Bt corn plants and their straw have no apparent im

REGULARARTICLEBtcornplantsandtheirstrawhavenoapparentimpactonsoilmicrobialcommunitiesFengxiaoTan&JianwuWang&YuanjiaoFeng&GuoliangChi&HailanKong&HuifengQiu&SulingWeiReceived:7April2009/Accepted:1September2009/Publishedonline:23September2009#SpringerScience+BusinessMediaB.V.2009AbstractPolymerasechainreaction–denaturinggradientgelelectrophoresis(PCR–DGGE)andsequencesofthe16Sand18SrRNAgeneswereusedtoaccesstheeffectsofactivelygrowingBacillusthuringiensis(Bt)cornPioneer34B24andNongda1246*1482,andplantstraw(leavesplusstalks)ofBthybridPioneer34B24andNongda61onsoilbacterialandfungalcommunities.Two-wayindicatorspeciesanalysis(TWINSPAN®),anddetrendedcorrespondenceanalysis(DCA)oftheDGGEdataindicatedthatneithertheactivelygrowingBtcornnoritsstrawhadanyconstantapparenteffectonthesoilbacteriaandfungicommunitystructure.Theageofthegrowingplants,orthetimingofplantstrawdecompositionmayhavemoreeffectonthemicrobialcommunitythanotherfactors,i.e.,thepresenceofCryprotein,planthybridandvariety.KeywordsBtcorn.Microbialcommunity.PCR-DGGE.Rhizospheresoil.PlantresidueIntroductionGeneticallymodified(GM)cropplantsforresis-tancetopestsrepresentapotentialpromisingtoolwithwhichtodecreasetheamountofchemicalpesticidesusedinagriculture.Cry-proteinsfromBacillusthuringiensis(Bt)arebyfarthemostcommoninsecticidalproteinsthathavebeenengi-neeredintoplants.Btcrygeneshavebeenengi-neeredintoalargenumberofplantspecies,suchascorn,cotton,potato,tomato,eggplant,rice,etc.(see,e.g.,Icozetal.2008;Sanvidoetal.2007).Btcornisgrownonabout11.3millionhaworldwideandis,byfar,themostwidelygrownBtcropintheworld(James2005).The“firstgeneration”CryproteinsengineeredintocornwereCry1Ab,andCry9C.Monsanto’sYieldGard®corn,transformationeventMON810,expressingCry1Abtoxictosomelepi-dopteraninsectpests,isthemostwidelygrownBtcroptoday(BenedictandRing2004;IcozandStotzky2008).PlantSoil(2010)329:349–364DOI10.1007/s11104-009-0163-2ResponsibleEditor:JuhaMikola.FengxiaoTanandJianwuWangcontributedequallytothiswork.F.Tan:J.Wang:Y.Feng:G.Chi:H.Kong:H.Qiu:S.WeiKeyLaboratoryofEcologicalAgricultureofMinistryofAgricultureofChina,KeyLaboratoryofAgroecologyandRuralEnvironmentofGuangdongRegularHigherEducationInstitutions,SouthChinaAgriculturalUniversity,Guangzhou510642,People’sRepublicofChinaJ.Wang(*)DepartmentofEcology,CollegeofAgriculture,SouthChinaAgriculturalUniversity,Guangzhou510642,Chinae-mail:[e-mail],Btcornhasnotyetbeenapprovedforcommercialcultivation,althoughevaluationoftheenvironmentalriskofsomereleasedBtcornhybrids[e.g.,Pioneer34B24(Mon810)fromMonsanto,expressingCry1Abtoxin,andNongda61andNon-gda1246*1482fromChinaAgriculturalUniversity,expressingCry1Aprotein]intheNorthEastPlainandNorthChinaPlainhaslastedformorethan10years(1998–2008).TheaimofintroducingBtcorntoChinaistocontrolthedamageofAsiancornborerOstriniafurnacalis(Guenee)andreducepesticideinputincornproduction.ThedelayedcommercialintroductionofBtcorninChinaresultsmainlyfromthefollowing:firstly,cultivatingBtcornmayleadtodevelopmentofresistanceofthetargetpests(i.e.,Ostriniafurnacalis[Guenee]andHelicoverpaarmi-gera[Hubner])ofBtcotton.TheNorthEastandNorthChinaPlainsarethemaincultivatedBtcottonbelt,aswellasbeingthemostsuitableregionforcorncultivationinChina.By2006,Btcottonhadbeengrownintensivelyineverycotton-growingarea,andhadreached4millionha,accountingfor70%ofthetotalgrowingarea(Wu2007).TheconventionalcornfieldsintheseregionshadprovidedanaturalrefugeformanagementoftheresistancetoBtcottonbyH.armigera(Hubner).Secondly,thereleaseofBtcornremainsalong-termconcernbecauseofthepresumedpotentialecologicalandenvironmentalrisks,e.g.,effectsonnon-targetorganisms,effectsonsoilecosystems,etc.(Icozetal.2008;Saxenaetal.2004;Sanvidoetal.2007).Todate,laboratoryandfieldstudieshavedemon-stratedthatCryproteinexpressedinBtcornentersthesoilsystemmainlyviarootexudationthroughoutthegrowthoftheplant,inpollenreleasedduringtasseling,andfromcropresiduesafterharvest(e.g.,IcozandStotzky2007;Icozetal.2008;Lehmanetal.2008;Saxenaetal.1999,2002a;SaxenaandStotzky2000;Zscheischleretal.1984;Zwahlenetal.2003).Asatoxin,CryproteinreleasedtosoilfromBtcornhasbeenshowntodegradeslowlyandtoaccumulateinsoil(TappandStotzky1998;Saxenaetal.2002a;Zwahlenetal.2003).OrganismsinsoilwillcomeintocontactwithtransgenicCryproteinswhentheproteinsarereleasedfromBtcorninrootexudatesorfromdecomposingplanttissue,thusposingapoten-tialriskfornontargetorganisms,includingmicro-organisms(e.g.,Icozetal.2008;Saxenaetal.1999;SaxenaandStotzky2000;Zwahlenetal.2003).Whenassessingtheecologicalrisksoftransgenicplants,theirimpactonsoilmicrobesshouldbeconsidered,becausesoilmicrobialcommunitiescarryoutcomplexprocessesthatareofmajorecologicalandagriculturalsignificance(e.g.,forbiogeochemicalcyclesandsoilfertility;Icozetal.2008;Saxenaetal.1999).Anychanges,howeversmall,inthecomposi-tionofthemicrobialcommunityshouldbeconsideredasanearlywarningindicatorforriskassessment.Therehavebeenanumberofstudies,usingdifferentparametersandtechniques,ontheeffectsofBtcornhybridsonthesoilmicrobialcommunity.Moststudies