The shifting influence of future water and temperature stress on the optimal flowering period for wheat in Western Australia.

An optimal flowering period (OFP) minimises the long-term combined risk of extreme weather events on crop yield and exists in all environments. With climate change, the frequency, timing and intensity of these events are likely to change, which in turn may shift the OFP. It is important to explore how the OFP would change under a future climate. Knowledge of the OFP is important for formulating breeding strategies and developing suitable varieties. Here, a simulation analysis was conducted at 4 sites in Western Australia to quantify any shift in the OFP due to climate change, by accounting for the effects of frost, heat and water stress on wheat yield. Three global climate models that projected the greatest precipitation decrease under the Representative Concentration Pathways 8.5 during 2061-2100 were ensembled to represent a dry future climate condition (dry scenario); and 3 models that predicted the smallest decrease in precipitation were ensembled to represent a wet future climate condition (wet scenario). The simulation results predicted that the timing of OFPs for wheat in Western Australia would occur earlier than the current OFP. On average the OFP was 29 days earlier in the dry scenario and 11 days earlier in the wet scenario. Early sowing of long-season varieties would be preferable to achieve the OFP in both climate scenarios due to greater yield potential. Early sowing opportunities were very limited under the dry scenario, and therefore fast maturing varieties for late sowing would also be necessary.