ÿWPC' ÀÌUZõµÊ šFé(bókúH—%:•cºšvU˜fDQô13U$()b3å;[å.Ùbtp¼E^¢¶jæÔÁ`<ÄŸJÑCþ¯ÞóËqª? ©“P+ JÀJ€¨pIVUTqƒ÷ÿ§âšÅ$0W´æEI«¿‹žN”„^˜)PJœ»h I©% z[øÓ+°ÝÀ¤éºág%“å“\ÁˆǶIɇé¿|‹Ù¶èW„_Ø}Ó™ãWœ >eù³:-,‹Ã~mr†]]ÑÛÙVý’SÍë…†š€núgn‘þ'˜ü@_¹Ž ;§*â¬Ñãì&2Xø#X®3HˆÿSeª 10,000€spores/g€of€soil)€in€the€greenhouseÏ(Torto€et€al.,€1996)€than€in€the€field€(<3000€spores/g€of€soil;ÏRoy€et€al.,€1997).€High€pathogen€rates€overcome€both€partial€andÏcomplete€plant€resistance€to€disease€ññpathogenesññññpathogensññ€(Parlevliet,€1979;ÏTooley€and€Grau,€1982)€including€the€soybean€„€F.€solaniÏinteraction€(Torto€et€al.,€1996;€Gray€and€Achenbach,€1996;ÏHartman€et€al.,€1997).Ìà  àWe€compared€selection€for€€field€resistance€to€SDS€in€theÏgreenhouse€by€leaf€scorch€severity€at€three€inoculum€rates.€TheÏimplications€for€breeding€and€biotechnology€are€considered.ÌÐ  0€  Ðà@ ìàò òMATERIALS€AND€METHODSó óˆÐ ° Ðà  àThe€genetic€material€included€30€Fòò5:10óó€recombinant€inbredÐ h Ðlines€(RILs)€(a€subset€of€a€population€of€100€lines)€from€theÏcross€of€'Essex'€(Smith€and€Camper,€1973)€x€'Forrest'€(HartwigÏand€Epps,€1973)€and€10€soybean€cultivars€of€diverse€geneticÏbackground.€Essex€is€susceptible€to€SDS€while€Forrest€isÏresistant€to€SDS€(Gibson€et€al.,€1994;€Hnetkovsky€et€al.,€1996).ÏThe€RILs€were€selected€by€disease€index€(Gibson€et€al.,€1994)Ïmean€to€include€three€groupsññ›ññññññ›ññññ€(10€RILs€per€group)€that€contrastedÏfor€SDS€leaf€scorch€score€by€the€mean€of€five€field€environmentsÏover€five€years€(Fòò5:6óó€to€Fòò5:10óó).€€The€groups€were:€(1)€fieldÐ À Ðññœññresistant;ññ›ññ€the€10€most€resistant€of€the€100€ññœññlines,€eight€of€whichÏwere€significantly€more€resistant€than€Forrest;€(2)€fieldÏpartially€resistant;€the€10€of€the€100€lines€around€theÏpopulation€median;ññ›ññ€ññœññand€(3)ññ›ññ€field€SDS„susceptible;€the€10€leastÏresistant€of€the€100€ññœññlines,€all€of€which€were€more€susceptibleÏthan€Essex;€(Hnetkovsky€et€al.,€1996).ññ›ññ€ññœññAlthough€SDS€resistance€inÏthe€field€is€a€partial€resistance€controlled€by€several€genes,Ïð ðresistanceðð€and€ð ðpartial€resistanceðð€will€be€used€to€refer€toÏgroups€1€and€2€respectively€in€this€paper.€€€The€10€diverseÏsoybean€cultivars€included€four€that€were€susceptible€to€SDS€inÏthe€field€and€six€that€were€resistant€to€SDS€in€the€field.Ìà  àThe€òòñ ññ ñF.ñ!ñ€ñ!ññ"ññ"ñsolanióó€isolate€(ST90)€was€isolated€from€SDS€infectedÐ  #ð, Ðroots€of€the€soybean€cultivar€ððSpencerðð€in€Stonington,€IllinoisÏin€1990€by€single€spore€isolation€(Stephens€et€al.,€1993).€TheÏstrain,€stored€on€Bilays€medium€was€subcultured€on€PDA€medium€andÏused€to€infest€a€1:1€(v/v)€mixture€of€cornmeal€and€SiOòò2óó€(SigmaÐ @)$4 ÐChemical€Co.,€St€Louis,€MO).€After€incubation€at€room€temparatureÏfor€10€days€(O'Donnell€and€Gray,€1995)€five€cmòò3óó€of€the€inoculumÐ ,`'8 Ðwas€added€to€250€ml€of€sterile€water€and€the€average€count€ofÏspores€(in€ten€€samples€of€1€ml)€determined€on€a€hemocytometerÏunder€a€microscope.€Spore€counts€were€used€to€calculate€theÏvolume€of€culture€ññ›ñññ"ññ ñ›ñ ññ"ñnecessary€for€each€inoculum€rate.