Rapeseed is the largest self-produced oil crop in China which plays an important role in ensuring the safety of edible oil. However, its current per unit yield is far below Canada and Europe. In this study, selenium fertilizer and other micro fertilizers were sprayed on Xiangzayou 787 at the seedling stage. The results showed that the yield per plant increased 24.3% with sprayed selenium compared to the control (CK). Compared with the CK, the chlorophyll content in leaves at the flowering stage was significantly increased by 20.8%, and the soluble sugar content in the silique wall and seeds at the maturity stage was significantly increased and increased by 62.1% during the budding stage. The functional leaves of Xiangzayou 787 with the sprayed selenium fertilizer and the CK were used as raw materials for absolute quantitative transcriptome sequencing analysis. Accompanied with bioinformatics analysis, six differential genes which affect growth were discovered. The expression level of the protein phosphatase 2C gene in the silique wall was significantly higher than that of the CK. The PP2C78 gene was significantly positively correlated with the chlorophyll and soluble sugar content in leaves and the correlation coefficients were 0.539 and 0.547. According to gene expression levels, yield, and physiological indicators, PP2C78 may be a key functional gene affecting rapeseed yield. In this study, selenium fertilizer was found to be an excellent foliar fertilizer for rapeseed; the PP2C78 gene may be helpful for analyzing the yield increasing mechanism and used as a reference for screening new foliar fertilizers.

China’s edible oil self-sufficiency rate is only about 30%, and approximately 100 million acres of saline-alkali land are potentially available for rapeseed cultivation. However, salt stress severely inhibits rapeseed growth and yield, making the breeding of salt-tolerant varieties and the study of underlying molecular mechanisms urgent priorities. In this study, 1609 Brassica napus accessions were screened for salt tolerance, and the highly salt-tolerant material ‘Xiangnong Saline-Alkali Oil No. 1’ (XNSA01) was identified. Subsequent physiological, hormonal, transcriptomic, and functional analyses were conducted to characterize its salt-tolerance mechanisms. Salt stress significantly activated antioxidant defense and stress-related hormone responses in XNSA01, accompanied by significant accumulation of proline, abscisic acid, and salicylic acid. Transcriptome analysis identified five candidate salt-responsive genes, among which BnaA10g15320D, BnaA02g04730D, and BnaC07g08360D were closely associated with antioxidant enzyme activities and endogenous hormone contents. In particular, BnaA02g04730D showed a significant negative correlation with MDA content. Yeast heterologous expression and transgenic validation further demonstrated that BnaA02g04730D enhanced salt tolerance by increasing antioxidant enzyme activities and reducing membrane lipid peroxidation. These findings provide a useful basis for the breeding of salt-tolerant rapeseed varieties and for further investigation of salt-tolerance mechanisms in B. napus.