Primary Mapping Of Flowering Time QTL QFT2.1 At The Top Of Chr.2 In Brassica Rapa

Chromosome segment substitution lines?CSSLs?are useful tools for precise mapping of quantitative trait loci?QTLs?and evaluation of gene actions or interactions in theoretical studies.The decrease of yield and quality for Chinese cabbage caused by premature bolting is one of the problems that need to be solved urgently.The utilization of late bolting genes in wild resources for breeding late bolting varieties is the most feasible ways for solving the problem.The further fine mapping and cloning of late bolting genes is of great importance for clarifying the late bolting mechanism and breeding late bolting varities.In this study,six CSSLs related to bolting were verified for both phenotype and gentotype,and a CSSL-F₂segregating population derived from the selected CSSL and recurrent parent was constructed.The results as follows:1.Based on previous studies in F₂,RIL,and CSSL,six CSSLs were selected for further identification.In the selected six CSSLs,RcBr as the recurrent parent?background?,most of the QTLs controlling bolting traits are located on chromosome?Chr.?A02.The QTLs associated with bolting were also detected on chromosomes A03,A06,A07,and A08,and QTLs associated with bolting were not detected on chromosomes A01,A04,A05,A09,and A10.Compared with the previous results,16SWD001 was selected as the location material.The genetic background of the CSSL was identical to that of the recurrent parent RcBr.Between the marker BrFLC₂ and the marker Nia-m105a at the top of the cabbage A02 linkage group,a QTL related to the bolting trait was detected and named qFT2.1.2.CSSL-F₂ segregating population was constructed derived from the crosses between CSSL-qFT2.1 and RcBr.Using two polymorphic flanking markers W-30 and W-42,and 68recombinants of CSSL-F₂ were selected from total 1687 segregating population,using two flanking markers W-30 and W-42 and their nearby six pairs of polymorphic primers were screened for genotype and combined with phenotypic data analysis results.We narrowed the candidate region to a physical distance of 494.6 kb,between markers W-36 and W-42.3.A flowering-related gene was detected in qFT2.1 494.6 kb:Bra023541,which is functionally similar to the gene AT5G15850 in Arabidopsis thaliana.The gene AT5G15850 in Arabidopsis are similar in function.Furthermore,AT5G04110 gene plays an important role in circadian rhythm,flower development regulation,transcriptional regulation,DNA templating,response to light stimulation,transcription and DNA templatization in Arabidopsis thaliana.In the germination stage of mature plants,petal differentiation and expansion,plant embryos bilateral phase,plant embryo cotyledon stage,plant embryo sphere,and senescence period of the vascular leaf were all expressed.Thus,we predicted that Bra023541 gene is a major gene associated with flowering time on qFT2.1.The next step is functional verification.