Abstract
Grain protein content (GPC), is one of the most important trait in wheat and its characterized by a very complex genetic control. The identification of wheat varieties with high GPC (HGPC), as well as the characterization of central enzymes involved in these processes, are important for more sustainable agricultural practices. In this study, we focused on Glutamine synthetase (GS) as a candidate to study GPC in wheat. We analyzed GS expression and its enzymatic activity in different tissues and phenological stages in 10 durum wheat genotypes with different GPC. Although each genotype performed quite differently from the others, both because their genetic variability and their adaptability to specific environmental conditions, the highest GS activity and expression were found in genotypes with HGPC and vice versa the lowest ones in genotypes with low GPC (LGPC). Moreover, in genotypes contrasting in GPC bred at different nitrogen regimes (0, 60, 140 N Unit/ha) GS behaved differently in diverse organs. Nitrogen supplement increased GS expression and activity in roots of all genotypes, highlighting the key role of this enzyme in nitrogen assimilation and ammonium detoxification in roots. Otherwise, nitrogen treatments decreased GS expression and activity in the leaves of HGPC genotypes and did not affect GS in the leaves of LGPC genotypes. Finally, no changes in GS and soluble protein content occurred at the filling stage in the caryopses of all analyzed genotypes.
Highlights
Global agriculture urgently requires a modification of standard breeding practices and management policies
The average Grain protein content (GPC) values of the two groups were significantly different (Figure 1). Both enzyme activity and gene expression of Glutamine synthetase (GS), a candidate gene for nitrogen use efficiency (NUE) and GPC, were analyzed in roots and leaves at different phenological stages in the 10 selected wheat genotypes grown in the field during the 2014 season
The highest GS activities were found in two high GPC (HGPC) genotypes (Cannizzo and Svevo) and the lowest ones in the low GPC (LGPC) genotypes Vesuvio and Canyon (Figure 2A)
Summary
Global agriculture urgently requires a modification of standard breeding practices and management policies. As reported in the statistics from the Food and Agricultural Organization of the United Nations, the yield of crops, especially wheat, soybean and maize, have slowed to a growth rate of about 1% annually, and in some specific cases, as in developed countries, the growth rate is quite close to zero (Fischer et al, 2009). Much of this nitrogen is wasted, as well – of the total amount of N supplied, only 30–50% is taken up by the plant (depending on the species and cultivar) and used in different biochemical pathways. Several studies and international projects have since highlighted the importance of defining the optimum timing and rate of nitrogen application during plant growth to maximize yield
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