Sequences of the primers.

Blueberry is a small berry with significant economic value; however, in the northern regions of China, low temperatures severely affect blueberry growth during early spring. Salicylic acid (SA), an important phytohormone, plays a crucial role in various physiological and metabolic responses induced by abiotic stress. This study utilized 2-year-old ‘Northland’ blueberry plants as experimental materials to investigate the physiological responses to different concentrations of SA supplementation under low-temperature stress. The results indicated that SA concentration had varying effects on enhancing the cold resistance of blueberry plants under different low-temperature conditions. At a stress temperature of 4°C, a concentration of 2.5 mM SA was most effective in increasing the content of osmoregulatory substances, enhancing the activity of antioxidant system enzymes, reducing reactive oxygen species (ROS) accumulation, up-regulating the ascorbate-glutathione (AsA-GSH) cycle, and elevating the expression level of the VcICE1 compared to other concentrations. Conversely, under low-temperature stress below 0°C (including 0°C and −4°C), supplementation with 0.5 mM SA resulted in the most significant improvement compared to the control. Therefore, the study findings suggest that the application of 0.5 mM SA enhances the cold tolerance of blueberries. However, additional validation is required to ascertain its efficacy when applied in early spring fields in northern China.