Abstract
Crop production on soils containing sub-optimal levels of nitrogen (N) severely compromises yield potential. The development of plant varieties displaying high N use efficiency (NUE) will optimize N fertilizer use and reduce the environmental damage caused by excess N application. Maize is one of the most important crops cultivated worldwide. Identification of the genotypes with an enhanced NUE in the field is both time and resource consuming and sometime is difficult due to the regulation in the biotechnology programs. Identification of traits associated with adaptation to N limitation at an early vegetative stage which could reflect NUE at maturity is in need. We developed a hydroponic growth system and used it to test two genotypes that were different in their NUE at maturity under N limitation. One genotype SRG-200 showed a higher NUE than the other genotype SRG-100 and we used its hybrid SRG-150 as a reference for NUE. A number of phenotypic, molecular, and metabolic factors were tested using these three genetic lines at an early vegetative stage to determine which of these could be more indicative of predicting improved NUE at an early seedling stage. These include a transcriptional analysis which showed that the higher NUE in SRG-200 genotype is associated with higher transcript levels for the genes involved in nitrate transport, N assimilation, and GS and that the SRG-200 genotype maintained higher sugar content in leaves. Those identified in this study could be useful indicators for selecting promising maize lines at early stages to help develop elite varieties showing an enhanced NUE.
Highlights
Nitrogen (N) is an essential element required for many physiological processes during the plant life cycle
Improving plant nitrogen use efficiency (NUE) and increasing their adaptation under lower nitrogen levels will improve the agronomic value of fertilizers, save energy required for fertilizer production, and minimize damage to the environment
The parent line SRG-100 had a lower NUE compared to the other parent line SRG-200 which was similar to the hybrid SRG-150
Summary
Nitrogen (N) is an essential element required for many physiological processes during the plant life cycle. Improving plant nitrogen use efficiency (NUE) and increasing their adaptation under lower nitrogen levels will improve the agronomic value of fertilizers, save energy required for fertilizer production, and minimize damage to the environment. The root system plays an important role in nutrient uptake from the soil, especially at the early seedling stage. Plants are dependent on their own roots to uptake the nutrient from the soil, and affecting the root system at this stage affects the rest of plant development. It has been suggested that the vigor of wheat seedling having stronger root growth help the plants to uptake the nitrogen quickly from the soil (Liao et al, 2004). Nitrogen translocation from the root to the shoots still requires elucidation especially at the early seedling stage where the N is a limiting factor to produce healthy and productive plants
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