Ìà  àFour€experiments€were€conducted€in€the€greenhouse€at€theÏSIUC€Horticulture€Research€Center€in€Carbondale,€IL.€The€firstÏtwo€experiments€evaluated€the€selected€recombinant€inbred€linesÏfor€leaf€scorch€resistance€by€SDS€disease€severity€(DS)€at€threeÏinoculum€rates€(high=10òò4óó,€moderate=5x10òò3óó,€and€low=3.3x10òò3óó€sporesÐ ð@  Ðper€cmòò3óó€of€soil).€The€third€experiment€evaluated€€recombinantÐ X¨  Ðinbred€lines€at€a€lower€inoculum€rate€of€2x10òòòò3óóóó€spores€per€cmòòòò3óóóó€ofÐ À Ðsoil.€The€fourth€experiment€evaluated€diverse€cultivars€at€4x10òòòò3Ð (x Ðóóóóspores€per€cmòòòò3óóóó€of€soil.€Experiments€were€conducted€betweenÐ à ÐNovember€œ1,€1996€and€March€›1,€1999.€€Plants€were€grown€with€a€14„¼hour€photoperiod€and€the€air€temperature€ranged€from€20òò+óó2€òòoóóC€atÐ `° Ðnight€and€27òò+óó2€òòoóóC€during€the€day.Ð È Ðà  àThe€plant€growth€medium€consisted€of€a€1:1€(v/v)€mixture€ofÏsterile€sand€and€soil€in€all€experiments.€òòF.€solanióó€culture€andÐ ˜è" Ðplant€growth€medium€were€mixed€in€three€ratios€(v/v)€(1:40,€1:80,Ïand€1:120)€for€the€first€two€experiments.€After€a€carefulÏanalysis€of€data€from€the€first€three€experiments,€a€fourthÏexperiment€was€conducted€using€an€inoculum€rate€between€theÏmoderate€and€low€values€(v/v)(1:100€or€4x10òòòò3€óóóóspores€per€cmòòòò3óóóó€ofÐ  #ð, Ðsoil)€on€diverse€soybean€cultivars.Ìà  àAll€experiments€were€planted€in€a€randomized€complete€blockÏdesign.€Each€recombinant€inbred€line€was€evaluated€in€twoÏreplications€per€experiment€while€each€cultivar€was€evaluated€inÏfive€replications.€Non„inoculated€control€plants€were€included€inÏall€experiments.€Two„week„old€seedlings€were€transplanted€onto€òòF.Ð ,`'8 Ðsolanióó€infested€soil€in€four„inch€styrofoam€cups€and€keptÐ ° Ðsaturated€to€two€inches€with€water€for€four€weeks.€SDS€diseaseÏseverity€(DS)€was€rated€at€21€days€after€inoculation€on€a€scaleÏof€1€to€9€(Njiti€et€al.,€1996).€Ìà  àIn€the€third€experiment€root€resistance€was€evaluated€asÏcolony€forming€units€per€gram€of€root€as€follows.€Roots€wereÏwashed,€oven„dried€at€28òòoóóC€for€48€h,€ground€using€a€Wiley€cuttingÐ  p  Ðmill€(Thomas€ScientificòòTmóó,€Swedesboro,€NJ),€weighed,€andÐ ˆØ  Ðsuspended€in€2,000€ml€of€distilled€water.€One€ml€of€theÏsuspension€was€transferred€onto€each€of€five€petri€platesÏcontaining€a€modified€Nash€and€Snyder€(1962)€medium.€The€mediumÏwas€20€g€agar,€15€g€peptone,€1€g€KHòò2óóPOòò4óó,€0.5€g€MgSOòò4óó.7Hòò2óóO€and€1€LÐ (x Ðdistilled€water,€autoclaved€at€110òòòòoóóóóC€for€40€min€and€cooled€toÐ à Ð42òòoóóC€before€0.3€g€streptomycin€sulfate,€0.1€g€neomycin,€0.1€gÐ øH Ðchlortetracycline,€0.05€g€rifampicin,€and€0.23€gÏpentachloronitrobenzene€(PCNB)€(Terrachlor,€Uniroyal€ChemicalÏCo.,€Vaugntuk,€CT)€were€added.€€Petri€plates€were€poured€andÏallowed€to€set.€Plates€were€inoculated€and€incubated€at€roomÏtemperature€for€14€d.€The€number€of€slow„growing€fungal€coloniesÏwith€few€aerial€mycelia€were€counted€as€colony€forming€units.€ÏThe€colony€forming€units€per€gram€of€root€tissue€(CFU)€wasÏcalculated.