Abstract: Twelve rapeseed cultivars（lines） belonging to three types were used as experimental materials. Four treatments were established, including 40 mg/L uniconazole, 50 mg/L paclobutrazol,18.75 mg/L GA₃ and 30 mg/L GA₄. Spraying was conducted on the 7th day after rapeseed germination. Agronomic traits at the seedling and mature stages were determined, and cold tolerance and waterlogging tolerance of seedlings were evaluated. The results showed that the coefficient of variation for waterlogging tolerance was the highest. Treatments with uniconazole and paclobutrazol significantly reduced seedling height and main root length, and markedly increased lateral root number and leaf chlorophyll content. By contrast, GA₃ and GA₄ treatments substantially increased seedling height and main root length, but significantly inhibited lateral root number and leaf chlorophyll content. Overall, the sensitivity of seedling agronomic traits of different rapeseed genotypes to uniconazole, paclobutrazol and gibberellins ranked from high to low as: Chinese semi-winter female parent × winter male parent, Chinese semi-winter female parent × (Chinese semi-winter × European winter) DH male parent, and Chinese semi-winter female parent × Chinese semi-winter male parent. Stepwise regression analysis was performed between the response values of seedling traits to gibberellin treatments and seedling stress resistance as well as yield. The results indicated that yield-related traits had no correlation with the response values of seedling traits to gibberellins. The response value of seedling chlorophyll content to GA₄ was closely associated with seedling cold tolerance, and the response value of seedling chlorophyll content to GA₃ was significantly correlated with growth period. Additionally, the response values of root length and lateral root number to paclobutrazol were strongly related to waterlogging tolerance. In conclusion, rapeseed genotypes presented distinct differences in response to gibberellins. In practical production, gibberellin-related plant growth regulators could be adopted for classified regulation of seedlings of different rapeseed cultivars, so as to precisely improve the stress resistance of rapeseed seedlings.

Key words: rape (Brassica napus L.), genotypes, gibberellin, yield, agronomic traits, resistance