Nitrogen (N) is an essential macro nutrient for plants and N fertilizers have to be applied in agricultural production systems to obtain high grain yield and prevent N depletion and soil degradation. Applied in excess, N can leach from the field which leads to pollution and eutrophication of water ways. Developing crops with enhanced N uptake and more efficient internal N use is therefore a global breeding goal.
In wheat, the grain protein content is an important quality trait determining processing quality and the price on the world market. In general, high yielding wheat varieties tend to have lower grain protein concentration (GPC). Although GPC can to some extent be managed by timely N fertilizer application, there are other factors determining the negative linkage between grain yield and grain protein.
Within this Hub program 4, we will address these issues through genetic, molecular and physiological approaches with the aim to identify genotypes, traits, and ultimately genes and markers that assist breeders in selecting wheat breeding lines with optimized internal use of N that maintain high GPC at high yield.
Subprogram 4.1. Identify key traits responsible for N remobilization and high grain N
To achieve high GPC, plants need to remobilize N into grains more efficiently. We dissect the physiological steps of N movement within the plants of high or low GPC varieties. Total N and free amino acids in different tissues of the plant were analysed to identify key traits which control GPC. We particularly focus on traits such as N uptake from root and shoot, N responsiveness, and N distribution within the whole plant. We also identified QTL for high GPC using mapping populations and a diversified wheat panel to deliver QTL and molecular markers to breeding programs.
Subprogram 4.2. Identify anatomical and molecular components affecting grain N loading
What are the differences in grain anatomy and physiology between high and low GPC
wheat genotypes? Within this subprogram, we dissected the components relevant for grain N loading – metabolites (amino acids, sugars) and genes were examined in developing grains and flag leaves in varieties contrasting for GPC.