Physio-Biochemical Insights into the Cold Resistance Variations among Nectarine ( Prunus persica (L.) Batsch var. nectarina ) Cultivars.

Cold stress occurs in late winter and early spring threatens greatly the nectarine industry. In this study, the semi-lethal low temperature (LT 50 ) and thirteen cold resistance related parameters of five nectarine cultivars, including 'Nonglehong little princess' (LP), 'Luyou No. 5' (LY), 'Nonglehong No. 6' (NL), 'Zhongyou No. 20' (ZY) and 'Qiuhongzhu' (QH), were determined. Based on these parameters, they were categorized into high-(HR, including NL and LP), moderate-(MR, including QH) and low-cold resistant (LR, including ZY and LY) groups. The relative water (RW), proline (PRO), soluble sucrose (SS) and soluble protein (SP) contents, and superoxide dismutase (SOD) and peroxidase (POD) activities of HR cultivars were higher while their relative electronic conductivity (RE), malondialdehyde (MDA) and gibberellin acid (GA 3 ) contents and catalase (CAT) activity were lower than other cultivars during natural overwintering. Redundancy analysis revealed that the lowest temperature in a day (LT) and LT 50 significantly explains 69.8% and 10.9% of these physiological variables, respectively. Moreover, GA 3 and indoleacetic acid (IAA) contents and CAT activity were positively correlated, while PRO, SS, ABA and RW contents were negatively correlated with both LT and LT 50 . Our study will be helpful in understanding the cold resistance variations of nectarine germplasm resources.