Optimising nutrient use in cereals

Lead Research Organisation: Rothamsted Research
Department Name: Unlisted

Abstract

Nitrogen (N) is a major input determining productivity, with considerable financial and environmental costs. N is required for canopy formation for efficient carbon capture, thus determining yield. N use efficiency (NUE) (yield/available N) is the product of N uptake efficiency (N taken up/N available) and N utilization efficiency (yield/N taken up). Component traits will be de-convoluted and component genes identified, exploiting variation in alleles and expression profiles in modern wheat cultivars. Roles of nitrate transporters in the roots in controlling uptake processes will be determined: cellular nitrate pools will be measured and compared in soil grown roots of selected cultivars; nitrate influx will be measured on roots growing in soil; the wasteful loss of nitrate from root cells through the efflux pathways will be assessed; key nitrate transporters involved in sensing N availability and uptake will be characterised. Traits associated with NUtE (N and carbon assimilation and partitioning) will be de-convoluted, mapped and data made available for modelling studies. N is utilised for canopy production/photosynthesis which subsequently determines yield and this same N is utilised for grain formation, obviating the need for further uptake. Timing of senescence is critical to extend the photosynthetically active period and to maximise N transfer to the grain. We will investigate variation in associated parameters (canopy architecture, photosynthetic capacity, N storage and remobilisation) screening germplasm, functional staygreen mutants and transgenic lines. Key genes, both those involved in the pathways themselves or in the control of the pathways (transcription factors, signalling pathways) which underpin NUE traits will be identified using mapping approaches and transcriptomics. Cell-specific gene expression of glutamine synthetase and other candidate genes will be examined.

Publications

10 25 50

 
Description 1. The key output was the dissection of the complex trait of nitrogen use efficiency into component processes and the determination of existing variation in these processes and overall agronomic performance across a range of elite germplasm and mapping populations at a range of nitrogen inputs. The independence of NUpE and NUtE traits was confirmed and variation in the component traits was significant. Variation in the year to year stability was apparent. Other studies identified two mutant lines (durum wheat) with large flag leaves and high chlorophyll content (by SPAD estimation), flag leaf senescence in both lines was delayed and the grain yield per spike was high. Trait analysis information on a variety of germplasm resources, including those in WGIN, was used to drive more detailed analysis of NUE traits in wheat and used to dissect the involvement of contributing genes.

2. In addition, new QTLs for N use efficiency were identified as a first step in the forward genetics pipeline for fine mapping and new gene discovery in bread wheat. In parallel architecture and functional properties of roots were analysed. Three wheat cultivars were selected for detailed study on the basis of their differing N uptake efficiencies: their root architecture compared and significant differences in the pattern of lateral root development between the cultivars were found. Comparison of root physiological parameters of the cultivars and their ability to influence the nitrate concentration at the root surface in soil rhizotrons also showed major differences; this was then used to assess which root parameters are important for N uptake efficiency. Both the elite lines and the Avalon x Cadenza population showed differential proliferation related to N uptake ability and differential responses to N-availability. Root architectural QTLs were being compared with observed field NUE performance traits

3. Additional research arising from this project included wider germplasm screening (landraces, wild relatives and additional mapping populations) and validation in transgenic lines of key gene function, particularly for overall pathway/trait control via signalling pathways and transcription factors, with the potential for delivery of improved transgenic lines/markers for breeding.

4. Specific trait information obtained on the role of cytosolic nitrate in signalling nitrogen status of plant cells was established (which may be used as a physiological marker for nitrogen-use efficiency of crop varieties).

5. Genes controlling nutrient uptake, canopy longevity/photosynthetic capacity and controls of nitrogen remobilisation were identified and placed into pipelines for validation and delivery to pre-breeding, with a particular focus on families of membrane transporters, assimilatory enzymes, genes relating to senescence and specifically alanine amino transferase.

6. Transgenic lines with manipulated traits were generated and are now available for further study. Alanine amino transferase over-expression lines failed to show significant expression above endogenous levels and further work on this trait was halted.

7. This work delivers to long term goals of varieties with optimised yields at current or reduced nitrogen input levels, for wheats with specified end uses (starch/protein optimisation).
Exploitation Route Formed basis of subsequent ISP (20:20 wheat, wheat pre-breeding LOLA and components of WGIN projects.
Adopted by policy agencies with regard to fertiliser use.
Adopted by plant breeders by targeting specific traits.
Adopted by farmers to optimised agronomy related to NUE.
Sectors Agriculture, Food and Drink,Environment

 
Description Presentation at Significance of Sulfur in High-Input Cropping Systems Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation 'Linking genes to field performance: adventures in sulfur research'
Year(s) Of Engagement Activity 2017