Genetic improvement of maize for nitrogen use efficiency
1995
Smith, M.M. | Miles, C.A. | Beem, J. van
Synthetic nitrogen fertilizer is derived from a non-renewable source, of limited availability in many areas, and environmentally harmful in others. Using breeding to lower crop demand for nitrogen would ameliorate these problems. The few reported results of maize selection under high and low nitrogen availability show significant improvements in nitrogen efficiency and yield under stress. Significant interactions of commercial varieties with nitrogen availability levels also indicate potential to improve performance under low nitrogen levels. High environmental variation and genotype by environment interaction complicate selection in nutrient- stressed environments. A growth chamber screening method has been developed to evaluate nitrogen stress responses under uniform conditions. Component processes may be less affected by environmental variability and genotype by environment interaction than yield, and easier to measure. Genetic variation has been documented for pre-flowering nitrogen accumulation, protease activity, and nitrate reductase activity, all of which are important components of nitrogen utilization in maize. Whole plant traits correlated with yield under nitrogen stress also would facilitate breeding. Chlorophyll meter readings and stem volume (to estimate above-ground plant biomass) are promising options. Root characteristics contributing to nutrient use efficiency are largely unknown and unexploited, due to the destructive, time consuming, and expensive nature of root measurement methods. Electrical capacitance is proposed as a rapid, inexpensive, and non-destructive method to assess root system surface area. Future research will need to focus on interactions between nitrogen and water supply, and the nitrogen content of grain and stover from genetic materials with improved nitrogen use efficiency. To place these genotypes appropriately within cropping systems, we will need to understand the basis for their nitrogen use efficiency.
显示更多 [+] 显示较少 [-]