Research and Application of Biocontrol of Plant Diseases and PGPR in Chinacountry report.docx

Research and Application of Biocontrol of Plant Diseases and PGPR in Chinacountry report.docx

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ResearchandApplicationofBiocontrolofPlantDiseasesandPGPRinChinacountryreport

In：

A.Ogoshi,etal,eds.,PlantGrowth-PromotingRhizobacteria-PresentStatusandFutureProspects.Pp2-9.NakanishiPrinting,Sapporo.

CountryReport

ResearchandApplicationofBiocontrolofPlantDiseasesandPGPRinChina

TangWenhuaYangHetong

Dept.ofplantPathology,ChinaAgriculturalUniversity,Beijing,100094,P.R.China

Summary.ResearchonbiocontrolofplantdiseaseshasbeenstartedinChinasinceearly1950's.5406actinomyceswasarepresentativeofantagonistswhichwasusedasanagentforbiocontrolofrootandwiltdiseasesofcotton.Since1970's,muchworkonbiologicalcontrolofsoil-borneplantpathogenshasbeendone.TheresearchonPGPRstartedinthisperiod.In1980s,muchresearchhasbeendoneonBacillusspp..'YIB'wasanexampleofPGPRwhichwasusedonalargescaleinChina.Sincethen,theresearchonbiocontrolandPGPRincreasedsharply.Itincludedscreeningantagonistsandbeneficialmicroorganismstargeteddifferentdiseases,mainlysoil-borneplantpathogens;evaluatingeffectivenessofdiseasecontrolingreenhouseandfield.Someofthemhavebeendemonstratedinfieldinaquitelargearea.Sofar,twostrainsofTrichodermaspp.,onestrainsofBacillussubtilis,andonestrainofPseudomonascepaciawereregisteredascommercialproducts.Somenewnaturalbiocontrolphenomenonhavebeenfound.ResearchesonecologyandmodeofactionofbiocontrolagentsandPGPRarebeingconducted.Inordertoincreaseeffectiveness,researchonimprovementofbiocontrolagentsandPGPRbygeneticengineeringisgoingontheway.SomeobstaclesfordevelopingbiocontrolofplantdiseasesandPGPRarediscussed.Integratedbiocontrolsystemshouldbeconsidered.

Introduction

Chinesefarmerspracticedcroprotationandapplicationofmanureabout5,000yearsago,andtheybeganirrigationabout3,000yearsago.InthefirstcenturyB.C.,farmerswereadvised,'ifafieldgavepoorcropinthesecondyear,fallowitforoneyear'.Thatstartedatraditional'organic'agriculturalsystem.Itisreasonabletobelievethatthecroprotationandmanureapplicationgavebiologicalcontrolviamicroorganismsinvolvedagainstsoil-bornepathogensthatwouldreducecropproduction.Inmodernagriculture,croprotationwasdifficulttoconductforlandlimitation,andtherefore,chemicalfungicidewasintroducedintoagriculturesystem.Thechangeshavebroughtaseriesofproblems:

（1）Environmentpollution;

（2）Pathogenresistance,resurgenceandchemicalresidue;（3）Difficultyincontroldiseaseswithexistingmethods,suchasresistantcultivars,chemicalfungicides,ecologicaladjustment,etc.ThisledtothebeginningofbiologicalcontrolresearchinChina.In1954,aSteptomycesjingyangensisstrain,whichwasdesignatedas5406,wasisolatedfrom4,000isolatesofactinomycesinthecotton/alfalfafields（Liang,etal,1993）.Sincethen,thisstrain,'5406antagonist'or'5406Cytokinin',hasbeenappliedto6millionhectaresofcottonforsuccessfulcontroloftheseedlingdiseasescausedbyRhizoctoniaandthewiltdiseasescausedbyVerticilliumalbo-atrumoverthelast30years（Liang,etal,1993）.Fromthenon,extensiveandintensiveworkhasbeendoneonisolationandscreeningofactinomycesantagonists.Becauseofthepoorproliferationandlowgrowthrateoftheseactinomyces,theapplicationofthelivingorganismsasbiocontrolagentsdidnotgainmuchprogress,therefore,themainintereststurnedtoantibioticsproducedbySteptomycesspp.Jingangmycin,aproductofStreptomyceshygroscopicusvar.jingangensisisolatedbytheShanghaiPesticideInstitute,hasbeeneffectivelyappliedinthecontrolofsheathblightofriceoverthelasttwodecades（Shen,etal,1993）.The'120'product,producedbyS.hygroscopicusvar.beijingensisisnowwidelyusedinthecontrolofcerealandvegetablediseasessuchaspowderymildewofwheatandFusariumwiltofwatermelonandcucumber（JianfengChen,etal,1993）.However,difficultiesinprocessingantibioticproductswithlowcostandeaseforpathogenstodevelopresistancewerethemainobstaclesforfastdevelopmentofantibioticsbothinprocessingandapplication.Presenttendencyistodeveloplivingmicrobialbiocontrolagentsbothinresearchandproductextension.Muchprogresshasbeenachievedinthelast20years,severalformulationscontaininglivingmicroorganismshavebeencommercializedandregisteredagainstplantdiseases（GuBaogen,1996）.TheemphasisofthisreviewisonthemicrobialbiocontrolagentsconsistedoflivingorganismsrelatedtoplantdiseasemanagementinChina.

1.Strategiesinvolved

1.1Inhibitingpathogenpopulationwithmicrobes

Biocontrolagentsinhibitgrowthofpathogenpopulationstodifferentlevels,bywaysofthemultiplication,introductionandapplicationsofantagonistsintospermosphere,phylloplane,rhizosphereandtherhizoplaneofplants.Antagonistsinvolvedarediversified,bacteriocin-producingbacteria（Yang,etal,1993）,avirulentstrainsofpathogensandmicrobialsaprophytesaregenerallyintroducedtoinhibitpathogenpopulationgrowth.

