Physiological responses and evaluation of cold tolerance in red prickly ash (Zanthoxylum bungeanum Maxim.) germplasm under low-temperature treatment

This study investigated how red prickly ash germplasms respond physiologically to low-temperature treatments. Sixteen red prickly ash germplasms were utilized to examine variations in physiological indices at 0, −10, −20, and −30 °C. The results showed that low-temperature treatment led to an increase in the relative conductivity (REC) of the germplasms. The semi-lethal temperatures of germplasms WCDHP, CCSJ, and HGHJ were lower than −10 °C, while those of germplasms JYH, NLJ, and CJ were higher than −7 °C. With decreasing temperature, the levels of soluble sugar (SS) and soluble protein (SP) initially declined, subsequently increased, and finally decreased, while the concentration of free proline (PRO) initially increased and then decreased. In addition, with decreasing temperature, the activity of superoxide dismutase (SOD) increased and then decreased, whereas those of peroxidase (POD) and catalase (CAT) increased, then decreased, and then increased. HGHJ, CCSJ, and SZT had the highest comprehensive membership function scores, whereas CJ, JQWC, and NLJ had the lowest comprehensive scores. Eight germplasm lines (including CCSJ, PTJ, and HGHJ) screened using principal component analysis (PCA) showed strong cold tolerance, whereas BYH, TSWC, and CJ exhibited weak cold tolerance. In summary, CCSJ and HGHJ demonstrated strong cold tolerance, whereas NLJ and CJ demonstrated weak cold tolerance.