Lonicera caerulea L. has high nutritional and health value, and it is an important emerging small berry tree species. In this study, the morphology and nutrient composition of 60 cultivars were used to analyze and evaluate the diversity of the genus. Morphological analysis showed that the phenotypic traits of different cultivars had significant differences (p < 0.01). The phenotypic coefficient of variation (PCV) of each trait was 12.42%~84.06%, and the coefficient of genetic variation (GCV) was between 7.07%~71.72%. The analysis of nutrient content showed significant differences among the cultivars (p < 0.01). The PCV of each trait was 3.95%~96.10%, and the GCV was 0.13%~32.83%. Based on breeding objectives, cultivars with excellent growth and leaf quantitative traits, fruit quantitative traits and nutrient contents were selected through the method of comprehensive analysis of multiple characters. Traits of the selected varieties were all above average, and specific genetic gain was higher. At the same time, the selection of varieties was carried out according to flowering and fruiting phenology, which provided an indication for the breeding of improved varieties. In this study, growth, leaf and fruit quantitative traits, phenological period and nutrient components of different cultivars provided valuable information for the breeding of improved varieties.

The double-flowering phenotype is crucial for improving the ornamental value of flowering plants; this trait substantially enhances the varieties of Syringa vulgaris L. To date, no studies have examined the transcriptomics and metabolomics of key nodes in the flower bud differentiation of the single and double flowers of Syringa. This study investigated both the single and double flowers of S. vulgaris using a comprehensive, multifaceted analytical approach, including physiological assessments, transcriptomics, and metabolomics. The floral bud differentiation process can be divided into six distinct stages. Compared with the single flowers, the double flowers of S. vulgaris presented significant developmental delays during floral bud differentiation. Although there was no significant difference in the soluble protein content between the two flower types during this process, the soluble sugar content varied during pistil primordium differentiation and as temperature increased. The antioxidant enzyme activity was significantly greater in the double flowers than in the single flowers during most differentiation stages, while the malondialdehyde (MDA) level gradually increased. The levels of endogenous hormones, such as indole-3-acetic acid (IAA), gibberellin (GA₃), and abscisic acid (ABA), differed between the two flower types. The transcriptomics and metabolomics results indicated that during pistil primordium differentiation and subsequent development, the double flowers exhibited increased antioxidant enzyme activity and secondary metabolite accumulation. These secondary metabolites not only contributed to the vibrant coloration of the double flowers but also increased their cellular metabolic stability and stress tolerance through their antioxidant properties. Conversely, the rapid differentiation mechanism of the single flowers of S. vulgaris relied more on efficient primary metabolism to meet simpler structural demands. These findings not only provide scientific guidance for S. vulgaris breeding programs but also expand its potential in horticultural and landscape applications, offering a new theoretical foundation for studies on floral organ development in Oleaceae species.