Towards a Better Understanding of the Genetic and Physiological Basis for Nitrogen Use Efficiency in Maize

Abstract

To enhance our understanding of the genetic basis of nitrogen use efficiency in maize (Zea mays), we have developed a quantitative genetic approach by associating metabolic functions and agronomic traits to DNA markers. In this study, leaves of vegetative recombinant inbred lines of maize, already assessed for their agronomic performance, were analyzed for physiological traits such as nitrate content, nitrate reductase (NR), and glutamine synthetase (GS) activities. A significant genotypic variation was found for these traits and a positive correlation was observed between nitrate content, GS activity and yield, and its components. NR activity, on the other hand, was negatively correlated. These results suggest that increased productivity in maize genotypes was due to their ability to accumulate nitrate in their leaves during vegetative growth and to efficiently remobilize this stored nitrogen during grain filling. Quantitative trait loci (QTL) for various agronomic and physiological traits were searched for and located on the genetic map of maize. Coincidences of QTL for yield and its components with genes encoding cytosolic GS and the corresponding enzyme activity were detected. In particular, it appears that the GS locus on chromosome 5 is a good candidate gene that can, at least partially, explain variations in yield or kernel weight. Because at this locus coincidences of QTLs for grain yield, GS, NR activity, and nitrate content were also observed, we hypothesize that leaf nitrate accumulation and the reactions catalyzed by NR and GS are coregulated and represent key elements controlling nitrogen use efficiency in maize.

Estudo da eficiência de uso do nitrogênio em variedades locais e melhoradas de milho

“…A variabilidade genética para a atividade da glutamina sintetase (GS) bem como a sua correlação com a EUN têm sido demonstradas em vários estudos (Denbinski et al 1991, Lam et al 1995, Reggiani et al 1999, Hirel et al 2001. Denbinski et al (1991) verificaram que a seleção para alto teor protéico em milho foi acompanhada pelo incremento da atividade da GS no endosperma.…”

Inheritance of the efficiency of nitrogen uptake and utilization in winter wheat (Triticum aestivum L.) under diverse nutrition levels

“…the HATs system) are up-regulated by N shortage in the soil or feedback-regulation depending upon the shoots' demand for N (Wirén et al 1997;Forde 2002). Moreover, both processes-N uptake and N utilization-appear to be governed by different genetic factors (Hirel et al 2001;Gallais and Hirel 2004;Good et al 2004). For instance, results of extensive molecular studies on wheat and maize Gallais 2000, 2001;Quarrie et al 2005;Habash et al 2007;Laperche et al 2007) revealed that different sets of genes (QTL regions) controlled various components of the two major measures of N efficiency, and that expression of the genes (loci) was considerably dependent upon soil N status.…”

Genetic map construction and QTL analysis of nitrogen use efficiency in spinach (Spinacia oleracea L.)

“…NUE is a quantitative plant trait with a polygenic inheritance, which is influenced by N availability (Hirel et al 2001). The latter is difficult to control under field conditions (Fageria and Baligar 2005) and this will complicate genetic analysis of NUE variation.…”