Differential effects of temperature and duration of heat stress during anthesis and grain filling stages in rice

Heat stress can occur during different plant development stages, and understanding the impact of post-anthesis heat stress on grain yield in rice could help to improve the predictive accuracy of growth models. We performed temperature-controlled experiments in phytotrons to investigate this using two different heat-sensitive japonica rice cultivars at four daily maximum/minimum temperature regimes of 32 degrees C/22 degrees C (T1), 35 degrees C/25 degrees C (12), 38 degrees C/28 degrees C (T3) and 41 degrees C/31 degrees C (T4) and temperature durations of 2 (D1), 4 (D2) or 6 days (D3) at both anthesis and 12 days after anthesis (12DAA). Heat stress at anthesis caused a marked decrease in spikelet fertility and grain filling duration, but the 1000-grain weight was not obviously affected. Compared with T1D2 controls, treatment T4D3 decreased spikelet fertility and grain filling duration by 61.1% and 14 days, respectively. Heat stress at anthesis limited grain growth by inhibiting dry matter translocation rather than diminishing photosynthetic production. Heat stress (T4D3) at 12DAA was less disruptive but still decreased spikelet fertility by 29.2%, 1000-grain weight by 30.2%, and grain filling duration by 9.5 days. Leaf photosynthesis and leaf area were also diminished, which restricted the supply of materials for grain growth, although increased dry matter translocation partially compensated to reduce overall grain yield losses. Heat stress at higher temperature but shorter duration was comparable to lower temperature but longer duration. Heat stress at anthesis and 12DAA decreased average grain yield by 3.4%/degrees C/day and 2.3%/degrees C/day in Nanjing 41 and by 3.2%/degrees C/day and 1.7%/ degrees C/day in Wuxiangjing 14, respectively. Heat tolerance was generally higher in Wuxiangjing 14 than in Nanjing41. These results could improve the accuracy of crop models under heat stress and assist heat tolerance rice breeding programs. (C) 2016 Elsevier B.V. All rights reserved.