Fine Mapping And Map-based Cloning Of QTL Controlling Plant Height And Spike Length On Chromosome 2D In Common Wheat(Triticum Aestivum L.)

Plant height?PHT?is a crucial trait related to plant architecture and yield potential.Therefore,the identification of quantitative trait loci?QTL?controlling PHT and dissection of the underlying genetic basis of PHT would help improve the efficiency of designed breeding in wheat.In the present study,two QTL linked in coupling phase on the short ann of chromosome 2D with pleiotropic effects on PHT and spike length?SL?,QPht/Sl.cau-2D.1 and QPht/Sl.cau-2D.2,were separated and characterized.Furthermore,QPht/Sl.cau-2D.2 was finely mapped and one candidate gene was identified.The main results obtained are as follows:1.To enrich the genetic region of QPht/Sl.cau-2D.1 and QPht/Sl.cau-2D.2,a total of 17 chromosome 2D specific SSR markers were developed by using the reference sequence of Chinese Spring and Aegilops tauschii.Furthermore,these two QTL were dissected and characterized using segregating populations and two set of NILs.QPht/Sl.cau-2D.1 was a novel QTL located between SNP makers BS00022234₅1 and BobWhite_rep_c63957₁472.QPht/Sl.cau-2D.2 was mapped between two SSR markers,SSR-2062 and Xgwm484,which was located on the same genomic interval as Rht8.In addition,the diagnostic marker tightly linked with each QTL was developed and used for the haplotype analysis.The results exibited that the frequency of the height-reduced allele of QPht/Sl.cau-2D.1 was much lower than that of QPht/Sl.cau-2D.2,suggesting that this novel QTL may be an attractive target for genetic improvement.At the cytological level,significant difference in cell length was observed between the NILs of QPht/Sl.cau-2D.2.By contrast,there was no difference in cell length between NILs of QPht/Sl.Lcau-2D.1,indicating that the underlying molecular mechanism for these two QTL may be different.2.To fine map the QPht/Sl.cau-2D.2,35 recombinants were selected from a segregating population with 3812 individuals derived from a heterozagous line?RIL171?.Finally,QPht/Sl.cau-2D.2 was mapped to a narrow genetic interval between markers INDEL-2005 and SSR-2433,which corresponded to a 94 Kb reference genomic region of Chinese Spring,including one candidate gene,designated as Rht2DS-a.When compared to the allele of Rht2DS-a in parent J411,the protein encoded by the allele in Y8679 was incomplete,which was caused by one SNP variation and one 1-bp deletion.Moreover,one functional marker for Rht2DS-a was developed.