Regulatory role of exogenous 24-epibrassinolide on tomato fruit quality

Abstract Background Brassinosteroids (BRs) are known to regulate fruit development, ripening, and metabolic processes in plants. In this study, the impact of exogenous 24-epibrassinolide (EBR) on tomato fruit quality was examined using ‘Micro-Tom’ tomatoes. Results Treatments included control (CK), EBR, and brassinazole (Brz, BR biosynthesis inhibitor). EBR application accelerated fruit ripening, evidenced by decreased fruit hardness and increased soluble solids and vitamin C (VC) content. EBR enhanced glucose and fructose accumulation and upregulated key genes involved in sugar metabolism ( SS , NI , SPS , AI ). Conversely, Brz treatment inhibited these effects. EBR also reduced malic and citric acid levels by downregulating genes associated with acid metabolism ( CS , PPC1 , PPC 2, MDH ), while Brz increased acid content. Furthermore, EBR significantly elevated flavonoid compounds, such as rutin and quercetin, and altered volatile profiles as detected by electronic nose analysis, particularly affecting W2W and W5S sensors. Conclusion These results indicated that EBR could effectively modulate sugar and acid metabolism, enhance flavonoid content, and influence fruit aroma, suggesting its potential to improve tomato fruit quality.