MutationsBreedinginRabiSorghum[Sorghumbicolor(L.)Moench] forcreationof Genetic Variability and Association Studies onMorpho-Physiological Traits in InducedMutants.

Abstract

Sorghum(Sorghumspp.) isagloballysignificantcereal,yet itsproductivityinIndia,particularlyforrabi
sorghum, isconstrainedbylowandhighlyvariableyields,primarilyduetopost-floweringdroughtstress
[1] [2]. This comprehensive investigationwas undertaken to generate and assess desirable genetic
variability intherabi sorghumgenotypeTSG-98(Muguthi) through inducedmutagenesisusingelectron
beamirradiation.Pureselfedseedsweretreatedwithfivedosesof10MeVelectronbeam(100Gy,200
Gy,300Gy,400Gy,and500Gy)andsubsequentlyevaluatedacrosstheM1andM2generations.Thestudy
focused on threemain areas:mutagenic sensitivity inM1, the frequency and spectrumof induced
mutations inM2, andtheextent of geneticvariability, heritability, correlation, andpathanalysis for
fourteencriticalyieldandyield-contributingcharacters.
ResultsfromtheM1generationdemonstratedacleardose-dependentreductioninseedgerminationand
plantsurvival,acommonindicatorofmutagenicsensitivity[3] [4].Thelethaldosefor50%germination
(LD50)waspreciselyestimatedat258.5Gy,suggestingthatthedoserangebetween200Gyand300Gyis
optimal formaximizingmutationfrequencywhilemaintainingamanageablesurvival rateforsubsequent
generationstudies. IntheM2generation,thefrequencyofchlorophyllmutations increasedlinearlywith
thedose,peakingat3.461%at500Gy.Thespectrumof chlorophyllmutants includedalbina, xantha,
viridis,xanthaviridis,andchlorina,withchlorinabeingthemostprevalent type.Analysisofmutagenic
effectivenessandefficiency indicatedthat lowerdoses (100Gyand200Gy)weresuperior, yieldinga
higherproportionofmutationsrelativetoundesirableeffectslikepollensterility[5].
Awideandvaluablespectrumofviablemutationswas isolated, includingsemi-dwarf,ultra-dwarf,early
maturing (103days),boldseeded(4.5-4.9g100-seedweight),and largeearheadtypes,all possessing
significantpotential for crop improvement.Analysisof varianceconfirmedthesuccessful inductionof
highlysignificantgeneticvariabilityforall fourteenquantitativecharactersstudied.Highgenotypicand
phenotypiccoefficientsof variation (GCVandPCV)wereobservedfor traits suchas Fodder yieldper
plant,Flag leafarea,andLeafarea, indicatingastronggeneticbasis for thesetraits.Crucially,Grain
yieldperplant,Primariesperpanicle,Fodderyield,andFlagleafareaexhibitedhighheritabilitycoupled
withhighgeneticadvanceasapercentageofmean(GAM), confirming thatdirect selectionfor these
traitswouldbehighlyeffective[6].
Correlationstudiesrevealedapositiveandsignificantgenotypicandphenotypicassociationofgrainyield
perplantwithdaysto50%flowering,daystomaturity,primariesperpanicle,paniclelength,fodderyield
perplant, flag leafarea,and leafarea.Pathcoefficientanalysis furtherdissectedtheseassociations,
identifyingDaysto50%flowering,Primariesperpanicle,Grainsperprimary,Paniclelength,Fodderyield,
Relativewatercontent(RWC),andChlorophyllcontent(SPAD)ashavingadirectpositiveeffectongrain
yieldperplant.Thesefindingsprovidearobustframeworkforselectingsuperiormutantlines.Thestudy
successfullygeneratedandcharacterizedadiversepoolofgeneticresources,whichcanbeimmediately
utilized intargetedsorghumbreedingprograms todevelophigh-yielding,drought-resilientcultivars for
therabiseason