简介：TocomparethedevelopmentofphysicalcrustsinthreetypicalcultivatedsoilsofChina,ablacksoil(LuvicPhaeozem),aloesssoil(HaplicLuvisol),andapurplesoil(CalcaricRegosol)werepackedinsplashplateswithcoveredanduncoveredtreatments,andexposedtosimulatedrainfall.Meshescoveredabovethesurfacesofhalfofsoilsamplestosimulatetheeffectsofcropresidueoncrusting.Theresultsindicatedaprogressivebreakdownofaggregatesonthesoilsurfaceasrainfallcontinued.Thebulkdensityandshearstrengthonthesurfaceofthethreesoiltypesincreasedlogarithmicallyasrainfalldurationincreased.Duringthefirst30minofsimulatedrainfall,thepurplesoildevelopeda7-8mmthickcrustandtheloesssoildevelopeda3-4mmthickcrust.Theblacksoildevelopedadistinguishable,butstillunstable,crustafter80minofsimulatedrainfall.Soilorganicmatter(SOM)content,themeanweightdiameter(MWD)ofsoilaggregates,andsoilclaycontentwerenegativelycorrelatedwiththerateofcrustformation,whereasthepercentageofaggregatedispersion(PAD),theexchangeablesodiumpercentage(ESP),andthesiltandsandcontentswerepositivelycorrelatedwithcrusting.Mechanicalbreakdowncausedbyraindropimpactwastheprimarymechanismofcrustformationintheblacksoilwithmorestableaggregates(MWD25.0mm,PAD3.1%)andhigherSOMcontent(42.6gkg~(-1)).Slakingandmechanicaleluviationweretheprimarymechanismsofcrustformationinthepurplesoilwithlowclaycontent(103gkg~(-1)),cationexchangecapacity(CEC,228mmolkg~(-1)),ESP(0.60%),andSOM(17.2gkg~(-1)).MechanicalbreakdownandslakingwerethemostimportantintheloesssoilwithlowCEC(80.6mmolkg~(-1)),ESP(1.29%),SOM(9.82gkg~(-1)),andhighPAD(71.7%)andMWD(4.6mm).Simulatedresiduecoverreducedcrustformationinblackandloesssoils,butincreasedcrustformationinpurplesoil.

简介：QTLmappingforsevenqualitytraitswasconductedbyusing254recombinantinbredlines(RIL)derivedfromajaponica-japonicaricecrossofXiushui79/CBao.Theseventraitsinvestigatedweregrainlength(GL),grainlengthtowidthratio(LWR),chalkgrainrate(CGR),chalkinessdegree(CD),gelatinizationtemperature(GT),amylosecontent(AC)andgelconsistency(GC)ofheadrice.ThreemappingmethodsemployedwerecompositeintervalmappinginQTLMapper2.0softwarebasedonmixedlinearmodel(MCIM),inclusivecompositeintervalmappinginQTLIciMapping3.0softwarebasedonstepwiseregressionlinearmodel(ICIM)andmultipleintervalmappingwithregressionforwardselectioninWindowsQTLCartographer2.5basedonmultipleregressionanalysis(MIMR).ResultsshowedthatfiveQTLswithadditiveeffect(A-QTLs)weredetectedbyallthethreemethodssimultaneously,twobytwomethodssimultaneously,and23byonlyonemethod.FiveA-QTLsweredetectedbyMCIM,ninebyICIMand28byMIMR.ThecontributionratesofsingleA-QTLrangedfrom0.89%to38.07%.AlltheQTLswithepistaticeffect(E-QTLs)detectedbyMIMRwerenotdetectedbytheothertwomethods.FourteenpairsofE-QTLsweredetectedbybothMCIMandICIM,and142pairsofE-QTLsweredetectedbyonlyonemethod.Twenty-fivepairsofE-QTLsweredetectedbyMCIM,141pairsbyICIMandfourpairsbyMIMR.ThecontributionratesofsinglepairofE-QTLwerefrom2.60%to23.78%.IntheXiu-BaoRILpopulation,epistaticeffectplayedamajorroleinthevariationofGLandCD,andadditiveeffectwasthedominantinthevariationofLWR,whilebothepistaticeffectandadditiveeffecthadequalimportanceinthevariationofCGR,AC,GTandGC.QTLsdetectedbytwoormoremethodssimultaneouslywerehighlyreliable,andcouldbeappliedtoimprovethequalitytraitsinjaponicahybridrice.