| Brassica rapa, including a variety of vegetables and oilseed crops, is one of the most important species with Chinese characteristic and significant effect in China. Its germplasm is abundance in China and the leaf morphology have wide varition among different subspecies. Recently, the leaf with different morphology has become the new breeding dircetion. In Arabidopsis, many genes related to leaf morphology have been identified, but only few genes have been found in B. rapa. With the completion of B, rapa genome sequencing project, the understanding of leaf morphology and QTL for morphological candidate genes in B. rapa become possible.In this study, based on the B. rapa genome sequencing project, comparative genomics was used for the identified orthologs which related to leaf curvature, size, lobe and index in B. rapa. Three parents with different leaf morphology were selected, two permanent populations and their genetic maps were constructed. QTL for leaf morphology traits were conducted. Combined with transcriptome data of natural population and whole genome sequence of B. rapa, QTL were further analysised. The conclusions of this dissertation as follows:1. In order to elucidate leaf curvature, leaf size, leaf lobe, leaf index and gibbrerllin genes in B. rapa, comparative genomic analyses were used between A. thaliana and B. rapa on genome-wide level. In B. rapa,75,69,23and17genes which regulated in leaf curveture, leaf size, leaf lobe and leaf index were found. Except Bra040948and Bra040469, all the genes were anchored on ten chromosomes in B. rapa. Fifty-seven putative GA pathway genes was successfully anchored on10chromosomes and a high co-linearity GA pathways between A. thaliana and B. rapa was established. The homologous of GA pathway genes between B. rapa and A. thaliana share37.7%-92.2%nucleotide sequence identity. In B. rapa,96%of the GA pathway genes and83%leaf morphological genes exhibit synteny with A. thaliana. The results correspond with the evolutionary divergence of B. rapa.2. An genetic map of993.6cM with10linkage groups were constructed in the Z16_SZQ F1DH population. For the Z16_L144BC2DH pupulation, another genetic map of563.3cM were also constructed. Markers were developed based on the resequencing data of their parents. According to the genome sequence of B. rapa, the genetic map of Z16_L143BC2DH population which was constructed on the former study and genetic map of Z16_L144BC2DH population were used for the construction of integrated map. The integrated map contained238InDel markers including67markers which located in the exons or introns in annotated genes. They are the coseparated markers with annotated genes.3. Leaf morphological traits were measured in three populations in different seasons. Analyses of interdependency indicated that the leaf length, leaf width, petiole length and petiole width have significant correlation. In Z16_SZQ FiDH, Z16_L143BC2DH and Z16_L144BC2DH populations,39,25,18QTLs which related to leaf morphology were detected, respectively.4. Genome sequence was used for the analyses of stable QTL. In linkage group A03and A10, stable QTL of leaf lobe were detected and BrGA20ox3was regarded as the candidate gene. Exogenous GA3could inhibit lobed phenotype in L143. Leaf index was detected in BrID111431on A03, BrXTH9which was the ortholog of BcXTH1and54Kb away from BrID111431was regarded as the candidate gene. Transcriptome data of natural population also indicated that there was significant correlation between leaf index and expression of BrXTH9. QTL of three leaf curvatures were detected in one common region of54Kb physical distance between BrID10669-BrID11869. In B. rapa,42annotated genes existed in this regions, but candidate gene need to be further studied. The QTL of petiole width and ratio of petiole width to leaf width located in the locus of BrIDFIS4which was cosegerated with BrFIE. In A. thaliana, mutation of BrFIE could lead to narrow petiole, small leaf, so it could be the candidate gene for these traits.
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