Objective 8 - Malcolm Hawkesford (RRes)
Improvements of nitrogen use efficiency(RRes) and quality QTLs linked to NUE(RRes)
Background
High cereal yields are currently dependant on large inputs of fertiliser nitrogen. Fertiliser production is expensive, requires energy from fossil fuels and excessive application has negative environmental consequences. However, high yields are an absolute requirement with current worldwide demands for grain. Developing wheat lines which give high yields with minimum N inputs is therefore a priority.In the next phase of WGIN we propose to target a major influence contributing to NUE, specifically canopy longevity/rate of canopy N remobilisation and also additionally perform trial studies to assess variation in early (seedling) N uptake as a contributor to seedling establishment and overall NUpE (uptake).
Consistency of performance (yield and quality) under varying nitrogen input levels and climatic conditions are a major target for breeders and is expected to increase in importance under changing climatic conditions. Such consistency is a major reason why the cultivar Hereward is still grown and regarded as a “gold standard” for breadmaking wheats, despite being first released in 1992 and outclassed in yield. The recent defra LINK programme RD-2004-2492 “Investigating wheat functionality through breeding and end use (FQS 23)” provides an opportunity to identify the genetic basis for this stability. Specifically, QTLs for bread-making quality independent of protein content were identified. Validation of such QTLs followed by identification of close markers and/or genes underlying them, open up the opportunity for more effective N use.
Activities
1. Dissect components of yield and NUE parameters in varieties of interest as identified in the preliminary screening in WGIN 1.2. Examine physiology/biochemical processes contributing to NUE and quantify expression of key genes in selected varieties.
3. Examine variation in NUE in more ‘exotic’ germplasm arising from WGIN.
4. Use mapping populations to identify robust key QTLs for NUE.
5. Examine variation in early seedling nitrogen uptake ability.
6. Determine whether functionality can be maintained at reduced grain protein. This will utilise bread making quality QTLs which are independent of protein content (and known storage proteins) as identified in a previous LINK project and derived from the Hereward x Malacca population.
Workplan
We plan to extend and refine the analysis of genotype x environment interactions with regard to NUE. Further field trials (all years) will utilise a common subset of varieties chosen from WGIN 1, supplemented with other ‘exotic’ germplasm arising from the WGIN studies, including a number of elite bread wheats, lines from the AE Watkins Collection, selected EMS mutation lines (stay-greens) and individual mapping population lines. Analysis in WGIN 1 was restricted to yield/N determination. However in the next research period, detailed molecular physiological measurements will help focus the key traits relating to NUE. These measurements are proposed to include canopy photosynthetic capacity, longevity and N-remobilisation rates as well as determination of levels of expression of the key genes involved in these process and genes proposed to have a control influence. Where possible, canopy contributions will be broken down into its components of individual leaves, stem, sheaf etc. Varieties will be screen at 4 N levels (0, 100, 200 and 350 kg/ha to ensure continuity with WGIN 1 and to provide a wide range of responses beyond the UK norm.
As a means of identifying key traits and dissecting relevant processes, WGIN 1 demonstrated the usefulness of mapping populations, principally the Avalon x Cadenza doubled haploid population. Initial trials indicated that whilst Cadenza parent lines out-performed Avalon in relation to NUE, the doubled haploid progeny lines demonstrated substantial transgressive segregation for all characteristics analysed. An example, measured nitrogen utilisation efficiency (in a single trial in 2007), is shown in the figure.
Further trials are required with this population at both low and high N inputs to validate and map the preliminary identified QTLs determined within WGIN 1. Furthermore a more detailed N response trial with a selected subset of lines encompassing an extensive analysis of plant component parts in terms of yield/N management/specific gene expression is required.
N-uptake is an essential component of overall NUE. Whilst overall N-uptake can be measured and NUpE estimated based on field soil data, it is difficult to breakdown the trait in field based experiments. Therefore we will investigate the variation in ability of seedlings (prior to GS30, to be confirmed experimentally) to take up N in a glass house-based experiments, in which fine control of both N-supply and seedling establishment can be achieved.
To ensure development of higher yielding wheats having the required properties for use in food processing, genes controlling grain functionality independently of protein content will be studied. This will be assessed by development of NILs (5 QTLs x 4NILs/QTL = 20 lines), using marker-assisted backcrossing of those bread making quality QTLs which are independent of protein content and known storage proteins. Replicated (x3) field trials will then be carried out for two years at 5N levels that span the current range used for growing wheats (100, 150, 200, 250, 300kg/Ha) followed by functionality analysis of selected samples (lab scale predictive tests, SE-HPLC and spiral white bread-making). Transcriptome profiling will be carried out on developing grain of selected NIL x N level combinations to identify transcripts and hence candidate genes for functionality at reduced protein/N requirement.
As a means of identifying key traits and dissecting relevant processes, WGIN 1 demonstrated the usefulness of mapping populations, principally the Avalon x Cadenza doubled haploid population. Initial trials indicated that whilst Cadenza parent lines out-performed Avalon in relation to NUE, the doubled haploid progeny lines demonstrated substantial transgressive segregation for all characteristics analysed. An example, measured nitrogen utilisation efficiency (in a single trial in 2007), is shown in the figure.
Further trials are required with this population at both low and high N inputs to validate and map the preliminary identified QTLs determined within WGIN 1. Furthermore a more detailed N response trial with a selected subset of lines encompassing an extensive analysis of plant component parts in terms of yield/N management/specific gene expression is required.
N-uptake is an essential component of overall NUE. Whilst overall N-uptake can be measured and NUpE estimated based on field soil data, it is difficult to breakdown the trait in field based experiments. Therefore we will investigate the variation in ability of seedlings (prior to GS30, to be confirmed experimentally) to take up N in a glass house-based experiments, in which fine control of both N-supply and seedling establishment can be achieved.
To ensure development of higher yielding wheats having the required properties for use in food processing, genes controlling grain functionality independently of protein content will be studied. This will be assessed by development of NILs (5 QTLs x 4NILs/QTL = 20 lines), using marker-assisted backcrossing of those bread making quality QTLs which are independent of protein content and known storage proteins. Replicated (x3) field trials will then be carried out for two years at 5N levels that span the current range used for growing wheats (100, 150, 200, 250, 300kg/Ha) followed by functionality analysis of selected samples (lab scale predictive tests, SE-HPLC and spiral white bread-making). Transcriptome profiling will be carried out on developing grain of selected NIL x N level combinations to identify transcripts and hence candidate genes for functionality at reduced protein/N requirement.
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