Crop management strategies for low asparagine grains to limit acrylamide-forming potential

Acrylamide is a Group 2A carcinogenic chemical that forms from free asparagine and reducing sugars during the frying, baking, roasting and toasting of foods derived from grains, tubers, beans and other crop products. Free asparagine concentration determines the amount of acrylamide that forms in cereal products. Free asparagine concentration differs between wheat varieties but is also highly responsive to environmental and crop management factors, including the level of fertilization provided to the crop. The student will look at the role of nitrogen and sulphur fertilization, and determine the effects of other minerals, irrigation and disease. He/she will investigate diurnal regulation of asparagine synthesis and breakdown in wheat, looking at both asparagine synthetases (formation of asparagine) and asparaginases (asparagine breakdown). A soft wheat mapping population will be analysed to identify QTL for free asparagine concentration, and varieties will be screened for the presence/absence of an asparagine synthetase-2 gene on Chromosome 3B: this gene has been shown to be missing in some varieties, and the effect of the loss of this gene on free asparagine concentration in the grain will be investigated. The student will also compare the performance of low and high asparagine grains in biscuit production lines. Low, medium and high asparagine soft wheat varieties will be grown in field trials at the Rothamsted Woburn farm site and at Mondelez sites in France. The trials will investigate the effects of different nitrogen: sulphur ratios on free asparagine concentration, the effects of other minerals, and the importance of irrigation and disease control. The trials will run for three years, with funding provided by Mondelez. The student will oversee the trials, including working with a statistician on designing the trials and analysing the data. The student will also visit the Mondelez laboratory in Reading RSSL to analyse free asparagine in grain samples from the trials.
Differential sulphur responses between varieties. There are not only varietal differences in free asparagine concentration per se but also in the response of free asparagine to sulphur, with some low asparagine varieties showing the largest increases under sulphur deficiency. The student will investigate the molecular basis of these responses.

Diurnal regulation
Asparagine synthesis and breakdown has been shown to be diurnally regulated in Arabidopsis, with different asparagine synthetases active during the day and night. The student will investigate this phenomenon in different wheat tissues, including grain: which enzymes/genes are diurnally regulated, in which tissues; is asparagine synthesis and breakdown diurnally regulated in the grain and for how long during development?

Asparaginases
Wheat grain naturally contains asparaginase enzymes. The student will investigate why these enzymes fail to prevent the accumulation of free asparagine, and the potential for activating them by application of a plant growth regulator.

Mapping population.
We have produced a soft wheat (Claire x Robigus) mapping population in collaboration with the John Innes Wheat Genetics Group. This population is being grown annually at JIC and grain will be made available free of charge for analysis. Measurement of free asparagine in the grain of the lines in the population could enable the student to identify QTL controlling this important trait.
Deletion of B genome TaASN2 gene.
The student will compare low, medium and high asparagine grains in the manufacture of small-scale biscuits at the Mondelez R&D Centre in Saclay, near Paris, assessing the importance of free asparagine concentration in the raw material relative to other aspects of the process, the relative functionality of different grains, and how much free asparagine is used up in a typical manufacturing process. Acrylamide formed in the biscuits will be measured at the Mondelez laboratory in RU RSSL.