Development Of A Set Of Chromosome Segment Substitution Lines Of Maize And Mapping QTL For Yield Related Traits

Unveiling the genetic basis of grain yield and yield-related traits is useful for guiding the genetic improvement of crop plants. Due to the simple genetic background, Chromosome Segment Substitution Lines decomposed complex quantitative trait into a single Mondor factor, is a deal population for QTL fine mapping and gene cloning. In this study, we constructed a set of130chromosome segment substitution lines (CSSLs) using Nongxi531as the donor and H21as recipient by continuous backcrossing and selfing. Using molecular markers assist selection (MAS), we analyzed the genetic construction and background of CSSLs in per backcrossing generation, and further developed a CSSLs population with high percentage of recurrent parent. As well as, quantitative trait locus (QTL) for yield related traits in maize were identified based on the phenotype from three environments. The results were mainly listed as following.1. The genotypes of a set of CSSLs were analyzed using176SSR markers. Total of1277donor segments were introgressed into H21genome in the set of CSSLs with about10segments per line. The accumulative size of introgressed donor segments was-90486.0cM on the basis of reference map IBM2008neighbors. The size of unique introgressed segments was～6130.0cM, which covered85.8%genome of H21.2. The genetic structure of populations was evaluated by analyzing percentage of the recurrent genome coverage (PRC), percentage of the recurrent genome (PRG), donor segment number and size of every generation. In BC6F1, the size of unique introgressed segments covered77.63%genome of H21, the average PRG of CSSLs was97.48%. The donor segment number ranged from1to30, with an average of6. The segment size ranged from19.35cM to1692.19cM, with an average of333.60cM. In BC7F1, the size of unique introgressed segments covered75.95%genome of H21, the average PRG of CSSLs was98.67%. The donor segment number ranged from1to22, with an average of4. The segment size ranged from9.93cM to975.03cM, with an average of174.98cM.3. We constructed a CSSLs population with104families using130CSSLs (BC4F4) by backcrossing with H21for three generations. Total of89CSSLs were harboring with single donor segment, all of introgressed segments covered48.86%genome of H21, while the donor segments from the remaining11CSSLs covered27.09%genome of H21. These11CSSLs still need to be backcrossed because of lower percentage of recurrent parent.4. A total of11QTLs for KRN,4QTLs for ear length and7QTLs for kernel number per row were identified across multiple environments with8.47%-19.44%phenotypic variation explained by single QTL. Of which,6major QTLs with large genetic effects were identified across multiple environments. We found that interactions between QTLs were broadly existed by comparing the phenotype of adverse CSSLs which were harboring different donor segments, indicating that epistasis might be an important genetic component of yield trait in maize.5. We identified4QTL-rich regions and11consensus QTLs which might control the formation and development of yield and yield related traits. Those CSSLs harboring favorable alleles showed more KRN than H21, could be employed as improved lines of H21in maize breeding program.