Ìà  àData€were€subjected€to€analysis€of€variance€(ANOVA)€(SASÏInstitute€Inc.,€Cary,€NC).€The€lines€within€SDS€group€byÏexperiment€interaction€was€tested€to€justify€pooling€data€fromÏthe€first€two€experiments.€Mean€comparisons€were€made€by€LSDÏ(Gomez€and€Gomez,€1984).€Correlations€were€determined€using€theÏCORR€function€of€MSTATC€(Freed€et€al.,€1990).ÌÐ ,`'8 ЇÓ¼´Óà@ÄÄìàò òRESULTS€AND€DISCUSSIONˆÐ ° ÐResistance€to€leaf€scorchó óÐ (x Ðà  àSDS€leaf€symptoms€were€not€observed€on€plants€grown€on€nonÏòòF.€solanióó€infested€plant€growth€medium.€€There€was€a€significantÐ  h Ðeffect€of€inoculum€rate€in€both€experiments€(Table€1).€DS€meansÏwere€2.8€for€the€low€and€4.0€for€the€moderate€inoculum€rates€inÏthe€first€experiment€and€2.1,€4.0,€and€7.2€for€low,€moderate,€andÏhigh€inoculum€rates€respectively€in€the€second€experiment.€HigherÏòòF.€solanióó€inoculum€rates€were€expected€to€cause€more€severe€SDSÐ pÀ  Ðleaf€symptoms€and€greater€root€rotting€(Gray€and€Achenbach,Ï1996).€Means€of€DS€at€the€high€inoculum€rate€in€the€firstÏexperiment€could€not€be€determined€due€to€the€death€of€numerousÏplants.€Soil€compaction€contributed€to€the€death€of€this€set€ofÏplants€(treatments€were€planted€by€different€individuals)€and€wasÏmonitored€closely€in€subsequent€experiments.Ìà  àOnly€at€the€low€inoculum€rate€was€there€a€significantÏdifference€(P€ðð0.05)€among€the€three€SDS€groups€of€genotypes€inÐ 0€  ÐSDS€disease€severity€in€both€experiments€(Table€2).€The€sporeÏrate€in€the€low€inoculum€treatment€(3,500€spores€per€cmòòòò3óóóó€of€soil)Ð  p$ Ðwas€similar€to€that€in€field€hot€spots€(Roy€et€al.,€1997).€In€theÏgreenhouse,€the€appearance€of€SDS€symptoms€occurred€earlierÏ(vegetative€growth€stages)€than€in€the€field€(reproductive€growthÏstages)€due€partly€to€adequate€soil€moisture€and€a€restrictedÏtemperature€range.€Lines€within€groups€of€genotypes€did€not€varyÏsignificantly€in€SDS€disease€severity€in€the€greenhouse(Table€2).ÏSince€group€members€were€selected€by€similarity€of€response€toÏSDS€in€the€field€low€variation€within€group€was€expected€for€anÏeffective€assay.€Ð X,¨'6 Ðà  àThe€significant€difference€between€replications€(Tables€1&2)Ïin€the€second€experiment€and€modest€heritability€(63%)€indicatedÏthat€the€greenhouse€assay€did€not€control€all€environmentalÏfactors€that€can€influence€SDS€occurrence€and€severity.€Air€Ïtemperature€varied€from€bench€to€bench€and€could€have€influenceÏsoil€temperature€which€has€been€a€major€soil€factor€influencingÏSDS€occurrence€and€severity€in€the€field€(Rupe€et€al.,€1993).€TheÏuse€of€growth€chambers€and€water€baths€may€enable€us€to€test€theÏeffect€of€soil€temperature€on€heritability.Ìà  àThere€was€no€significant€interaction€between€genotype€groupÏand€experiment€(Table€2).€Therefore,€the€two€experiments€wereÏpooled€for€mean€comparison.€Within€each€genotype€group,€SDSÏdisease€severity€increased€with€increasing€inoculum€rate€(TableÏ3).€At€the€high€inoculum€rate€all€three€groups€were€highlyÏsusceptible€(Table€3)€as€expected€(Stephens€et€al.,€1993;€TortoÏet€al.,€1996;€Gray€and€Achenbach,€1996).