QTL mapping for plant biomass, nitrogen concentration and nitrogen accumulation in maize under high and low N conditions using SSSL

Objectives Plant biomass, nitrogen concentration and nitrogen accumulation of maize are closely related to grain yield and quality. In this study, we have mapped QTLs of these traits at maturity stage under high and low nitrogen levels by using single segment substitution lines (SSSL). The purpose of this study is to lay a foundation for fine mapping of genes that related to nitrogen efficiency and cloning of major QTLs.

Methods The SSSL constructed by Xu178 and Zong 3, which had significant difference in nitrogen efficiency, were used for pot culture. High nitrogen (HN, 0.15 g/kg) and low nitrogen (LN, 0.05 g/kg) were setup for all the lines. The plant biomass, nitrogen concentration and nitrogen accumulation of the leaves and stalks of maize were analyzed at mature stage. The T-test method was used to analyze the phenotype differences between SSSL and recurrent parent Xu178, and the QTLs were mapped in the SSR genetic linkage map at P < 0.05.

Results 133 QTLs (additive effect contribution: from –40.75%～12.69%) were mapped under high and low nitrogen conditions. There were 49 QTLs related to plant biomass, among which 26 QTLs were detected under HN condition and 23 QTLs were detected under LN condition. And 24 QTLs for N concentration were detected, containing 17 QTLs for stalk N concentration (8 QTLs under HN condition and 9 QTLs under LN condition), and 7 QTLs for leaf N concentration were detected (5 QTLs under HN condition and 2 QTLs under LN condition). There were 60 QTLs for N accumulation, including 33 QTLs for stalk N accumulation (27 QTLs under HN and 6 QTLs under LN condition). There were 27 QTLs detected for leaf N accumulation (11 QTLs under HN and 16 QTLs under LN condition). These QTLs were distributed on 10 chromosomes of the maize, and the chromosome 4 was located the most (19), whereas the chromosome 5 located the least (only 6 QTLs).

Conclusions In this study, the HN-specific QTLs for shoot dry weight and N accumulation in leaf and stalk were mapped on segments of umc1077–umc2350 (bin 10.04), umc2350–bnlg1028 (bin 10.04). And the LN-specific QTLs for them were mapped on segments of umc2377–bnlg1647 (bin 3.01), end–phi072 (bin 4.00), bnlg1444–umc2041 (bin 4.08) and bnlg1863–bnlg2046 (bin 8.03). We recommend high possibility of these QTLs containing the key gene segments controlling the nitrogen efficiency of maize, and will continue to conduct fine location in the future.