Plums are widely consumed, contain high levels of phenolic compounds, and have strong antioxidant activity. In this study, the main Sichuan cultivars ‘Qiangcuili’ and ‘Cuihongli’ were used to study the changes in the appearance, internal quality, phenolic compounds, and antioxidant activities during fruit development and the expression of phenolic-compound-related structural genes. The results showed that, during development of the two plums, the total soluble solid and soluble sugar contents were highest at the mature stage. The phenolic contents (total phenol content (TPC), total flavonoid content (TFC), and total flavanol content (TFAC)) trended gradually downward as the fruits of the two cultivars matured, while the total anthocyanin content gradually increased in ‘Cuihongli’. The main phenolic components were neochlorogenic acid, chlorogenic acid, ferulic acid, benzoic acid, rutin, and proanthocyanidin B1. The changes in the DPPH and FRAP scavenging activities decreased with fruit ripening. The antioxidant capacity was positively correlated with the TPC, TFC, and TFAC. In the two cultivars, the total phenols, phenolic components, and antioxidant capacity were higher in the peel than in the pulp. CHS, PAL3, and HCT1 may be the regulatory genes related to the accumulation of phenolic substances in the pericarp and pulp of ‘Qiangcuili’ and ‘Cuihongli’. HCT1 may be an important regulator involved in the accumulation of chlorogenic acid in plums. The changes in the quality of the phenols, phenolic components, and antioxidant activity were elucidated during the development of the main plum cultivars in Sichuan, particularly the changes that provided a theoretical basis for the development of bioactive substances in local plum cultivars.

Sichuan is the China’s leading producer of loquat, with the largest cultivation area and yield ranked first in China. Loquat is a seasonal fruit highly appreciated by consumers; however, the fruit is prone to browning and lignification after harvest, affecting its storage quality. The effects of L-Cysteine (L-Cys, 0.01, 0.05, 0.1, 0.2%) and γ-aminobutyric acid (GABA, 0.025, 0.05, 0.075, 0.1%) on the sensory quality and antioxidant activity of loquat fruit during cold storage at 4 °C for 35 days and simulated shelf life for 5 days were investigated. The results showed that after 40 days of storage, compared with the control, 0.05% L-Cys and 0.05% GABA treatment of ‘Zaozhong No. 6’ loquat fruit effectively reduced the weight loss rate, browning index, decay index, respiratory rate, firmness, and lignin content and slowed the decreases in total soluble solids, soluble sugar, titratable acidityand vitamin C contents. The application of 0.05% L-Cys and 0.05% GABA significantly increased the contents of total phenols, total flavonoids, flavanols, and carotenoids; delayed the increase of relative electric conductivity, MDA, POD, and PPO activities; and significantly enhanced the activities of SOD and CAT, DPPH free radical scavenging ability, and FRAP, thereby improving antioxidant capacity. In summary, 0.05% L-Cys and 0.05% GABA treatment promotes the quality of loquat fruit after 40 days of storage, and significantly enhances antioxidant capacity, thus delaying senescence after harvest.

SHORT VEGETATIVE PHASE (SVP), a member of the MADS-box transcription factor family, has been reported to regulate bud dormancy in deciduous perennial plants. Previously, three LcSVPs (LcSVP1, LcSVP2 and LcSVP3) were identified from litchi genome, and LcSVP2 was highly expressed in the terminal buds of litchi during growth cessation or dormancy stages and down-regulated during growth stages. In this study, the role of LcSVP2 in governing litchi bud dormancy was examined. LcSVP2 was highly expressed in the shoots, especially in the terminal buds at growth cessation stage, whereas low expression was showed in roots, female flowers and seeds. LcSVP2 was found to be located in the nucleus and have transcription inhibitory activity. Overexpression of LcSVP2 in Arabidopsis thaliana resulted in a later flowering phenotype compared to the wild-type control. Silencing LcSVP2 in growing litchi terminal buds delayed re-entry of dormancy, resulting in significantly lower dormancy rate. The treatment also significantly up-regulated litchi FLOWERING LOCUS T2 (LcFT2). Further study indicates that LcSVP2 interacts with an AP2-type transcription factor, SMALL ORGAN SIZE1 (LcSMOS1). Silencing LcSMOS1 promoted budbreak and delayed bud dormancy. Abscisic acid (200 mg/L), which enforced bud dormancy, induced a short-term increase in the expression of LcSVP2 and LcSMOS1. Our study reveals that LcSVP2 may play a crucial role, likely together with LcSMOS1, in dormancy onset of the terminal bud and may also serve as a flowering repressor in evergreen perennial litchi.

