Micro-nano ethylene bubbles water promotes anthocyanin accumulation in grapes by regulating endogenous ethylene and synergistic abscisic acid

Micro-nano bubbles (MNBs) technology has been widely applied in agriculture, but combining it with ethylene gas remains underexplored. In this study, 'Flame' seedless grapevines were treated with micro-nano ethylene bubbles water (C₂H₄-MNBs) and ethylene gas (EG), with distilled water serving as the control (CK). At 4, 7, 10, and 13 days, C₂H₄-MNBs significantly improved fruit coloration, anthocyanin content, and significantly elevated the activities of phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS). Moreover, endogenous ethylene and ABA levels were significantly upregulated at 4 days post-treatment. At 10 days, soluble solids, anthocyanin content, endogenous ethylene production, and ABA accumulation in the C₂H₄-MNBs treatment were all significantly higher than those in the EG treatment. Transcriptomic analysis revealed that several key genes involved in anthocyanin, ethylene and abscisic acid (ABA) metabolism were upregulated under C₂H₄-MNBs treatment. This study investigated the regulatory mechanism of C₂H₄-MNBs on grape coloration at the metabolic and transcriptional levels, demonstrating superior efficacy compared to ethylene gas.