Developing novel types of low protein wheat for breadmaking

Nitrogen fertiliser is essential to sustain wheat yields but is also an important determinant of grain quality. This is because nitrogen is required for the synthesis of grain proteins, with the gluten proteins forming the major grain protein fraction. About 40% of the wheat produced in the UK is used for food production, particularly for making bread and other baked products. Wheat is also widely used as a functional ingredient in many processed foods, while bread wheat and imported durum wheats are used to make noodles and pasta, respectively. The gluten proteins are essential for these uses, providing visco-elastic properties to dough. Consequently, the content and quality of the grain proteins affect the processing quality, with a minimum of 13% being specified for the Chorleywood Breadmaking Process (CBP) which is used for over 80% of the "factory produced" bread in the UK. The requirement of nitrogen to produce wheat for bread making is also above the optimum required for yield, and farmers may apply up to 50 kg N/Ha above the yield optimum to achieve 13% protein (2.28% N). This is costly with nitrogen fertiliser contributing significantly to crop production, and may also contribute to a greater "nitrogen footprint" in the farmed environment. It may be possible to reduce the requirement for breadmaking wheats, to a limited extent, by optimising the efficiency of nitrogen uptake and use within the wheat plant. However, this will only have limited benefits and a more viable long-term solution is to develop new types of wheat and processing systems which will allow the use of lower protein contents for bread making. We will therefore identify types of wheat which have good and stable breadmaking quality at low grain protein. Genetic analyses of the trait will provide molecular markers to assist wheat breeders while studies of underpinning mechanisms will allow new selection procedures to be used to identify germplasm and select for quality in breeding programmes. We will also work with millers and bakers to establish optimum conditions for processing of wheats with lower protein contents.

1. We will initially evaluate the performance of lines known to perform well at lower N contents, to determine their quality and stability at varying levels of nitrogen fertilisation.
Lines will include UK cultivars such as Hereward which has perceived high stability, German cultivars developed to perform well at low N, cultivars with high dough strength from Hungary and Serbia, lines with lower ratios of gliadin:glutenin and hybrid cultivars. These will be grown in replicate plots on three sites for two years with 150 and 200 kg N/Ha and their protein compositions and properties determined using a range of approaches, including milling, mixing and text baking in order to identify properties that relate to performance at low protein.
2. It is likely that currently used screening systems will not be appropriate for determining quality at low protein. We will therefore use the samples and data from the intital studies to evaluate current methods and develop new methods.
3. Genetic analysis will be carried out using selected cross populations grown in field trials at three sites for two years. Full functionality studies will be carried out on about 10% of the samples and rapid analyses on all samples. This will establish QTLs for quality at low protein and allow the establishment of KASP markers to enable wheat breeders to select for the trait. QTL-based models for the development of low protein wheat will also be developed, using QTL data for bread making quality to simulate segregating populations and identify target genotypes for optimum functionality.
4. A novel QTL-based approach will be used to design wheats with optimised processing properties, by combining favourable alleles at mapped loci for aspects of quality. Such optimised lines should perform better at low protein
5. Grain samples of selected lines grown with low nitrogen inputs will be provided to industry partners enable them to optimise the processing conditions for low protein wheat.

1. A minimum grain protein content of 13% is specified for the Chorleywood Breadmaking Process (CBP) which is used for over 80% of the "factory produced" bread in the UK. Using the generally accepted N-to-protein conversion factor of 5.7 for wheat grain it can be calculated that a yield of 10 tonnes of wheat will require a minimum of 228 kg on N per hectare to satisfy this requirement alone. In fact, although some additional nitrogen (up to about 50 kg/ Ha in the UK) may be available to the crop from atmospheric deposition and soil mineralisation, current varieties only take up about 80% of applied N (less at higher N applications), with N harvest indexes of 80-90%. Consequently, the requirement for applied N for 10 tonnes of wheat is between 300 and 350 kgN/Ha, which is above the current fertilisation rates. Reducing the requirement by 50kg/Ha will therefore have a significant impact on production costs, which will be passed up through the food chain from farmers to processors, retailers and consumers.

2. Although the apparent efficiency of nitrogen use by UK agriculture has been improving steadily over the past 25 years (AIC Fertiliser Statistics, 2013), further improvement is still required and reducing the N application to wheat will have significant environmental benefits by reducing the environmental footprint.

3. Reducing the protein content of bread making wheats will reduce the energy requirements (and hence the costs) for milling and baking.