Gamma amino butyric acid (GABA), an important free amino acid in plant tissues, plays an essential role in all stages of plant growth and development. In this study, we aimed to explore the effects of GABA on the nutrient absorption of loquat [Eriobotrya japonica (Thunb.) Lindl.] seedlings. The effects of applying exogenous GABA in different concentrations (0.0, 0.5, 1.0, 1.5, and 2 g L⁻¹) on the nutrient uptake of loquat seedlings were studied. GABA increased the biomass (dry weight) and contents of photosynthetic pigments in loquat seedlings to a certain extent. GABA concentration exhibited a quadratic polynomial regression relationship with the biomass. Exogenous GABA in different concentrations increased the total nitrogen (N) and phosphorus (P) contents in loquat seedlings, whereas only 0.5 and 1.0 g L⁻¹ of GABA increased the potassium (K) content. Similarly, GABA concentration also had a polynomial regression relationship with the total N, P, and K contents. Compared to the control, 0.5, 1.0, 1.5, and 2.0 g L⁻¹ of GABA increased the shoot total N content by 27.30, 32.99, 15.41, and 12.93%, respectively, and also increased the shoot total P content by 26.12, 37.52, 21.99, and 9.61%, respectively. Furthermore, correlation and grey relational analyses showed that the carotenoid content, root biomass, and soil alkali-hydrolyzable N concentration were the indicators most closely associated with the uptakes of N, P, and K in shoots. This study shows that exogenous GABA can promote the growth and nutrient uptake of loquat seedlings at an optimum concentration of 1.0 g L⁻¹.

In recent years, high temperature and drought have severely impacted the growth and development of loquat [Eriobotrya japonica (Thunb.) Lindl.] plants. Although dopamine can improve the stress resistance of plants, its role in combined stress requires further exploration. This study investigated the alleviative effect and mechanism of exogenous dopamine on loquat seedlings subjected to the combined stress of high temperature and drought. The combined stress significantly reduced root viability, photosynthetic pigment content, and net photosynthetic rate (Pn) while markedly increasing reactive oxygen species (ROS) levels, thiobarbituric acid-reactive substances (TBARS) content, and electrolyte leakage (EL). The seedlings exhibited pronounced wilting symptoms, along with markedly reduced root surface area and volume. Dopamine treatment significantly alleviated combined stress-induced damage. This mitigation was manifested through substantially enhanced root viability, photosynthetic pigment content, Pn, antioxidant enzyme activities, and osmotic adjustment substances concomitantly with marked reductions in ROS, TBARS content, and EL. Dopamine significantly reduced seedling wilting severity and improved root morphological parameters. This study demonstrates that dopamine enhances loquat seedlings’ tolerance to combined stress through coordinated mechanisms: maintaining photosynthetic pigments and improving stomatal conductance to sustain photosynthetic efficiency, enhancing antioxidant enzyme activity and ROS scavenging capacity to mitigate oxidative damage, and promoting osmotic solute accumulation for osmotic potential regulation.

Flowering represents a critical morphological transition from vegetative to reproductive growth in plants, and optimal timing of this process is essential for loquat (Eriobotrya japonica) production to mitigate natural disasters while improving fruit quality and yield. In this study, comparative phenological and anatomical analyses between autumn-flowering and spring-flowering loquat cultivars revealed that the variation in flowering time primarily stems from differences in both the initiation of floral bud differentiation and the development of inflorescence lateral axes. Morphological differentiation timing was identified as the predominant factor influencing flowering period divergence. Transcriptome profiling of floral development in autumn-flowering ('Guozhenhao 3') and spring-flowering ('Chunhua No.1') loquat cultivars revealed that the late morphological development stage exhibited the highest number of differentially expressed genes, which were significantly enriched in pathways related to floral organ development, whorl formation, and gibberellin (GA) signal transduction. Weighted Gene Co-expression Network Analysis (WGCNA) of differentially expressed genes (DEGs), hormones, and flowering time identified four DELLA genes repressed by gibberellin signaling. The two loquat cultivars exhibited distinct endogenous gibberellin dynamics during floral bud differentiation. Exogenous GA₃ application during early morphological differentiation in two loquat cultivars promoted floral development and early flowering through coordinated regulation of GA biosynthesis genes (C19-GA2OX1, C20-GA2OX1, GA3OX, GA20OX), the GA signaling repressor DELLA (EjRGL3a), and flowering integrators (EjAGL24, EjLFY). EjRGL3a silencing during early bud differentiation accelerated flowering and upregulated floral integrators (EjAP1, EjLFY, EjAGL24) in two loquat cultivars. These findings provide mechanistic insights into the regulatory role of gibberellin in loquat flowering.