Effects of long-term high-temperature stress on reproductive growth and seed development in development inBrassica napus

Brassica napus is the second most important oilseed crop worldwide. Increasing average temperatures and extreme weather have a severe impact on rapeseed yield. We determined the response of three cultivars to different temperature regimes (21/18 °C, 28/18 °C and 34/18 °C), focusing on the plant appearance, seed yield, seed quality, seed viability, and embryo development. Our microscopic observations identified that embryo development is affected by high temperatures. We noticed an acceleration of its development, in addition to pattern defects. Reduced fertilization rate, increased abortion rate, and preharvest sprouting would be responsible for the low seed yield at the high-temperature regime. Hormone profiling indicates that reduced auxin levels in young seeds may cause the observed embryo pattern defects. Moreover, reduced seed dormancy may result from low ABA and IAA levels in mature seeds. Glucosinolates and oil composition measurements suggest reduced seed quality. These identified cues help understand seed thermomorphogenesis and pave the way to the development of thermoresilient rapeseed plants. Highlight Brassica napus flowering plants’ growth at high temperatures accelerates embryo development, causing a high seed abortion rate and reduced seed quality. Temperature-reduced ABA levels cause premature seed sprouting.