Evaluation of nitrogen efficiency for selected Shaan A and B maize inbred lines

This study was set up to explore the characteristics of nitrogen (N) use efficiency (NUE) of different groups (Shaan A group and Shann B group) of maize inbred lines, and to screen high N-efficient maize inbred lines. A total of 33 maize inbred lines from the Shaan B and Shaan A groups were used along with 4 elite inbred lines (‘zheng58’, ‘chang7-2’, ‘PH6WC’, ‘PH4CV’) as the control. The study analyzed SPAD value, green leaf area, dry matter accumulation as well as N uptake in stem, leaf and grain of maize inbred lines under no nitrogen N0, 0 kg(N)?hm^-2 and normal N N180, 180 kg(N)?hm^-2 levels. Based on principal component analysis (PCA), fuzzy membership function (FRF), stepwise regression analysis and the optimal regression equation, evaluation indexes for low N tolerance of maize inbred lines was established. The results indicated that SPAD value, green leaf area, stem dry weight and leaf dry weight at silking and grain N uptake were reliable secondary indicators for comprehensive evaluation of low N resistant ability of maize inbred lines. Using yield as primary index, among 37 maize inbred lines, 15 lines were determined as high yield with high N efficiency, 5 lines as low yields with high N efficiency, 15 lines as low yields with low N efficiency and 2 lines as high yields with low N efficiency. According to the integrated value of low N resistance (D) calculated using the secondary indexes, 37 maize inbred lines were also divided into three types — 15 lines of strongest resistance to low N with D ≥ 0.5, 15 lines of stronger resistance to low N with 0.35 ≤ D < 0.5, and 7 lines of poor resistant to low N with D < 0.35. Comprehensive analysis of two N levels showed that ‘KB215’, ‘KB417’, ‘KA225’, ‘KB081’ and ‘L123098-2’ had higher green area and stem and leaf dry matter at silking stage, greater grain N content and higher yield, and the strongest resistance to low N. Thus strengthening selection process of breeding environment and low N use effectively improved the utilization efficiency of N fertilizer of maize germplasm.