QTL Mapping For Root And Grain Yield Traits In Maize Under Two Nitrogen Conditions

Increasing in population and food requirement and environmental pollution has caused great concern in the 21st century. Development of nitrogen (N) efficient cultivars is one of the ways to resolve such problems. Root architecture is an important factor for efficient N acquisition and closely related to grain yield. The objective of this study is to reveal the genetic basis for root and grain yield traits under different N levels so as to develop the marker assisted selection (MAS) techniques for N-efficiency breeding in maize. A recombinant inbred lines (RIL) population derived from 478×Wu312 was used to identify the quantitative trait loci (QTL) for root and grain yield traits under different N levels. QTL detection was performed by composite interval mapping using the software Windows QTL Cartographer version 2.5 with that LOD>2.5 as the criteria. The main results were as followed:1.Totally 53 QTLs were identified related to root traits in hydroponics at the seedling stage (shoot dry weight, root dry weight, max root length, root dry weight / shoot dry weight, ) and field grain yield traits(Grain yield, 100 kernel weight, Grain number per ear, Kernel rows) at high and low N levels. These QTLs were located on nine chromosomes (1, 2, 3, 4, 5, 6, 7, 8,9,10). The pleiotropism is very common in these loci which unevenly distributed on chromosomes. Many loci were clustered on Chromosomes1,3,4,5,6,8 and 9, suggesting these segments may have potential value for improvement of root and yield traits.2. Conform loci for maize root and grain yield traits were constructed based on the results of this study and other published QTL data. Twelve QTLs relevant to maize root and grain yield traits were found which may be useful in MAS and/or genetic analysis of root and grain yield traits in maize.3. A QTL flanked between bnlg1174-nc012 on chromosome 6 was found to be a major QTL for root dry weight which could explain 25.3% of phenotypic variation. In the same chromosome section, 8 QTLs for root and grain yield traits previously published were found closely linked to this QTL. It is suggested that this chromosome region can be a candidate for fine mapping of QTLs related to root and grain yield traits.