Program 4: Linkage of yield and grain nitrogen


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.

Relationship between grain yield (t/ha) and grain protein concentration (%) for 25 Australian varieties in 5 South Australian sites in 2015 (from Australian National Variety Trial)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.


The effect of different senescence pattern on internal N recycling is analysed by fluorescence imaging and metabolomics.

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 with selected cultivars and mapping populations. The effect of different senescence pattern on internal N recycling is analysed by fluorescence imaging and metabolomics. We will identify QTL for high GPC and N remobilization from field and glasshouse experimental data. A wheat diversity panel and derived nested association mapping (NAM) populations will be examined for GPC and related traits to explore genetic potential and to deliver QTL and molecular markers to breeding programs.

Subprogram 4.2. Identify anatomical and molecular components affecting grain N loading

Defining transport processes regulating seed N delivery in wheat
What are the differences in grain anatomy and physiology between high and low GPC
wheat genotypes? Within this program, we will dissect the components relevant for
grain N loading – metabolites, N transporters and assimilatory genes will be examined
in developing grains and flag leaves in varieties contrasting for GPC. Identified key traits,
signature metabolites and genes will be explored for developing wheat that is
maximising grain N content at high yield.



Mamoru Okamoto (program 4 leader, Uni of Adelaide)
Margaret Kirika (PhD student, Uni of Adelaide)
Larissa Chirkova (technical support, Uni of Adelaide)
Paul Eckermann (statistics support, Uni of Adelaide)
Sanjiv Satija (technical support, Uni of Adelaide)
Brent Kaiser (subprogram 4.2 leader, Uni of Sydney)
Julie Dechorgnat (researcher, subprogram 4.2, Uni of Sydney)
Sigrid Heuer (CI, Rothamsted Research)