Abstract: 【Objective】The breeding program in crop root plays an important role in determining yield potential and broad adaptation. Jing 411 as one of the most important elite parents has been widely used in the Northern Winter Wheat Region. Understanding the principal components and detecting the root traits loci in Jing 411 will provide important information for future genetic improvement by high density SNP markers.【Method】The core parent Jing 411 and its 14 derivative varieties and lines including six derivative and eight varieties in the first and second generations were used in present study. The uniform grains of each variety were selected for germinating in seedling plate for 6 days, and then six healthy and consistent plants were selected to culture 15 days in cultivating plates. Every variety with three replicates in each cultivating plate was planted in nutrient solution. Nine root parameters including maximum length root, length of branch root, length of main root, total length of roots, surface area of branch roots, surface area of main root, surface area of total roots, number of total root tips, and root dry weight were measured after 15 days of culture. The genetic structure and components of Jing 411 and its derivative populations of different generations were compared. The whole-genome association mapping was employed to identify the chromosome region controlling seedling root traits loci using 90K SNP markers. 【Result】The averaged genetic similarity index was 57.9% among Jing 411 and its derivatives, and the clustering results for these genotypes were generally in consistent with their pedigree. Jing 411 had the same allele ratios of 63.9% and 67.9% to its first and second generation derivatives, respectively. Most of Jing 411 derivatives were obtained from the second generation by backcrossing with the elite parent or its derivatives, and the contribution of Jing 411 was higher than theoretical expectation. On A, B and D genomes, the same allele ratios from the elite parent were 62.2%, 61.3% and 74.3%, respectively. Jing 411 exhibited more branch root and total root tips than its derivatives, however, the maximum length root and root dry weight has been improved significantly in the derivatives. Thirty-five loci showed significant association with root traits using stepwise model selection with Proc GLMselect in SAS software. Two new loci for root traits on the long arm of chromosomes 3D and 5B were linked with the SNP markers wsnp_Ex_c1032_1972861 and BS00100708_51, respectively. The gene and its linked SNP marker could be used for selecting root traits in the derivatives of Jing 411. Alleles were positively related with root traits from Jing 411 at 26 loci, and Zhongmai 175 and CA0958 remained more positive root loci delivered from the core parents, accounted for 73.1%. 【Conclusion】Conventional breeding program could effectively collect available genetic components, and promoted the root characters through selected outstanding above-agronomic parameters. A notable example in the improvement of Jing 411 was the variety Zhongmai 175, which carried more loci from the elite parent than other derivatives, and had superior root traits, agronomic traits and wide adaptation than its parent Jing 411.

Key words: common wheat , elite parent , root traits , SNP marker , new locus