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.

Water is a primary element restricting the growth and survival of trees; thus, drought stress has a negative impact on plant development. In the current study, the transcriptional and metabolic changes in Populus davidiana were investigated under drought stress. We found that the chlorophyll content of poplars decreased, and reactive oxygen species (ROS) accumulation increased during drought stress. Following 2, 4, 6, 8, and 10 d of drought stress, 2127, 5334, 8894, 11,279, and 11,778 differentially expressed genes (DEGs) were identified, according to transcriptome analysis results. Enrichment analysis showed that a large number of DEGs were enriched in photosynthesis, chlorophyll decomposition and synthesis, and secondary metabolism-related pathways. The results of metabolomics analysis indicate that 131, 378, 334, 365, and 646 metabolites accumulated differentially following 2, 4, 6, 8, and 10 d, respectively, of drought stress. According to K-means clustering analysis, the contents of flavonoids significantly decreased alongside gene expression levels, while lipid content increased at 10 d of drought stress, alongside most of the related gene expression levels. Based on these data, two gene regulatory networks (GRNs) for lipid metabolism and flavonoid synthesis were constructed, each containing 45 transcription factors (TFs). Among them, six TFs (ERF39, GAI, ERF34, DOF5.2, DREB2A, and C3H6) were shared by two GRNs, suggesting that they may have diverse functions in response to drought stress. In summary, this study provides candidate genes for cultivating drought-resistant varieties and offers new insights into enhancing that resistance.

The Short Internodes-Related Sequence (SRS) family is a class of transcription factors unique to plants that are essential for controlling their growth, development, and stress responses. Nevertheless, information regarding the characterization and biological function of poplar SRS family members remains limited. In this study, we identified 10 members of the SRS gene family in the genome of Populus tremula using bioinformatics, distributed on seven chromosomes and named PtSRS01-PtSRS10 based on their locations. Our phylogenetic analysis results indicated that PtSRS genes can be categorized into five subfamilies and that members of each subfamily have similar gene structures and motifs. Collinearity analysis indicated that the expansion of the PtSRS gene family is caused by segmental duplication and is influenced by purifying selection during its evolutionary process. Cis-acting element analysis revealed that PtSRS was enriched in cis-acting elements related to growth and development, light response, hormone induction, and stress response. Quantitative real-time PCR revealed that drought and salt (NaCl) treatments affected the expression of several PtSRS genes, with PtSRS04 and PtSRS05 being the two genes with the most significant expression levels, with PtSRS04 showing a 700-fold increase in relative gene expression level after 8 d of drought stress and the PtSRS05 gene showing a 38-fold increase in gene expression level at 48 h of NaCl stress, suggesting that they could be crucial in salt and drought stress. The results presented herein provide a theoretical basis for subsequent in-depth studies on the involvement of poplar SRS gene family members in drought and salt stress resistance.