Objective To investigate the evaluation method of cold resistance of olive cuttings.

MethodsEight two-year cuttage seedlings of olive varieties were introduced and planted in the valley of Bailong River on the southern slope of West Qinling Mountains in North subtropical China. Cold stress (16, 12, 8, 4, 0, −4 ℃) was simulated to measure the contents of osmotic regulation substances, protective enzyme activities, photosynthesis and chlorophyll fluorescence parameters.

ResultsWith the increase of cold stress, the contents of relative electrical conductivity (REC), proline (Pro), soluble sugar (SS) and soluble protein (SP) in the leaves of 8 tested olive varieties showed an increasing trend, and the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased before 0 ℃ and then began to gradually decreased after freezing point; During the process of temperature decrease, leaf chlorophyll content (Chl), net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (T_r), maximum photochemical efficiency (F_v/F_m) and actual photochemical efficiency (ΦPSