Winter canola (Brassica napus L.) is highly sensitive to increasing temperatures during the reproductive and pod‐filling stages. Although the impact of high day‐time temperature stress on yield and quality has been documented in canola, similar information under high night‐time temperature (HNT) stress is not available. Using six hybrids and four open‐pollinated cultivars, we observed a marked shift in peak flowering towards earlier, cooler hours of the morning under HNT. Averaged across two independent experiments, the photochemical efficiency of photosystem II was significantly decreased (3%), with a significant increase in thylakoid membrane damage (13%) in the leaves of susceptible cultivars under HNT stress. Similarly, the susceptible cultivars also recorded significant reduction in biomass (34%), pod number (22%), pod weight (37%) and total seed weight (40%) per plant while the same set of agronomic traits were not affected among the tolerant cultivars. Quantitative impact of heat stress was confirmed with increased sensitivity to HNT exposure from gametogenesis until maturity resulting in a significantly higher yield loss compared to stress exposure from post‐flowering till maturity. HNT significantly decreased oil concentration, but increased protein concentration and saturated fatty acid levels in seeds of the susceptible cultivars. However, HNT had no impact on the unsaturated fatty acids in both hybrids and the open‐pollinated cultivars. Breeding targets based on fatty acid composition for enhancing canola seed quality may not be easily amenable due to the inconsistency documented with the compositional changes under heat stress. In summary, our findings conclude that canola hybrids are better suited to regions experiencing heat stress, compared to open‐pollinated cultivars, indicating the possibility of a complete shift to hybrid canola cultivation under predicted hotter climates in the future.

中文翻译：

---

开花期和荚果灌装期间的夜间高温会影响油菜的开花，产量和种子脂肪酸组成

冬季油菜（甘蓝型油菜 L.）对生殖和荚果填充阶段的温度升高高度敏感。尽管油菜籽中记录了白天高温胁迫对产量和品质的影响，但在夜间高温（HNT）胁迫下没有类似的信息。使用六个杂种和四个开放授粉的品种，我们观察到在HNT的作用下，开花高峰明显向着清晨，凉爽的时间转移。在两个独立实验中取平均值，在HNT胁迫下，易感品种叶片中光系统II的光化学效率显着降低（3％），类囊体膜损伤显着增加（13％）。同样，易感品种也记录到生物量（34％），豆荚数（22％），每株植物的荚果重量（37％）和种子总重量（40％），而相同的农艺性状不受耐性品种的影响。与从开花后到成熟的胁迫暴露相比，通过配子发生直至成熟对HNT暴露的敏感性增加，证实了热胁迫的量化影响。HNT显着降低了油料浓度，但增加了易感品种种子中的蛋白质浓度和饱和脂肪酸水平。然而，HNT对杂种和开放授粉品种的不饱和脂肪酸均无影响。基于脂肪酸组成的用于提高油菜籽质量的育种目标可能不容易接受，因为在热胁迫下与组成变化有关的不一致。综上所述，