Analysis of QTLs for Root Traits at Seedling Stage in Soybean

Very few quantitative trait loci (QTLs) for root traits have been identified in soybean [Glycine max (L.) Merr.], although root system plays important roles in the growth and development of a plant. The aim of this study was to localize QTLs for root traits at seedling stage in soybean. The mapping population contained 165 recombinant inbred lines (RILs), which was derived from the cross between Zhongdou 29 and Zhongdou 32. The seedlings were hydroponically cultured, and the root traits, including length of the main root, number of lateral roots, root weight, root volume, plant weight, shoot weight per plant, and ratio of root weight to shoot weight, were measured at V2 stage. Using composite interval mapping (CIM) method, 20 QTLs associated with roots and aerial part traits were mapped on 8 chromosomes, which included 9 major-effect QTLs on chromosomes 11 and 14 with the phenotypic contributions of 10.5-26.1%. On chromosomes 11 and 14, some QTLs for root traits and aerial part traits were distributed in clusters. This result is consistent with the correlation analysis of phenotypic traits, indicating that the root traits are associated with the shoot traits.