The frequency of heat shocks during grain filling of wheat crops across the Australian wheatbelt has significantly increased over the last 30 years.These post-flowering heat events significantly reduce wheat yields with a relatively greater impact on grain size than grain number.A controlled environment study was conducted to assess the impact of post-flowering heat shocks on Orthopedic wheat recombinant inbred lines SB062 and SB003.
Plants were submitted to 7-day heat shocks (33/21 °C day/night temperature) at different periods during grain filling.Heat shocks significantly accelerated leaf senescence, with a greater impact on older leaves and for mid post-flowering stresses.Overall, the tolerant line (SB062) could maintain leaf greenness longer than the sensitive line (SB003), especially when submitted to heat stress.
Further, heat shocks during early-to-mid grain filling reduced the grain size and weight.While the impact on developing grains was significant in SB003, no significant effect of post-flowering heat was observed on leaf senescence nor on grain size MYRRH GUM in the tolerant line SB062.Delayed leaf senescence appeared to play a role in maintaining grain size under heat stress.
The research findings will assist improving crop models for post-flowering heat effects and developing techniques for screening heat tolerant wheat lines.Increased post-flowering assimilate production through sustained leaf greenness could improve the performance of wheat crops in increasingly warmer environments.