Mechanism analysis of uniconazole pretreatment improving waterlogging tolerance of different genotypes of Brassica napus L.

Background As a high-efficiency and low-toxicity triazole plant growth regulator, uniconazole alleviates various abiotic stresses of plants. Waterlogging seriously restricts the high-quality development of China’s rapeseed production. Although the mechanism of uniconazole improving the waterlogging tolerance of rapeseed remain elucidated, uniconazole was used in waterlogging stress. Results To explore the mechanism, waterlogging-sensitive cultivar ZS6 and waterlogging-tolerant cultivar HYZ50 were treated with uniconazole and waterlogging. The results showed that the mechanism of uniconazole improving waterlogging tolerance of rapeseed varied with varieties. Integrated metabolomic and transcriptomic analysis revealed that the sensitive cultivar tended to employ short-term emergency defense, whereas the tolerant cultivar achieved long-term adaptation via homeostatic regulation. Uniconazole pretreatment activated the stress response pathway in ZS6, but reinforced cell wall integrity and oxidative defense in HYZ50. Uniconazole pretreatment activated the stress response pathway, facilitating the specific enrichment of DEGs and DEMs in the linoleic acid metabolism, α-linolenic acid metabolism, and phenylalanine metabolism pathways in ZS6. ZS6 exhibited weak basal waterlogging tolerance, characterized by impaired antioxidant capacity, membrane repair efficiency, and osmotic regulation, thereby rendering it more susceptible to waterlogging-induced damage. Root activity exhibited an upward trend in ZS6, but lower than that in HYZ50. Soluble sugar content first decreased and then increased. Photosynthetic pigments displayed an upward trend, but the overall level is low compared with than in ZS6. In contrast, HYZ50 displayed robust waterlogging tolerance. Conclusion Uniconazole pretreatment modulated the phenylpropanoid biosynthesis pathway to reinforce cell wall integrity and augment oxidative defense, while coordinating tryptophan metabolism to sustain root function and signal transduction. This study established novel metabolic regulatory pathways for cultivar-specific waterlogging tolerance in B. napus .