Investment

It has been recently established that the application of nitrogen fertilisers across the Western Australian wheat belt can increase wheat grain yield and protein content simultaneously under specific types of nitrogen management involving in season fertilizer application (Nicol et al submitted). However, the rate of protein degradation in wheat tissues and grain during development has never been tested in the field or in conjunction with nitrogen application parameters. Interestingly, new technology developed at the University of Western Australia using progressive labelling of plants with 15N has revealed that 25% of wheat protein is 'futile cycled' during wheat grain development in the controlled environment conditions. This indicates a 25% loss of protein synthesised in the grain from the final grain protein content due to protein degradation in the grain (Cao et al 2021). Futile cycling is an energy expensive process that potentially limits net nitrogen uptake and net nitrogen utilization during early grain development. A far better understanding of the biology of grain protein production is needed to turn around the steady decline in protein levels in WA wheat that are now nearly always the lowest in Australia. While environmental factors and water availability are contributing factors to wheat development, the outcomes of how nitrogen management programs effect protein content and yield is often unpredictable. This is due in part to our limited knowledge of factors influencing the biological processes between nitrogen assimilation in leaves and accumulation in grain protein. These biological processes are largely treated as a black box in current nitrogen management. The innovation of this project will be to experimentally address a critical missing element of how the amount of nitrogen applied and time of application influences the rate of protein accumulation in the developing grain, by measuring protein synthesis and protein degradation during grain development.