Integrated Morphological, Transcriptomic, and Metabolomic Profiling Reveals Differential Development Mechanisms in Two Weeping Forsythia Genotypes during Tissue Culture

Weeping forsythia ( Forsythia suspensa ) is an important medicinal and ornamental plant. To explore genotype-dependent growth variation under tissue culture, we compared two long-style genotypes, FLS-1 and FLS-2. FLS-1 exhibited reduced plant height, branching, internode length, and chlorophyll content, along with chlorosis and impaired chloroplast ultrastructure. Transcriptomic analysis identified 2,059 and 3,482 DEGs between FLS-1 and FLS-2 on days 25 and 35, respectively, with 46 DEGs related to photosynthesis. Metabolomic profiling revealed 563 DEMs, with 15 KEGG pathways significantly enriched. These results elucidate key molecular differences affecting growth and photosynthesis between F. suspensa genotypes in vitro.