1.2Enhancementofbeneficialmicrobegrowth

'Naturalbiologicalcontrol'areexistinginplantdiseasemanagementallthetime.Becauseofthevarioustypeofcompetitionsamongmicrobes（includeneutral,harmful,beneficialrelationships）,naturallyexistingbeneficialmicroorganismscanbeenhancedtoalevelthatwouldcontrolplantpathogensviadifferentmethods,suchasapplicationofgreenmanures,adjustingthemacro-andmicro-ecologicalenvironment,croprotation,increaseandmultiplicationofsaprophytes,facilitatingmicrobialoccupationofthemicro-spaceinandaroundtheplant,strengtheningcompetitionfornutrientsbetweensoilmicroorganismsandplantpathogens（CaiYinjie,1996）.

1.3Promotionofhealthyplantgrowthandinducementofplantresistanceand/orselfdefenseagainstpathogen

Severalmethodswereemployedtostimulatetheinnerdefensemechanismsagainstplantpathogens,includingplantgrowthpromotingrhizobacteria（PGPR）,crossprotection,immunizationandvirusresistanceviacoatproteingenes.（TangWenhua,1993,Luo,etal,1996,Guo,etal,1996）

2.Antagonistsandtargetpathogensinvolved

2.1Bacteria

Pseudomonas,Bacilluswerethemostcommonlyusedmicrobesinbiocontrolresearchandapplication.IngenusPseudomonas,P.fluorescens,P.putida,P.solanacearum（avirulentbacteriocin-producingstrains）,andingenusBacillus,B.subtilis,B.cereus,B.pumillus,B.licheniformis,B.macerans,B.polymixa,B.coagulansweretheprincipalresearchedmembers（ChenYu,etal,1996,ChenMingyuan,etal,1996,MaPing,etal,1996,PengYufa,etal,1996,TangWenhua,etal,1996,WangJinsheng,etal,1996,XiaZhengjun,etal,1996,XuHongqingetal,1996,Zhang,etal,1996）.OthergeneraofbacteriainvolvedwereErwinia,Agrobacterium,andSerratia,Alcaligensfaecalis（Songwei,etal,1996）ect.AXanthomonascampestrispv.oryzaestrainwasdisarmedandwasemployedinthecontrolofbacterialleafblightofricecausedbythepathogen.Whenthedisarmedstrainwassprayedontheleavesofriceasasuspension,itreducedthediseaseseveritybyabout60%andincreasedtheyieldby4.6-19%.

2.2Fungi

Trichoderma,Gliocladium,Fusarium,Verticillium,Penicillium,Coniothyrium,Phialophora,PythiumandseveralotherfungiweregenerallyemployedinbiocontrolresearchandapplicationagainstplantpathogensasBotrytis,Fusarium,Rhizoctoniaetc（SongJiahua,etal,1996,ZhangBingxin,1993,WangDaoben,etal,1996,TangWenhua,1993,ChenMingyuan,etal,1996,Shi,etal,1996,WangWei,etal,1996）.SeveralstrainsofTrichodermaspp.havebeenregisteredinChinaagainstdownymildewofvegetablesandgraymoldofgreenhouse-grownvegetables,theformulationsarenowbeingappliedinavastrangealloverChina（GuBaogen,1996,YangHetongetal,1996）.Vesicular-arbuscularmycorrhizalfungiisalsoconsideredinbiocontrolofplantdiseasesatpresent（LiuRunjin,andYinXiSheng,1996）,themechanismsinvolvedisresistancesubstancesinduction.Avirulentplantpathogenswerealsoemployedinbiocontrolresearch（LiHonglianetal,1996）.

2.3Actinomyces

Streptomyceswerethemaingroupdirectlyrelatedtothebiocontrolofplantpathogens.Usually,Steptomyceswerestudiedfortheirantibioticproduction,butatpresent,endophyticStreptomyceswithincottonplantwhichwasinhibitorytoRhizoctoniasolani,Fusariumoxysporumf.sp.vasinfectumandVerticilliumdahliaewereobtainedinourgroupandshowedpromisingresultsincontrollingthepathogensingreenhousetests（LiuShufen,andTangWenhua,1996,LiuDaqunetal,1996）.

2.4Virus

CMVandTMVandthesatelliteviruswerethemaininterestedonesinbiologicalcontrolresearch.TMVts（TMVthatinfectstomato）strainwasmutationedbychemicalmethodtohypovirulentonesamongwhichN14waschosentocontrolTMVontomato.SatelliteRNA-freeCMVstrainL871whichwashypovirulentwasonceemployedtocontrolCMVontomato.CMV-S51andS52wereobtainedbycombiningSatelliteRNAwithtomatoCMVandreduceddiseaseseverityby50%andincreasedyieldby30%whenusedtocontrolCMVongreenpepperandtomato（Tianwenhui,etal,1996）.

3.Mechanisms

Antagonistscanreduceplantdiseasesbyvariousmechanisms.Understandingofthesemechanismswouldprovideinformationonhowtoimproveantagonistsandtoapplythemreasonablytogethighereffectiveness.Amongallpossiblemechanisms,antibiosis（TangWenhua,1992,LiuRuijunetal,1996）,nutrientandspacecompetition,（WangChunxiaetal,1996,Zhang,etal,1996）lysis（WangYimin,1995,Proceedingsof1991,1995）,mycoparasitism（So