Mapping Of QTLs Controlling Variation In Photoperiod Sensitivity In Maize

Photoperiod sensitivity of tropical maize germplasm has become one of the main limiting factor,which would impact introducing the tropical maize germplasm into temperate regions.Because of the light length extension and higher latitude,often exhibit strong photoperiod sensitivity,result to the performance of vegetative growth,internodes number and leaf number increased,and the reproductive growth was restrained.Therefore,analysis the molecular mechanism of photoperiod response variation of tropical maize,which can reveal the genetic basis of photosensitivity's variation,which would be important for maize germplasm's,improvement and amplication.In this study,one associated panel containing 226 natural maize inbred lines and one bi-parental population derived from Qi319×T32(QT)with 150 F_2:3 families were selected to be materials,where in Qi319 showed weaker photoperiod sensitivity and T32 showed stronger photoperiod sensitivity.Photoperiod sensitivity related traits were evaluated under three environments(long sunshine of Zhang ye,Gansu province and short day of Guizhou Guiyang,and Sanya,Hainan)in one year.Genotypes of these lines were evaluated by using Maize SNP50 chip and GBS method,respectively.Then QTL and QTNs were identified by using GWAS and linkage analysis.The main research results are listed as:1.Phenotypic analysis showed that,phenotypic variation of the 6 photosensitive related traits and their photosensitive index showed significantly different among different traits.Under two light lengths,six photosensitivity-related traits and their photosensitivity indexes showed extremely significant differences between pair-genotypes(P<0.01).Meanwhile,the photosensitive related traits and their photosensitive index of QT population showed the normal distribution trend,with photosensitive trait and its photosensitive index showing mid-parent heterosis.2.QTL mapping showed that,54 QTL related with six photosensitive related traits and their photosensitive index were identified by using complete interval mapping,including days to tasseling(12),photosensitive index of tasseling(7),days to pollen-shedding(4)and photosensitivity index of days to pollen-shedding(5);days to silking(6)and photosensitivity index of days to silking(4);plant height(3)and photosensitivity index of plant height(1);ear height(9)and photosensitivity index of ear height(0);the leaf number(2)and photosensitivity index of number leaves(1)QTL;with single QTL can explain 7.76%-39.57%of the phenotypic variation.3.GWAS analysis showed that,a total of 233 SNPs were detected to be related with photoperiod sensitivity related traits.Among them,21,32 and 48 QTNs controlling the variation of 6 photosensitive traits were detected in Guiyang,Sanya and Zhangye,respectively.67 and 65 QTNs controlling the variation of 6photosensitive traits were detected in Sanya/Zhangye and Guiyang/Zhangye,respectively.4.“The common”QTL/QTNs analysis showed that,for QT population under different light length conditions,a total of 14 common QTLs were identified,with 13common QTL to be related with maize flowering related traits(days totasseling,days topollen-shedding,days tosilking);One was related to ear height.These QTL all showed the phenomenon of"one multiple effects".At the same time,GWAS results showed that,a total of 36 SNPs were detected to be related with photosensitivity-related traits,and 18 SNPs were detected to be related with photosensitivity index.5.Candidate gene analysis showed that,a total of 20 candidate genes controlling photosensitive related traits were identified,including Zm00001d029448?Zm00001d007339?Zm00001d041380?Zm00001d016370?Zm00001d012761?Zm00001d043064?Zm00001d015974?Zm00001d042967?Zm00001d042968?Zm00001d042904?Zm00001d008914?Zm00001d008911?Zm00001d026511?Zm00001d040534?Zm00001d039049?Zm00001d018627?Zm00001d023420?Zm00001d038087.Wherein Zm00001d029448 showed one specific domain of CCT,showed participation in photoperiodic phenomena in plants.Zm00001d023420 gene encodes plant flowering FT gene,which controls the photoperiod flowering regulation process and induces plant early flowering,and is a typical flowering promoter.Zm00001d038087 encodes the dwarf gene(DWARF),which is a known key gene controlling plant height.The deletion of DWARF leads to significant plant dwarfing.These genes may impact maize's photoperiod sensitivity through gene's expression level,would be treated as main candidate genes for maize photoperiod sensitivity.