Citrus reticulata ‘Chachi’ (CRC) has long been recognized for its nutritional benefits, health-promoting properties, and pharmacological potential. Despite its importance, the bioactive components of CRC and their biosynthetic pathways have remained largely unexplored. In this study, we introduce a gap-free genome assembly for CRC, which has a size of 312.97 Mb and a contig N50 size of 32.18 Mb. We identified key structural genes, transcription factors, and metabolites crucial to flavonoid biosynthesis through genomic, transcriptomic, and metabolomic analyses. Our analyses reveal that 409 flavonoid metabolites, accounting for 83.30% of the total identified, are highly concentrated in the early stage of fruit development. This concentration decreases as the fruit develops, with a notable decline in compounds such as hesperetin, naringin, and most polymethoxyflavones observed in later fruit development stages. Additionally, we have examined the expression of 21 structural genes within the flavonoid biosynthetic pathway, and found a significant reduction in the expression levels of key genes including 4CL, CHS, CHI, FLS, F3H, and 4′OMT during fruit development, aligning with the trend of flavonoid metabolite accumulation. In conclusion, this study offers deep insights into the genomic evolution, biosynthesis processes, and the nutritional and medicinal properties of CRC, which lay a solid foundation for further gene function studies and germplasm improvement in citrus.

Australian finger lime (Citrus australasica L.) has become increasingly popular due to its potent antioxidant capacity and health-promoting benefits. This study aimed to determine the chemical composition, antibacterial characteristics, and mechanism of finger lime extract. The finger lime extracts were obtained from the fruit of the Australian finger lime by the ethanol extraction method. The antibacterial activity of the extract was examined by detecting the minimum inhibitory concentration (MIC) for two Gram-positive and four Gram-negative bacterial strains in vitro, as well as by assessing variations in the number of bacteria for Candidatus Liberibacter asiaticus (CLas) in vivo. GC-MS analysis was used to identify the antibacterial compounds of the extract. The antibacterial mechanisms were investigated by assessing cell permeability and membrane integrity, and the bacterial morphology was examined using scanning electron microscopy. The extract demonstrated significant antibacterial activity against Staphylococcus aureus, Bacillus subtilis, and Gram-negative bacterial species, such as Escherichia coli, Agrobacterium tumefaciens, Xanthomonas campestris, Xanthomonas citri, and CLas. Among the six strains evaluated in vitro, B. subtilis showed the highest susceptibility to the antimicrobial effects of finger lime extract. The minimum inhibitory concentration (MIC) of the extract against the tested microorganisms varied between 500 and 1000 μg/mL. In addition, the extract was proven effective in suppressing CLas in vivo, as indicated by the lower CLas titers in the treated leaves compared to the control. A total of 360 compounds, including carbohydrates (31.159%), organic acid (30.909%), alcohols (13.380%), polyphenols (5.660%), esters (3.796%), and alkaloids (0.612%), were identified in the extract. We predicted that the primary bioactive compounds responsible for the antibacterial effects of the extract were quinic acid and other polyphenols, as well as alkaloids. The morphology of the tested microbes was altered and damaged, leading to lysis of the cell wall, cell content leakage, and cell death. Based on the results, ethanol extracts from finger lime may be a fitting substitute for synthetic bactericides in food and plant protection.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a vector of Candidatus Liberibacter asiaticus (CLas), the causal agent of citrus Huanglongbing (HLB). We examine the effectiveness of spraying adhesive on new shoots of orange jasmine (Murraya paniculata) to trap ACP in laboratory and field conditions and for the monitoring of ACP population dynamics and directional preferences. After 36 h of observation, orange jasmine plants with new shoots, with and without adhesive, are significantly (p < 0.05) more attractive to ACP than plants without new shoots. In field trials, orange jasmine with new shoots attracted more ACP, particularly females, than plants without new shoots. A male-biased ACP sex ratio occurred in a near-natural population. Orange jasmine with new shoots coated with adhesive more effectively trapped ACP than yellow sticky traps, particularly during the winter and early spring, when ACP densities were low. ACP has a strong phototropic response, preferring to feed and rest in south- and east-facing positions. Adhesive trapping shows potential for attracting adult ACP, especially in citrus orchards during cooler seasons, when host trees lack new shoots, and it may be particularly effective in doing so in urban areas and unmanaged citrus refugia (the primary sources of ACP infestations for commercial groves).

The plant microbiome plays important roles in plant growth and resistance, but its assembly and affecting factors have not been fully studied for most of the agricultural plants. In this study, the endophytic mycobiota of the leaves and roots and the rhizosphere soils of five pummelo varieties were profiled based on the amplicon sequencing of the fungal internal transcribed spacer (ITS). The fungal richness and diversity were significantly different among the compartments, but not among the pummelo varieties. The composition and structure of the endophytic mycobiota of the compartments were significantly different across all five pummelo varieties. These suggest that the variety effect is weaker than the compartment effect, but still significant in shaping the pummelo mycobiota. Specifically, the dominant leaf endophytic fungal taxa (e.g., Fusarium and Zasmidium), and the root selection of fungal genera from the rhizosphere soils, were significantly different among the varieties. And also, the variety effect is more significant in shaping the leaf endophytic mycobiota than those of the roots. Finally, the pummelo varieties also showed some consistent alterations on the endophytic mycobiota, such as the root enrichment of Exophiala species. Our study indicates that the endophytic mycobiota of pummelos is significantly and interactively affected by plant variety and compartment effects, and suggests some fungi of interest for further tests.