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.

The study aimed to evaluate the cold tolerance of various peach cultivars under diverse low-temperature conditions (−5, −10, −15, −20, −25, −30, and −35 °C). A comprehensive assessment of their responses to cold was performed by integrating LT50 values with membership functions and evaluating local adaptability among the selected peach cultivars. The findings revealed that as temperatures dropped, electrical conductivity (REC), malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) levels initially rose, then fell, and subsequently increased once more. Soluble sugar (SS) and soluble protein (SP) concentrations peaked at −25 °C and showed a significant negative correlation with semi-lethal temperature (LT50). The expression of free proline varied among different samples. Combining physiological analyses with field adaptation correlation assessments, it was found that ‘Ziyan Ruiyang’ exhibited a relatively low LT50 value of −29.67 °C and a membership function degree of 0.76, suggesting robust field adaptation abilities. At the same time, ‘Ganlu Shumi’ demonstrated stable trends in H₂O₂ and MDA levels, maintaining them at relatively low concentrations; it also had the lowest LT50 value, the highest membership function score, and the highest survival rate. Consequently, this cultivar could be a valuable resource for enhancing cold resistance under low-temperature stress. In summary, by correlating LT50 values with membership functions and observing local adaptability in these peach cultivars, we have established reliable data that can serve as a basis for identifying potential cross-breeding parents to develop new cold-resistant varieties.

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.

Late frost damage in spring is a significant limiting factor in peach industry development, with the flowering period being the most vulnerable to late frost. This study aimed to observe the flower organ state and physiological changes of two peach varieties under various temperature treatments and to provide a theoretical basis for selecting frost-resistant varieties. By analyzing the supercooling points of ‘Longyoutao 1’ (Y1) and ‘Longmi 15’ (L15), we simulated late frost at five temperatures, 4 °C, 2 °C, 0 °C, −2 °C, and −4 °C, and observed the flower organ changes at these five temperature stages during the flowering period. The contents of flower hormones (IAA, GA, ABA), membrane lipid peroxidation products (MDA), antioxidant enzymes (POD, SOD, CAT), and osmoregulatory substances (Pro, SS) were analyzed under various low-temperature stress conditions. The results showed no significant difference in flower morphology between Y1 and L15 at 4 °C, 2 °C, and 0 °C. At −2 °C, the anthers of Y1 turned brown and dried, the ovary froze, and water stains appeared on the sepals and the center. At −4 °C, the water stain on the ovary intensified, and the ovule froze. Moreover, by integrating the differences in the contents of IAA, GA, ABA, MDA, POD, SOD, and SS of the two varieties at the critical temperature of 0 °C, L15 showed the strongest ability to resist late frost. This study provides a physiological foundation for researching frost resistance during the flowering period.