Establishment of a High-Efficiency Protoplast Isolation and Transient Transformation System for Chrysanthemum Petals

Chrysanthemum (Chrysanthemum × morifolium Ramat.) is a globally popular ornamental plant, but most cultivars lack efficient petal-based transient transformation systems, limiting floral trait molecular mechanism exploration. Protoplasts are versatile tools for gene localization, interaction, and functional characterization. Here, we established a petal protoplast isolation and transient transformation system for C. morifolium ‘Wandai Fengguang’ via L9(34) orthogonal design: optimal isolation (0.6 M mannitol, 8 h enzymatic digestion time, 0.4% macerozyme R-10, 4% cellulase R-10) and transformation (40% PEG4000, 12 μg plasmid, 10 min transfection, a protoplast density of 1 × 106 protoplasts mL−1). Under these conditions, protoplast yield was 5.14 × 106 protoplasts g−1·FW, viability 87.41%, and transformation efficiency 51.50%, with good applicability for six additional germplasms. We further analyzed CmVIT1 protein localization. Compared with the previous system, this system significantly improved protoplast yield and transformation efficiency, facilitating the transient transformation of genes related to floral traits in chrysanthemum and providing a methodological framework for other horticultural crops.