€Therefore,€high€inoculumÏrates€may€be€responsible€for€the€breakdown€of€field€SDS€Ïresistance€in€the€greenhouse€(Torto€et€al.,€1996;€Stephens€etÏal.,€1993;€Gray€and€Achenbach,€1996€Hartman€et€al.,€1997).€Ìà  àAt€the€low€and€moderate€inoculum€rates,€the€DS€mean€of€theÏfield€SDS€susceptible€group€was€significantly€higher€than€thoseÏof€both€the€partially€resistant€and€the€resistant€groups.ÏHowever,€the€field€partially€resistant€and€resistant€groups€wereÏnot€significantly€different€from€each€other€(Table€3).€AlthoughÏin€the€field€the€group€of€genotype€with€partial€resistance€to€SDSÏhad€a€significantly€higher€DX€means€(7.4%)than€the€group€ofÏgenotypes€with€resistance€to€SDS€(1.2%).€Therefore€the€greenhouseÏassay€was€not€as€effective€as€a€replicated€field€study€forÐ X,¨'6 Ðseparating€cultivars€with€partial€resistance€from€those€withÏresistance.€Ìà  àThe€correlation€between€greenhouse€disease€severity€andÏfield€disease€severity€was€significant€at€the€low€(r€=0.70,€PÏ=0.0001)€and€at€the€moderate€(r€=0.44,€P€=0.02)€inoculum€rates.ÏThere€was€also€a€significant€(P€ðð0.05)€correlation€betweenÐ  X  Ðgreenhouse€disease€severity€and€field€disease€index€at€lowÏinoculum€rate.€The€strong€correlation€between€field€andÏgreenhouse€disease€severities€contrasted€with€the€absence€ofÏcorrelations€between€field€and€greenhouse€DS€(Torto€et€al.,€1996;ÏHartman,€Gibson,€and€Lightfoot,€unpublished).€Stephens€et€al.,Ï(1993)€found€a€correlation€between€field€and€greenhouse€DS€amongÏ12€cultivars€that€contrasted€strongly€for€SDS€field€response€butÏtheir€greenhouse€DS€was€significantly€higher€than€field€DS€due€toÏthe€higher€inoculum€rate€in€the€root€zone.€Among€the€ExFÏrecombinant€inbred€lines€disease€severity€at€the€high€inoculumÏrate€did€not€correlate€with€any€of€the€field€disease€parameters.ÏTherefore,€inconsistencies€between€field€and€greenhouse€responsesÏmay€be€caused€by€high€inoculum€rates€in€greenhouse€assays.Ìà  àThe€low€inoculum€rate€treatment€caused€more€variabilityÏamong€genotype€groups€as€indicated€by€analysis€of€variance€(TableÏ2),€group€means€(Table€3),€individual€line€means€(Table€4),€andÏcorrelation€coefficients.€The€low€inoculum€rate€provided€SDSÏdisease€severity€values€only€35€to€60%€greater€than€field€values.ÏThe€moderate€inoculum€rate€was€partly€effective(r€=0.44,€P€=0.02)Ïin€predicting€field€SDS€response€in€the€greenhouse.€However,€meanÏDS€was€2€to€3€times€higher€than€in€the€field.€Therefore,€inoculumÏrates€of€3000€to€5000€spores€per€cmòòòò3óóóó€of€soil€are€recommended.Ð X,¨'6 Ðà  àThe€DS€mean€for€the€resistant€group€(1.9)€was€used€as€theÏvalue€denoting€resistance€in€the€greenhouse.€While€seven€out€ofÏ10€resistant€lines€were€predicted€to€be€resistant€by€theÏgreenhouse€assay,€only€one€out€of€10€susceptible€lines€appearedÏto€be€resistant.€The€partially€resistant€lines€were€predicted€toÏdivide€equally€between€resistant€and€susceptible€classes.€Hence,Ïa€57%€reduction€in€the€number€of€soybean€lines€advanced€can€beÏachieved€by€greenhouse€selection€for€resistance€to€SDS€with€aboutÏ10%€elimination€of€resistant€genotypes€by€error.