.Anorganicgrowerinacabbagefieldherselfselectingcabbagesfromanopen-pollinated variety(left)andobtainingseedsfromthem(right) Disadvantageofopen-pollinatedvarieties Thefarmsavedseedofopen-pollinatedvarietiesobtainedbygrowersisadisadvantageforbreeders. Theymissoutonincometofundtheirbreedingofnewvarieties.Iftheorganicsectorwantstoencourage thebreedingofnewopen-pollinatedvarieties,thecostsofbreedingneedtobeinvesteddifferently.Read aboutthisinSection10. AdvantagesofanF1hybridvariety Thefirstadvantageofhybridseedsforgrowersisthehighdegreeofuniformity:alltheplantsare,for example,readyforharvestingatthesametimeandarethereforesuitableforaone-off,mechanical harvest.Theylookalikeandtheyprovideauniformsorting.Asecondadvantageisthatinsomecases thereisadditionalgrowthvigour(‘heterosis’),asaresultofwhichtheplantgrowsmorevigorousor producesahigheryield. 9 DisadvantagesofanF1hybridvariety Thedisadvantageforgrowersisthefactthattheirownfarm-savedseeddoesnotproduceusableseed. HybridvarietiescaninprincipleproduceseedbutintheF2thecharacteristicssegregateoutagainanda variationisproducedthatisnotwantedbythemarket.Inthiswayseedcompaniesprotectthemselves againstfarmsavingseeds.Thismakesgrowersdependentontheseedcompanies,whohavetoconstantly crosstheinbredparentlinestobeabletobringnewF1seedontothemarket.PartlyforthisreasonF1 seedismoreexpensivethanofanopen-pollinatedvariety.Butforsomegrowerstheadvantages compensateforthedisadvantages.Inorganicfarminghybridvarietiesarepermittedandareusedin certaincrops. Whyisinbreedingnecessaryinthecaseofahybridvariety? Inbreedingofparentlinesmeansthatdesiredvarietycharacteristicsare‘fixed’faster,asaresultofwhich theparentlineseachbecomeveryhomogenous.Thentwodistinctiveparentlinesarecrossed,which producestheso-calledF1hybridseed.TheplantsfromF1seedoffspringhavethecharacteristicsofthe twoparentlinescombinedandalltheplantsareidenticalandthusproduceauniformfield.Inthecaseof anopen-pollinatedvarietymoredeviationsarepossible. Arehybridvarietiespermittedinorganicfarming? Aslongastheseedisproducedunderorganic growingconditions,hybridvarietiesarepermittedin organicfarming.Thereareseveralhybridvarieties whoseparentlineshavebeentooweakenedby inbreedingandthatcanproducegoodseedonly withtheuseofpesticides;thesevarietiesare thereforenotdesirableintheorganicsector. Figure3.Breedingforahybridvarietyforcabbage: manuallyinbreedingandcrossing(Photo:J.Myers, OregonStateUniversity) Bio-dynamicfarmingandhybridvarieties Bio-dynamic(BD)farmingisaspecificwayoffarmingwithinorganicagriculturalmovementthathasits ownvisionandhasadditionalrulesinadditiontothoseoforganicfarming.Forbio-dynamicfarmingthe developmentofanopen-pollinatedvarietyisthemostnaturalwayofbreeding.Noartificesareused, suchasinbreedinginthecaseofplanttypesthatarenaturallycross-pollinators.FromaspecificBDpoint ofviewthepropagationofone'sownseedfitsinwiththedevelopmentofone's‘own’farmindividuality. Afterall,byrepeatedlyproducingseedgrowerscanadaptavarietytosuittheirownbusiness.Theydo thisbyconstantlyselectingcertainplanttypesintheoffspringoftheseedthatfitinbestwiththefarm andthelocalconditions.Thefactthatanopen-pollinatedvarietyisconstantlyabletoproduceavital subsequentgenerationisinkeepingwiththeBDvision.Hybridvarietiesthereforefitinlesswellwiththe BDfarmingperspective. 10