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.

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.

Low temperature is the main abiotic stress affecting the growth and development of plants in the cold region of northwest China. Gansu local varieties are