Ìò òResistance€to€root€infection€by€òòFusarium€solanióóó óÐ è8  Ðà  àIn€one€experiment€recombinant€inbred€lines€transplanted€ontoÏsoil€infested€with€2,000€òòF.€solanióó€spores€per€gram€in€theÐ Ø( Ðgreenhouse€did€not€produce€SDS€leaf€symptoms€within€28€daysÏsuggesting€the€inoculum€rate€was€too€low€to€cause€scorch.ÏHowever,€òòF.€solanióó€root€infection€severity€(IS)€measured€asÐ @ Ðcolony€forming€units€(CFU)€per€gram€of€dry€root€weightÏsignificantly€correlated€with€disease€severity€from€the€lowÏinoculum€rate€of€the€previous€two€experiments€(r€=0.37,€P€ðð0.05).Ð ¨ø" ÐThe€CFU€means€of€SDS€susceptible€group€(1,324)€was€significantlyÏhigher€than€on€both€the€partially€resistant€(598)€and€theÏresistant€(400)€groups€consistent€with€the€disease€severity€atÏthe€low€inoculum€rate€of€two€experiments€that€produced€SDS€leafÏsymptoms.€Therefore,€IS€may€be€effective€in€separating€resistantÏfrom€susceptible€lines€in€the€greenhouse€when€leaf€scorch€wasÏabsent€and€root€resistance€is€segregating€(Njiti€et€al.,€1998;ÏPrabhu€et€al.,€1999).Ìà  àòòF.€›solanióó€colonies€were€not€recovered€from€roots€of€non„Ð à*0&4 Ðinoculated€plants.€Samples€òòF.€solanióó€recovered€from€inoculatedÐ X,¨'6 Ðplants€were€used€to€reproduce€SDS€symptoms€on€greenhouse€grownÏplants€and€so€confirmed€identification€of€the€pathogen.ÌÌò òRobustness€of€the€low€inoculum€rate€Assayó ó€Ð  h Ðà  àIn€a€cultivar€trial,€two€out€of€four€field€susceptibleÏgenotypes€were€significantly€more€susceptible€than€all€six€fieldÏresistant€genotypes.€Three€field€SDS€susceptible€cultivars€showedÏsignificantly€(Pðð0.05)€higher€SDS€disease€severity€means€thanÐ øH  ÐRipley€when€evaluated€in€the€greenhouse€on€soil€infested€withÏabout€4000€òòF.€solanióó€spores€per€cmòòòò3€óóóó(Table€5).€Among€these€tenÐ è8  Ðcultivars,€greenhouse€DS€significantly€correlated€with€field€DSÏ(r€=0.9)€and€field€DX€(r€=0.86).€Given€that€most€of€theseÏcultivars€are€not€directly€related€to€Essex€and€Forrest€andÏbecause€of€the€diverse€germplasm€they€contain,€we€conclude€thatÏthe€low€òòF.€solanióó€inoculum€rate€greenhouse€assay€can€select€forÐ @ Ðfield€SDS€resistance€by€leaf€scorch€in€many€genetic€backgrounds.€Ìà  àThe€assay€described€above€will€allow€for€multiple€cycles€ofÏtesting€per€season€and€reduce€the€time€to€both€produce€and€verifyÏnew€resistant€cultivars€(Schmidt€et€al.,€1999).€The€assay€willÏreduce€the€costs€of€data€loss€due€to€field€variability€(Prabhu€etÏal,€1999).€Finally,€the€assay€will€facilitate€the€isolation€ofÏSDS€resistance€genes€by€characterization€of€recombinants€duringÏfine€mapping€(Meksem€et€al.,€1999).ÌÌÌÌÌÐ X,¨'6 ЇÒ°ÒÓ´¼Óà@HH' àò òREFERENCESó óˆÐ ° Ðà À àChang,€S.J.C.,€T.W.€Doubler,€V.€Kilo,€R.€Suttner,€J.€Klein,€M.E.ÏSchmidt,€P.T.€Gibson€and€D.A.€Lightfoot.€1996.€Two€additionalÏloci€underlying€durable€field€resistance€to€soybean€suddenÏdeath€syndrome€(SDS).€Crop€Sci.€36:1684„1688.Ìà À 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Ð1070.Ìà À àMeksem€K.,€P.€Pantzapangopolous,€K.€Chancharoenchai,€A.P.Rao„¼Arelli,€and€D.A.