Download 5. Why does the organic sector not want `PPF hybrid varieties`?

5. Whydoestheorganicsectornotwant‘PPFhybridvarieties’?
Noinbredplantswantedinhybridseed
Section3explainsthattheadvantageofhybridvarietiesistheiruniformity.However,beforeplantsofa
hybridvarietyareactually100%uniform,thereisanotherproblemtobetackled.Themotherlineshould
notbeallowedtoself-pollinate,asotherwisetheseedlotwillcontaindeviatinginbredplants.Thereare
variouswaysofpreventingthis,dependingonthecrop.
Manualemasculationandmanualpollination
Manualremovalofstamens(‘emasculation’)andpollinationisrelativelyexpensive.Inthecaseofcrops
suchastomatoes,peppers,cucumbers,courgettesandpumpkinsthisisworthitandiscarriedout(see
Figures1and2).Oftenthestamensarefirstofallremovedfromthemotherlinetoensurethatselfpollinationcannottakeplace.
Figure1.Manualremovalofstamensfromatomatoflower(Photo:J.Myers,OSU)
Figure2.Manualpollinationoftomatoflowers(Photo:F.Meijer-Dekens,WUR)
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Usingnaturalmalesterility
Inthecaseofmostfieldcropsmanualpollinationisnoteconomicallyfeasible.Itmakestheseedtoo
expensive.Theonlyalternativeistolookforgeneticmechanismsasaresultofwhichthemotherline
doesnotself-pollinate.Inthecaseofcropssuchascarrots,onionsandleeksmalesterility(MS)
sometimesoccursnaturally.Thesemale-sterileplantscanberecognisedbythefactthattheirflowersdo
nothavestamens.Theseplantscanbeusedinbreedingasthemotherlineinordertoavoidthemother
linebeingabletoself-pollinate.Thismalesterilityoccursnaturallyinthenucleusofsometypesofcrops
butnotinallcrops.Inthecaseofsomecrops(sunflowersandradishes)malesterilityistobefoundnotin
thenucleusbutnaturallyinthecytoplasmaofthecell;inthiscaseitiscalledcytoplasmicmalesterility,
abbreviatedtoCMS.
Table1.Overviewofseveralcropswithandwithoutnaturalmalesterilityinthenucleus(MS)andcytoplasmic
malesterility(CMS)andpossiblealternatives.
Crops
Cucumber
NaturalMS
No
NaturalCMS
No
Cabbage
No
No
Carrots
Radishes
Tomatoesand
peppers
Onions
Chicory
Yes
Unknown
Notnecessary
No
Yes
No
Yes
No
No
No
Sunflowers
Probablynot
Yes
Alternatives
Cucumbersproduceseparatefemaleandmaleflowersontheplant.
ThereareF1hybridsonthemarketthatproduceonlyfemaleflowers.
Tobeabletoobtainpollenforseedcultivationthefatherlinedoes
havetoproducemaleflowers(usingplanthormones).
‘Self-incompatibility’,i.e.theplantdoesnotacceptitsownpollenbut
prefersthatofanotherplant.Thischaracteristicisoftennot100%
effectiveandsometimesundercertainconditionsproducesupto
around10%inbredplants.However,thisdoesinpracticeworkfairly
well.
Notnecessary.
Notnecessary.
Manualemasculationcanbedonewell(i.e.removingthestamenswith
tweezers).
Notnecessary.
Chicoryalsohasaformof‘self-incompatibility’.Inthe‘normal’hybrid
processinthecaseofchicoryalimitednumberofgenerationsare
inbredandseveralinbredplantswillalwaysbeproduced.
Notnecessary.
Naturalself-incompatibility
Inthecaseofseveralcrops(cabbageandchicory)malesterilitydoesnotoccuratall.Inthecaseofthese
cropsthereisanothermechanismavailable:so-calledself-incompatibility.Thismechanismensuresthata
plant(inmostcases)doesnotacceptitsownpollen.Itisacomplexcharacteristicandnotallbreeding
companieshaveagoodsetofgenesthatensureself-incompatibility.
ArtificialCMSincabbageandchicoryviaprotoplastfusion:PPFhybrids
Breederswantcompletemalesterilityandtrytointroducethischaracteristicfromanother(non-crossable
buttosomeextentrelated)typeofplantartificially.CMSwasintroducedtocabbagefromradishesvia
protoplastfusion(i.e.unnaturally);inthecaseofchicorythiswasdoneusingsunflowers.Inthecaseof
boththesecropscompletesterilityisachievedonlyusingforcedprotoplastfusion,seeFigure6.Tothis
endfirstofallthecellwallisdissolvedusinganenzymetreatment,sothattheprotoplasts(thecells
withoutacellwall)canbefusedusingelectricalstimuliandtheorganellesandthemitochondriaare
combined,asaresultofwhichCMSistransferredtotheotherdesiredspecies.
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Figure6.Processofprotoplastfusion
betweentwodifferentplants.Source:
FiBldossier2001
Protoplastfusion(PPF)isnotadesirabletechniquefortheorganicsector
ThereasonthatPPFtechniquesareformallypermittedwithinorganicfarmingiscomplicated.Itistodo
withinternationaldefinitions,legislationandreferences.Forseveralcountriesthisacceptanceisareason
todrawupadditional‘private’rulesfortheuseof‘PPFhybrid’varietiesthatwereobtainedusingthese
techniques.Severalmarketplayers,suchasDemeter,BiolandandNaturland,haveforbiddentheusein
Germanyofvarietiesproducedusingprotoplastfusion.
In2013therewasanuproarintheGermanmediaabout'geneticallymodifiedorganicchicory'.Thiswas
aboutorganicchicorythathadbeencultivatedusingseedfromaso-calledPPFvariety(conventionally
producedseed).
HowcangrowersknowthattheyarenotgettingaPPFhybridofcabbageandchicory?
Noteveryseedcompanyindicateswhichhybridvarietiesweredevelopedonthebasisofprotoplast
fusion.Seedcompaniesintheorganicsectorconsciouslytakeintoaccounttheobjectionstoprotoplast
fusionandputonlyorganicseedofF1hybridvarietiesonthemarketdevelopedonthebasisofselfincompatibility(so-calledSIvarieties).ThisdoesnotalterthefactthatthereareonlyafewsuitableSI
chicoryvarietiesonthemarketandtherearenoseedcompaniesthatinvestinthedevelopmentofnewSI
chicoryvarieties.InthecaseofcabbagethereareSIvarietiesbeingmaintained,inparticularbyBejo,
Enza/VitalisandRijkZwaan.Butitisclearthatthereneedstobeinvestmentinthebreedingofnew
organicvarieties.
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