Effects of IBA Combined with NAA/Melatonin/Citric Acid on Rooting Characteristics of Grape Rootstocks

HighlightsWhat are the main findings?We optimized novel IBA–melatonin (MLT) and IBA–citric acid (CA) compound rooting formulas for hardwood cuttings of seven grape rootstocks, with 400 mg/L IBA + 1.2 mM MLT screened as the optimal universal formula.The optimal MLT combination significantly improved root morphology, root activity and soluble substance accumulation, and balanced endogenous hormone levels in grape rootstock cuttings.Transcriptome analysis revealed that MLT promotes adventitious rooting mainly by regulating plant hormone signal transduction and MAPK signaling pathways in grape rootstocks.What are the implications of the main findings?The optimized formulas provide practical technical support for large-scale and standardized propagation of grape rootstocks.The clarified physiological and molecular mechanisms advance the theoretical research on rooting regulation of woody plant cuttings.This work provides a new reference for the application of MLT and CA as efficient rooting promoters in horticultural cutting propagation.Efficient rooting is essential for the propagation of grape rootstocks. This study aimed to identify an effective rooting formulation for hardwood cuttings and to investigate its underlying physiological and molecular mechanisms. Seven grape rootstocks were treated with indole-3-butyric acid (IBA) combined with melatonin (MLT) or citric acid (CA), with IBA plus naphthaleneacetic acid (NAA) and water serving as controls. Rooting performance was comprehensively evaluated using morphological traits, physiological characteristics, endogenous hormone contents, and transcriptome analysis. Among all treatments, 400 mg/L IBA combined with 1.2 mM MLT exhibited the best rooting performance. This treatment significantly enhanced root activity, soluble sugar, and soluble protein contents. It also increased IAA and GA3levels and improved the IAA/ABA and GA3/ABA ratios compared with the controls. Transcriptome analysis of ‘110R’ revealed that MLT-responsive genes were mainly enriched in plant–pathogen interaction, hormone signal transduction, and MAPK signaling pathways. Transcription factor families including MYB, ERF, and NAC were identified as potential regulators. Collectively, these findings demonstrate that IBA–MLT combined application promotes rooting by regulating physiological metabolism, hormone balance, and gene expression, providing a theoretical basis for improving grape propagation efficiency.