€Lightfoot.€1999.€Fine€mapping€proves€theÏbigenic€inheritance€of€resistance€to€soybean€cyst€nematodeÏrace€3.€Molec.€Appl.€Genet.€(In€press).Ð ,`'8 Ðà À àMelgar,€J.,€and€K.W.€Roy.€1994.€Soybean€sudden€death€syndrome:ÏCultivar€reactions€to€inoculation€in€a€controlled€environmentÏand€host€range€and€virulence€of€the€causal€agent.€Plant€Dis.Ï78:265„268.Ìà À àNash,€S.M.€and€W.C.€Snyder.€1962.€Quantitative€estimations€by€plateÏcounts€of€propagules€of€the€bean€root€rot€òòFusariumóó€in€fieldÐ ¸   Ðsoils.€Phytopath.€52:576„572.Ìà À àNjiti,€V.N.€T.W.€Doubler,€R.J.€Suttner,€L.E.€Gray,€P.T.€Gibson,€andÏD.A.€Lightfoot.€1998a.€Resistance€to€soybean€sudden€deathÏsyndrome€and€root€colonization€by€òòFusarium€solanióó€f.€sp.Ð X¨  Ðòòglycinesóó€in€near„isogenic€lines.€Crop€Sci.€38:422:430.Ð À Ðà À àNjiti,€V.N.,€M.A.€Shenaut,€R.J.€Suttner,€M.E.€Schmidt,€and€P.T.ÏGibson.€1998b.€Relationship€between€soybean€sudden€deathÏsyndrome€(SDS)€and€yield€components€in€Fòò6óó„derived€lines.€CropÐ øH ÐSci.€38:673:678.Ìà À àNjiti,€V.N.,€R.J.€Suttner,€L.E.€Gray,€P.T.€Gibson,€and€D.A.ÏLightfoot.€1997.€Rate„reducing€resistance€to€òòFusarium€solanióóÐ 0€  Ðf.€sp.€òòphaseolióó€underlies€field€resistance€to€soybean€suddenÐ ˜è" Ðdeath€syndrome.€Crop€Sci.€37:132„138.Ìà À àNjiti,€V.N.,€M.A.€Shenaut,€R.J.€Suttner,€M.E.€Schmidt,€and€P.T.ÏGibson.€1996.€Soybean€sudden€death€syndrome:€InheritanceÏinfluenced€by€cyst€nematode€resistance€in€Pyramid€x€DouglasÏprogenies.€Crop€Sci.€36:1165„1170.Ìà À àO'Donnell,€K.€and€L.E.€Gray.€1995.€Molecular€tools€for€theÏdetection€and€rapid€identification€of€the€soybean€sudden€deathÏsyndrome€pathogen,€òòFusarium€solanióó€f.€sp.€òòphaseolióó:Ð Ø'(#2 ÐPhylogenetics€and€species€specific€PCR€primers€Molec.€PlantÏMicrob.€inter.€8:709„716.ÌÐ ,`'8 Ðà À àParleviet,€J.E.€1979.€Components€of€resistance€that€reduce€the€rateÏof€epidemic€development.€Ann.€Rev.€Phytopathol.€17:203„222.€ÌÔ‡4XqÜXXXÔà À àPrabhu,€R.€R.,€V.€N.€Njiti,€B.€Bell„Johnson,€J.E.€Johnson,Ô#†XqÜXX4XqÜðh#ÔÔ‡4XqÜXXXqÜÔ€M.E.Ð €Ð ÐSchmidt,€J.H.€Klein,€and€D.€A.€Lightfoot.€1999.€Ô#†XqÜXX4XqÜxi#ÔÔ‡4XqÜXXXqÜÔSelectingÔ‡4¼ŽM¼X4XqÜÔÐ è8 ÐÔ#†4XqÜX¼4¼ŽM,j#Ôsoybean€cultivarsÔ‡4¼ŽM¼X4XqÜÔ€for€dual€resistance€to€soybean€cystÐ P   ÐÔ#†4XqÜX¼4¼ŽM”j#Ônematode€and€sudden€death€syndrome€using€two€DNA€markers.€CropÐ ¸   ÐSci.€39:xxxxÔ#†XqÜXX4XqÜj#ÔÐ  p  Ðà À àRoy,€K.W.€1997.€òòFusarium€solanióó€on€soybean€roots:€Nomenclature€ofÐ ˆØ  Ðcausal€agent€of€sudden€death€syndrome€and€identity€andÏrelevance€of€òòF.€solanióó€form€B.€Plant€Dis.€81:259„266.Ð X¨  Ðà À àRoy,€K.W.,€J.C.D.€Rupe,€D.E.€Hershman,€and€T.S.€Abbey.€1997.€SuddenÏdeath€syndrome€of€soybean.€Plant€Dis.€81:1100„1111.Ìà À àRupe,€J.C.D.,€WE€Sable,€R.T.€Robbins,€and€E.E.€Gbur.€1993.€€SoilÏand€plant€factors€associated€with€sudden€death€syndrome€ofÏsoybean.€J.€Prod.€Agric.€6:218„221.Ìà À àSchmidt,€M.E.,€R.J.€Suttner,€J.H.€Klein,€P.T.€Gibson,€D.A.ÏLightfoot,€and€O.€Myers,€Jr.€1999.€Registration€of€LS„G96Ïsoybean€gerplasm€resistant€to€soybean€sudden€death€syndromeÏand€soybean€cyst€nematode€race€3.