Transcriptomic Analysis of the Effect of Combined Treatment with 1-Methylcyclopropene and 2,4-Epibrassionolide on the Postharvest Senescence of Fresh Daylily (Hemerocallis citrina)

In this experiment, we used different doses of 1-methylcyclopropene (1-MCP), 2,4-epibrassionolide (EBR), and their combination to treat fresh daylily and conducted a 15-day storage experiment at -1 to 1 ℃. By measuring physicochemical indicators and conducting transcriptomic analysis, the effects of 1-MCP and/or EBR on the postharvest senescence of fresh daylily were studied. The results indicated that combined treatment with 1 μL/L 1-MCP and 1 mg/L EBR after harvest was more effective in delaying adverse changes, such as yellowing, elongation, softening, dispersal, mass loss, and chlorophyll degradation, thereby greatly maintaining the storage quality of fresh daylily. Transcriptomic analysis revealed that the combined treatment regulated the transcription levels of senescence-related genes in daylily; significantly inhibiting the transcription of genes related to the ethylene biosynthesis and signal transduction pathways while activating the transcription of genes related to the brassinolide biosynthesis signal transduction pathway, therefore altering the metabolic balance of growth and senescence hormone levels in daylily. The combined treatment inhibited the transcription of genes related to the chlorophyll degradation pathway, which was beneficial for maintaining the quality of fresh daylily. Additionally, the combined treatment inhibited the transcription of E3 ubiquitin ligase genes closely related to senescence, thereby delaying protein degradation and postponing the physiological process of postharvest senescence in fresh daylily. This study provides a theoretical basis and practical reference for delaying the postharvest senescence and maintaining the storage quality of fresh daylily flower buds.