It was found that there were significant genetic differences between Chinese and European Brassica napus lines, and the yield advantage of hybrid F₁ was obvious. To explore the effect of gibberellin (GA) on the growth and development of B. napus, the dynamic changes of GA during the developmental process of B. napus from different lines were measured. For explaining the role of GA in the formation of yield, the transcriptional levels of key enzyme genes involved in GA synthesis were analyzed, and the relationship between GA content and yield in parents and F₁ was clarified.

The dynamic changes of GA content in B. napus lines (15 Chinese lines and 15 European lines) with different sources from November 2020 to May 2021were determined using high performance liquid chromatography. Two F₁hybrid lines (YG2009×YC4, ZS11×YC4) with strong heterosis and their parents were used as materials to investigate the changes of GA content in different periods (D1, 15 January 2022; D2, 15 February 2022; D3, 15 March 2022)and measure growth indicators (plant height, root length, fresh weight, etc.), yield and component factors (silique number per plant, seed number per silique and thousand-seed weight), as well as photosynthetic indicators (photosynthetic rate, stomatal conductance, transpiration rate and intercellular CO₂ concentration).The change trend of GA content with temperature and the relationship between GA content and agronomic characters, photosynthetic characteristics and yield of parents and F₁hybrid from November 2021 to May 2022 were analyzed. Besides, the transcriptional levels of key enzyme genes involved in GA synthesis of the parents and F₁ at different stages (D1, D2, D3) also examined by quantitative real-time PCR.

The content of GA was closely related to the ambient temperature, and the GA content in the tested B. napus lines decreased first and then increased with the change of temperature. However, it was found that the average content of GA in B. napus lines from Europe was higher than that of Chinese lines. F₁ showed significant yield heterosis. Compared with the male and female parents, the yield of YG2009×YC4 and ZS11×YC4 increased by 18.06% and 10.35%, and 29.92% and 28.6%, respectively. There were significant differences in agronomic traits between parents and F₁, and the yield was correlated with GA content. The results also showed that the transcriptional levels of GA20ox4, GA3ox2 and SLR1 in parents and hybrid F₁ varied greatly.

The GA content of B. napus lines from Europe was more sensitive to temperature changes, but its average content of GA was higher than that from China. The yield of F₁ between European rape and Chinese rape lines showed strong heterosis, which was correlated with GA content. The transcriptional levels of GA20ox4 and GA3ox2 regulated the GA content.