€Crop€Sci.€39:598.Ìà À àSmith,€T.J.,€and€H.M.€Camper.€1973.€€Registration€of€Essex€soybean.ÏCrop€Sci.€13:495.Ìà À àStephens,€P.A.,€C.D.€Nickell,€and€F.L.€Kolb.€1993a.€GeneticÏanalysis€of€resistance€to€òòFusarium€solanióó€in€soybean.€PlantÐ  #ð, ÐCrop€Sci.€33:929„930.Ìà À àStephens,€P.A.,€C.D.€Nickell,€C.K.€Moots€and€S.M.€Lim.€1993b.ÏRelationship€between€field€and€greenhouse€reaction€of€soybeanÏto€òòFusarium€solanióó.€Plant€Dis.€77:163„166.Ð @)$4 ÐÌÐ ,`'8 Ðà À àTooley,€P.W.€and€C.R.€Grau.€1982.€Identification€and€quantitativeÏcharacterization€of€rate„reducing€resistance€to€òòPhtophthoraÐ h Ðmegasperma€óóf.€Sp.€òòglycineaóó€in€soybean€seedlings.€Phytopath.Ð €Ð Ð72:727„733.€€Ìà À àTorto,€G.A.,€V.€Njiti€and€D.A.€Lightfoot.€1996.€Loci€underlyingÏresistance€to€sudden€death€syndrome€and€òòFusarium€solanióó€inÐ ¸   Ðfield€and€greenhouse€assays€do€not€correspond.€SoybeanÏGenetics€Newsletter€23:163„166.Ìà À àWrather,€J.A.,€T.R.€Anderson,€D.M.€Arsyad,€J.€Gai,€L.D.€Ploper,€A.ÏPorta„Puglia,€H.H.€Ram,€and€J.T.€Yorinori.€1997.€SoybeanÏdisease€loss€estimates€for€the€top€10€producing€countries€inÏ1994.€Plant€Dis.€81:107„110.€Ìà À àÐ  à ÐÒ°ÒÑ e ÑÑ€7ÙÑÓ=€5qÜ5XÐXd5XÐXd=ÓÑ7€qÜXXdÔXXdÔ7ÑÓ¼´ÓTable€3.€Comparison€of€SDS€disease€severity€(DS)€means€among€SDSÐ ° Ðresistance€groups€within€and€across€inoculum€rates€in€theÏgreenhouse.Ìòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ  h Ѐ€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€DS€means€atÌÓ*ÿÿX°h€°œX*ÓField€SDSà h àòò€€€€€€€€€inoculum€rates€€€€€€€€óóÐ  X  Ðresponse€groupð'ðà h àLowð(ðà € àModerateð(ðà  àHighððÐ € Ð  Ðà h àN=40à € àN=40à  àN=20Ð øH  Ðòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ pÀ  ÐResistantà h à1.9€Aðð€að'ðð'ðà € à3.7€A€bà  à7.3€A€cÐ è8  ÐPartial€resistantà h à1.9€A€€aà € à3.8€A€bà  à6.7€A€cÐ `° Ðsusceptibleà h à3.4€B€€aà € à4.5€A€bà  à7.4€A€cÐ Ø( ÐMean€DS€à h à2.4€à € à4.0€à  à7.1€Ð P  Ðòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ È Ðð'ð€SDS€groups€based€on€disease€index€data€from€five€fieldÏenvironments.Ìð(ð€Means€based€on€two€runs€of€the€experiment.Ìðð€Means€based€on€one€run€of€the€experiment.Ìðð€Means€in€the€same€column€followed€by€the€same€upper€case€letterÏare€not€significantly€different€at€P=<0.05.Ìð'ðð'ð€Means€in€the€same€row€followed€by€the€same€lower€case€letterÏare€not€significantly€different€at€P=<0.05.ÌÌÌÌÌÌÌÐ Ð- )8¨ ЇÓ€ÓÓœ¼ÓTable€4.€Comparison€of€individual€soybean€line€mean€for€diseaseÏseverity€(DS)€at€three€inoculum€rates€in€the€greenhouse€withÏfield€DX,€DS.Ìòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ n¾ ÐÓ6°‚XP ‚àÀp‚8ÿÿ‚Xh€6Óòòà P àóóGH€SDSà  àFld.à À àFld.