Researchers have unlocked the genetic secrets of improved nitrogen use efficiency and grain protein in wheat.

Key points

• Australian wheat varieties typically have low nitrogen use efficiency and grain protein due to poor soils and variable rainfall
• Researchers at Murdoch University have identified genetic clusters associated with higher grain protein and yield
• Genetic markers and breeding material will be made available to Australian breeding programs

Wheat profitability depends on achieving the ultimate combination of high yield and high grain protein content. However, nitrogen use efficiency and protein content in Australian wheat is typically low due to poor soils and irregular rainfall.

Traits that are expected to lead to better protein content without compromising yield are targeted by Australian breeding programs, but protein is a complex beast that is controlled by multiple genes.

To calculate nitrogen use efficiency, the team  at Murdoch University measured the total amount of nitrogen partitioned in the wheat grain – the nitrogen remobilised from leaf to grain – as a proportion of the available nitrogen in the soil. This makes nitrogen use efficiency a key indicator of simultaneously increased wheat grain protein content and yield.

Nitrogen use efficiency can be influenced by multiple different genetic factors that are typically measured by breeding programs.

Since 2015, GRDC has invested in research at Murdoch University to identify gene clusters associated with improved nitrogen use efficiency and to provide this genetic material, along with molecular markers, to Australian wheat breeders.

Better breeding

The project has been completed, with more than 20 different gene clusters identified, which contribute to improving grain protein content and yield through multiple processes within the plant.

The university has worked directly with Australian wheat breeders, whose advice has been valuable in guiding research directions. The project has also supported 10 PhD students to build future capacity in this area.

The team started with two wheat varieties with high grain protein content – LRPB Spitfire from Australia and Bethlehem from Israel.

These were crossed with high-yielding Australian varieties, such as Mace, Westonia and Suntop, to create six double-haploid populations – the genetically pure or ‘inbred’ lines used in breeding.

With the goal of identifying genetic material that combines high yield with high protein, the six crosses along with LRPB Spitfire and Bethlehem were grown at four field sites with distinct environments. Up to 22 traits associated with high grain protein content were measured at the sites at Muresk and Williams in Western Australia and Narrabri in New South Wales in 2018, and Beverley, WA, in 2020.

Quantitative trait locus (QTL) analysis, a statistical method that matches gene clusters to trait measurements from the field, was used to identify clusters that can improve both yield and protein content. These genes are not only effective independently but have an additive affect when applied in tandem.

At least three genes that simultaneously drive grain protein and yield will be made available to Australian breeding companies. More are under investigation.

More information: Professor Wujun Ma, 08 9360 6836, w.ma@murdoch.edu.au