QTL Analysis Of Seedling Traits Under Different Nitrogen Forms And Haplotype Analysis Of Glutamine Synthetase In Wheat

Wheat is one of the most important grain crops in China with great demand. It plays animportant role to use nitrogen fertilizer for improving wheat yield. At present, our countryfacing a serious of fertilizer resources crisis that low nitrogen use efficiency。Therefore,application and foundation studies on wheat nitrogen use efficiency are so vital nowadays.The nutrient-related traits of N metabolism and are complicated quantitative traits.Quantitative trait locus (QTL) analysis provides an effective approach to dissect complicatedtraits into component loci and study their relative effects on a specific trait. In this study, eightmorphological traits at the seedling stage were investigated using a set of recombinant inbredlines (RILs) derived from ‘Chuan35050’בShannong483’. The objective of this study wasto detect QTLs at the seedling stage grown under different nitrogen forms.Glutaminesynthetase plays fundamental roles in plant N assimilation and is regarded as the ‘hinge’ overwhich inorganic N is converted into its organic form. GS isoenzymes have demonstratedcentral effects to the enhancement of plant N use efficiency. The characterization of GS genesand the haplotype of GS are very important for marker-assisted selection (MAS) in wheatbreeding.(1) Plant growth under different nitrogen forms. In this study, eight morphological traitsat the seedling stage were investigated using a set of recombinant inbred lines (RILs). Threehydroponic culture experiments were conducted using three different NO3-/NH4+ratios (T1at50/50%, T2at100/0%and T3at0/100%). The investigated traits in T2and T1weresignificantly higher than T3in all three experiments, indicating that NO3-promoted or NH4+suppressed the production of biomass. Comparing T1with T2, NO3-significantly increasedthe values of root fresh weight (RFW), total fresh weight (TFW) and root dry weight (RDW)and significantly decreased shoot dry weight (SDW).(2) QTL mapping for seedling traits under different nitrogen forms in wheat. A total of 147quantitative trait loci (QTLs) for the eight traits were detected on18chromosomes(except2A,3D and4D). A single QTL in different environments explained6.1–55.6%of thephenotypic variations. Among them,16QTLs (QRfw-1A, QRfw-1D, QSfw-1D, QSfw-2B.1,QTfw-1A, QTfw-1D, QRsfw-2B, QRsfw-3B.1, QRdw-1A.1, QRdw-1A.2, QSdw-6B.1,QSdw-7A.1, QTdw-1A.1, QRsdw-1A.1, QRsdw-5A.1and QRsdw-7A.1) were detected in morethan three of the nine treatment-experiments, and most of the16QTLs made largecontributions of approximately15%. Surprisingly, QRsfw-4A.1and QRsfw-4A.2explained asmuch as47.9and55.5%of the phenotypic variation, respectively. Thirteen important QTLclusters (C1-C13) with more than four QTLs and involving66QTLs (44.9%) were mappedon chromosomes1A,1D,2B,2D,4A,4B,5B,5D,6B,7A and7B.(3) Haplotype analysis of glutamine synthetase (GSe1/GSr1). In the present study, thefull-length genomic DNA (gDNA) sequence of GSe1/GSr1was obtained from30wheatvarieties and three dipolidy wheat. GSr1comprises2484bp and has eight exons and sevenintrons. Three single nucleotide polymorphisms (SNPs) were detected in introns, resultingtwo haplotypes: Hap1and Hap2.The complete length for coding region is different in A, Band D genome. GSe1-A has ten exons and nine introns. Thirteen single nucleotidepolymorphisms (SNPs) and eight insertions and deletions of DNA segments (InDels) weredetected in introns, resulting two haplotypes; GSe1-B has only one haplotype; GSe1-Dcomprises2829bp and has twelve exons and eleven introns. Two single nucleotidepolymorphisms (SNPs) were detected, resulting two haplotypes.