Increasing wheat yield and yield stability through improved heat tolerance during grain filling

⁠⁠⁠Heat stress is recognised by Australian growers as a significant constraint on yield potential. Growers make decisions around sowing time, input use and variety choice to balance the risk of frost avoidance and heat stress induced loss of yield. If the heat tolerance of wheat varieties could be increased this would provide growers with greater flexibility regarding sowing decisions to avoid frost, while maintaining yield potential despite warmer climates.

There are two critical periods of development in cereals that are sensitive to heat stress events: late stage floral development and grain filling. Heat stress during late stage floral development results in loss of grain number through pollen sterility and floret abortion. Heat stress events during grain filling result in smaller grain and hence reduced yield and increased downgrades. Grain filling heat events occur more frequently than those during late stage floral development and as such have a larger impact on final crop yield on average across Australia. Previous GRDC investments have successfully improved the heat tolerance of wheat during late stage floral development.

This tender is for a R&D partnership between commercial wheat breeders and academic researchers to undertake a pre-breeding project to improve the heat tolerance of wheat during grain filling across the diversity of Australian wheat growing environments. It is expected that this project will identify and collate genetic diversity for tolerance to heat events during grain filling, then develop pre-breeding germplasm and genomic selection tools that can be used by Australian breeders to improve the heat tolerance of new wheat varieties. A secondary aim of the project is to advance pre-breeding and breeding technologies so as to maximise the efficiency and efficacy of adoption of pre-breeding outputs by breeding companies, and hence the flow through of the impact of investment to Australian grain growers. Consideration of time-bound exclusivity in the use of outputs by participating wheat breeding companies will be dependent on the proposed contribution to the project of the breeding company including their levels of co-investment. 

Expected Outcomes

Overall Outcome: By 2035, growers are able to maintain and increase wheat yields, and minimise downgrading, through access to new wheat varieties better adapted to heat stress during grain filling.

Intermediate Outcome: By 2026, Australian wheat breeders have access to adapted pre-breeding germplasm, and associated selection tools, with a minimum 10% improvement in ability to maintain grain weight under heat stress when introgressed into elite breeding germplasm.

Expected Outputs

Output 1.

By 2026, a minimum of five adapted wheat pre-breeding lines developed with at least 10% higher yield than the current highest yielding cultivars under heat stress during grain filling. Lines to be enriched for heat tolerance at grain filling based on genomic predictions and field-based phenotypes in at least five environments and passed onto breeders with genomic information for selection.