Abstract:
TheqTSN4wasidentifiedasriceQTL(QuantitativeTraitsLocus)increasingtotalspikeletnumberperpanicleandflagleafareabutpotentiallyreducingpaniclenumberdependingontheenvironment.Sofar,thistrade-offwasmainlyobservedatgrainmaturityandnotspecificallystudiedindetails,limitingtheapprehensionoftheagronomicinterestofqTSN4.ThisstudyaimedtounderstandtheeffectofqTSN4andoftheenvironmentonpaniclesizing,itstrade-offwithpaniclenumber,andfinallyplantgrainproduction.ItcomparedtwohighyieldinggenotypestotheirNearIsogenicLines(NIL)carryingeitherQTLqTSN4orqTSN12,twodistinctQTLscontributingtotheenlargedpaniclesize,thereafterdesignatedasqTSN.TraitsdescribingCsink(organappearancerate,size,biomass)andsource(leafarea,photosynthesis,sugaravailability)weredynamicallycharacterizedalongplantand/orpanicledevelopmentwithintwotrials(greenhouse,field),eachcomparingtwotreatmentscontrastingforplantaccesstolight(withorwithoutshading,highorlowplantingdensities).ThepositiveeffectofqTSNonpaniclesizeandflagleafareaofthemaintillerwasconfirmed.Moreprecisely,itcouldbeshownthatqTSNincreasedleafareaandinternodecross-section,andinsomecasesofthephotosyntheticrateandstarchreserves,ofthetop3–4phytomersofthemaintiller.Thiswasaccompaniedbyanearliertilleringcessation,thatcoincidedwiththeinitiationofthesephytomers,andanenhancedpaniclesizeonthemaintiller.PlantleafareaatfloweringwasnotaffectedbyqTSNbutfertiletillernumberwasreducedtoanextentthatdependedontheenvironment.Accordingly,plantgrainproductionwasenhancedbyqTSNonlyundershadinginthegreenhouseexperiment,wherepaniclenumberwasnotaffectedandphotosynthesisandstarchstorageininternodeswasenhanced.TheeffectofqTSNonricephenotypewasthusexpressedbeforepanicleinitiation(PI).Whetherearlytilleringreductionororganoversizingatmeristemlevelisaffectedfirstcannotbeentirelyunraveled.FurtherstudiesareneededtobetterunderstandanysignalinvolvedinthisearlyregulationandtheqTSN×Environmentinteractionsunderlyingitsagronomicinterest.
