Genetic variation of temperature-regulated curd induction in cauliflower: elucidation of floral transition by genome-wide association mapping and gene expression analysis

Cauliflower(Brassicaoleraceavar.botrytis)isavernalization-responsivecrop.Highambienttemperaturesdelayharvesttime.Theelucidationofthegeneticregulationoffloraltransitionishighlyinterestingforapreciseharvestschedulingandtoensurestablemarketsupply.Thisstudyaimsatgeneticdissectionoftemperature-dependentcurdinductionincauliflowerbygenome-wideassociationstudiesandgeneexpressionanalysis.Toassesstemperature-dependentcurdinduction,twogreenhousetrialsunderdistincttemperatureregimeswereconductedonadiversitypanelconsistingof111cauliflowercommercialparentlines,genotypedwith14,385SNPs.Broadphenotypicvariationandhighheritability(0.93)wereobservedfortemperature-relatedcurdinductionwithinthecauliflowerpopulation.GWAmappingidentifiedatotalof18QTLlocalizedonchromosomesO1,O2,O3,O4,O6,O8,andO9forcurdingtimeundertwodistincttemperatureregimes.Amongthose,severalQTLarelocalizedwithinregionsofpromisingcandidatefloweringgenes.Inferringpopulationstructureandgeneticrelatednessamongthediversitysetassignedthreemaingeneticclusters.Linkagedisequilibrium(LD)patternsestimatedglobalLDextentofr2=0.06andamaximumphysicaldistanceof400kbforgeneticlinkage.TranscriptionalprofilingoffloweringgenesFLOWERINGLOCUSC(BoFLC)andVERNALIZATION2(BoVRN2)wasperformed,showingincreasedexpressionlevelsofBoVRN2ingenotypeswithfastercurding.However,functionalrelevanceofBoVRN2andBoFLC2couldnotconsistentlybesupported,whichprobablysuggeststoactfacultativeand/ormightevidenceforBoVRN2/BoFLC-independentmechanismsintemperature-regulatedfloraltransitionincauliflower.Geneticinsightsintemperature-regulatedcurdinductioncanunderpingeneticallyinformedphenologymodelsandbenefitmolecularbreedingstrategiestowardthedevelopmentofthermo-tolerantcultivars.