à p àòò€€€€€Greenhouse€DS€€€€€óóÐ X¨ ÐGenotypeà P àgroupð'ðà  àDXà À àDSà p àlowà ¨ àmoderateà à àhighÐ B ’  Ðòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ , |  Ðò òField€resistant€groupó óÐ  f Ð(ExF)€78à P àRà 0 à€à  à€0.1à À à1.1à p à1.8à ¨ à2.6à à à8.5Ð  P Ð(ExF)€23à P àRà 0 à€à  à€0.5à À à1.1à p à1.3à ¨ à3.3à à à7.6Ð ê : Ð(ExF)€59à P àRà 0 à€à  à€0.5à À à1.2à p à1.3à ¨ à3.1à à à7.7Ð Ô $  Ð(ExF)€67à P àSà 0 à€à  à€1.1à À à1.2à p à2.8à ¨ à3.4à à à8.7Ð ¾  Ð(ExF)€57à P àRà 0 à€à  à€1.1à À à1.3à p à1.9à ¨ à4.7à à à8.6Ð ¨ø  Ð(ExF)€44à P àSà 0 à€à  à€1.1à À à1.3à p à2.7à ¨ à3.3à à à6.5Ð ’â  Ð(ExF)€20à P àRà 0 à€à  à€1.2à À à1.2à p à1.2à ¨ à3.3à à à7.5Ð |Ì  Ð(ExF)€47à P àSà 0 à€à  à€1.5à À à1.2à p à3.0à ¨ à5.4à à à6.5Ð f¶  Ð(ExF)€37à P àRà 0 à€à  à€1.9à À à1.2à p à1.4à ¨ à4.0à à à3.1Ð P   Ð(ExF)€55à P àRà 0 à€à  à€3.0à À à1.1à p à1.9à ¨ à4.5à à à7.9Ð :Š" Ðò òField€partially€resistant€groupó óÐ $t$ Ð(ExF)€46à P àRà 0 à€à  à€5.4à À à1.4à p à1.5à ¨ à3.7à à à6.7Ð ^& Ð(ExF)€14à P àSà 0 à€à  à€6.3à À à1.3à p à3.4à ¨ à3.4à à à8.2Ð øH( Ð(ExF)€91à P àRà 0 à€à  à€6.4à À à1.3à p à1.3à ¨ à2.6à à à4.2Ð â2* Ð(ExF)€75à P àSà 0 à€à  à€6.4à À à1.4à p à2.0à ¨ à4.6à à à8.4Ð Ì, Ð(ExF)€49à P àSà 0 à€à  à€6.9à À à1.3à p à1.8à ¨ à2.9à à à7.6Ð ¶. Ð(ExF)€26à P àRà 0 à€à  à€7.2à À à1.4à p à1.4à ¨ à3.9à à à5.5Ð  ð0 Ð(ExF)€€6à P àRà 0 à€à  à€8.2à À à1.5à p à1.2à ¨ à3.8à à à5.1Ð ŠÚ2 Ð(ExF)€73à P àSà 0 à€à  à€8.6à À à1.5à p à2.2à ¨ à4.1à à à6.3Ð tÄ4 Ð(ExF)€97à P àSà 0 à€à  à€9.1à À à1.4à p à2.5à ¨ à3.0à à à7.0Ð ^®6 Ð(ExF)€45à P àRà 0 à€à  à€9.7à À à1.4à p à1.9à ¨ à4.8à à à8.2Ð H˜8 Ðò òField€SDS€susceptible€groupÐ 2‚: Ðó óš(ExF)€39à P àS€à 0 à€à  à15.7à À à2.3à p à3.2à ¨ à3.4à à à6.1Ð  l< Кš(ExF)€51à P àSà 0 à€à  à16.0à À à2.0à p à2.5à ¨ à4.6à à àš7.9Ð !V> К(ExF)€10à P àS€à 0 à€à  à17.5à À à2.0à p à4.4à ¨ à4.4à à àš8.3Ð ð!@@ К(ExF)€68à P àRà 0 à€à  à18.2à À à2.1à p à1.9à ¨ à3.9à à àš8.1Ð Ú"*B К(ExF)€18à P àSà 0 à€à  à18.6à À à2.1à p à4.1à ¨ à2.5à à àš8.3Ð Ä#D К(ExF)€83à P àSà 0 à€à  à18.7à À à1.9à p à3.5à ¨ à5.4à à àš8.5Ð ®$þF К(ExF)€76à P àSà 0 à€à  à18.7à À à2.3à p à3.0à ¨ à4.1à à àš7.8Ð ˜%è H К(ExF)€85à P àSà 0 à€à  à19.8à À à2.3à p à4.9à ¨ à5.7à à àš5.9Ð ‚&Ò!J К(ExF)€80à P àSà 0 à€à  à20.2à À à2.1à p à3.6à ¨ à4.9à à àš6.0Ð l'¼"L Ð(ExF)€€7à P àSà 0 à€à  à20.3à À à2.2à p à3.2à ¨ à5.9à à à7.4Ð V(¦#N Кšòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ @)$P Ðð'ð€SDS€resistance€group€based€on€greenhouse€disease€severity€atÏlow€inoculum€rate€(R=SDS„resistant€and€S=SDS„susceptible).ÌÌÌÐ Ò-")Z ÐÓ€ÓÓËœÓTable€5.€Comparison€of€SDS€disease€severity€on€ten€soybeanÏcultivars€following€seedling€inoculation€by€òòFusarium€solanióó€atÐ F– Ðlow€inoculum€rate€(about€4000€spores€per€cmòòòò3óóóó€of€soil)€in€theÐ Ü, Ðgreenhouse.ÌòòÓ3°‚XhȰ‚XP ‚àÀp‚83Ó€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ  X ÐÓ*°‚X‚°‚Xh` *Ó€à  àField€DXà  àField€DSà  àGreenhouse€DSÐ ž î  Ðòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ 4„  ÐRipleyà  à€1.6à  à1.09à  à1.40Ð Ê  ÐPI€520.733à  à€0.2à  à1.15à  à1.52Ð `°  ÐJackà  à€1.5à  à1.10à  à1.83Ð öF ÐManokinà  à€1.8à  à1.09à  à1.90Ð ŒÜ ÐHartwigà  à€0.6à  à1.12à  à2.20Ð "r ÐHamiltonà  à€2.2à  à1.15à  à2.54Ð ¸ ÐSpencerà  à33.3à  à2.72à  à2.78Ð Nž ÐA5403à  à18.0à  à2.10à  à3.20Ð ä4 ÐCM497à  à30.1à  à3.01à  à4.40Ð zÊ ÐFlyerà  à35.7à  à3.06à  à4.90Ð `  Ðò òLSD€(ðð€=0.05)à  à13.1à  à1.11à  à1.53ó óÐ ¦ö" Ðòò€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€€óóÐ