Chenbing Wang

During the dormant period of peach trees in winter, flower buds exhibit weak cold resistance and are susceptible to freezing at low temperatures. Understanding the physiological and molecular mechanisms underlying the response of local peach buds to low-temperature adversity is crucial for ensuring normal flowering, fruiting, and yield. In this study, the experimental materials included the conventional cultivar ‘Xia cui’ (XC) and the cold-resistant local resources ‘Ding jiaba’ (DJB) peach buds. The antioxidant enzyme activity, levels of malondialdehyde (MDA), proline (Pro), and hydrogen peroxide content (H₂O₂) were determined in peach buds at different dormancy periods. Transcriptome sequencing was performed at three dormancy stages: the dormancy entry stage (FD), deep dormancy release stage (MD), and dormancy release stage (RD). Additionally, transcriptome sequencing was conducted to analyze gene expression profiles during these stages. Our findings revealed that compared with XC cultivars, DJB peach buds exhibited decreased MDA and H₂O₂ contents but increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities as well as Pro content during the dormancy period. These findings suggest that cold-resistant cultivars possess significantly stronger antioxidant capacity than conventional cultivars under low-temperature stress. A total of 10,168 differential genes were annotated through transcriptome sequencing. Among them, 4975 were up-regulated while 5193 were down-regulated. The differentially expressed genes associated with low-temperature response in peach buds are primarily enriched in plant hormone signal transduction pathway and phenylpropane synthesis pathway. Key differentially expressed genes related to cold resistance include ARF2, GH3, and SAPK2, and differentially expressed transcription factors mainly belong to the AP2/ERF-ERF, bHLH, and C2H2 families. This study provides a theoretical foundation for understanding the key genes involved.

Peach bud differentiation is commercially significant for fruit production. Bud differentiation in peach production is closely linked to chilling requirements. This study investigates the mechanisms of flower bud differentiation in peach varieties L12 and N1 under varying chilling requirements by comparing paraffin sections, hormone content changes, and transcriptomes during four chilling hours and the same physiological stage. At 400 chilling hours, significant changes in flower bud differentiation were observed. During this period, the hormone levels of auxin and gibberellin reached their peak, while abscisic acid levels were at their lowest. This finding indicates that 400 chilling hours has a significant regulatory effect on flower bud development. Transcriptome analysis revealed that 4719 differentially expressed genes were identified in the flower bud differentiation of L12-4 and N1-4, and 2717 differentially expressed genes of L12-8 and N1-2, many of which are involved in IAA, GA, and ABA signal transduction pathways. In N1, the differentially expressed genes AUX/IAA, SAUR, and DELLA were significantly higher than in L12, whereas genes associated with the ABA synthesis pathway, such as PYL2, PYL8, and SRK2A, remained at the lowest level. This study provides a crucial molecular basis for understanding the regulation of plant hormones and their effects on flower bud development under varying chilling hours.

In recent years, extreme weather events have become increasingly frequent, and low winter temperatures have had a significant impact on peach cultivation. The selection of cold-resistant peach varieties is an effective solution to mitigate freezing damage. To comprehensively and accurately evaluate the cold resistance of peaches and screen for high cold resistance among Gansu local resources, nine different types of peach were selected as test resources to assess physiological, biochemical, and anatomical indices. Subsequently, 28 peach germplasms were evaluated using relevant indices. The semi-lethal temperature (LT50) was calculated by fitting the change curve of the electrolyte leakage index (ELI) with the Logistic equation; this can be used as an important index for identifying and evaluating the cold resistance of peach trees. The LT50 values ranged from −28.22 °C to −17.22 °C among the 28 tested resources; Dingjiaba Liguang Tao exhibited the lowest LT50 value at −28.22 °C, indicating its high level of cold resistance. The LT50 was positively correlated with the ELI and malondialdehyde (MDA) content with correlation coefficients of 0.894 and 0.863, respectively, while it was negatively correlated with the soluble sugar (SS), soluble protein (SP), and free proline (Pro) contents with correlation coefficients of −0.894, −0.721, and −0.863, respectively. The thicknesses of the xylem, cork layer, cork layer ratio (CLR) and thickness/cortex thickness (X/C) showed negative correlations (−0.694, −0.741, −0.822, −0.814, respectively). Finally, the membership function method was used to evaluate cold resistance based on the ELI, MDA, Pro, SP, SS, CLR, and xylem thickness/cortex thickness (X/C) indices. The average membership degree among all tested resources ranged from 0.17 to 0.61. Dingjiaba Liguang Tao emerged prominently in terms of high-cold-resistance (HR) membership value (0.61).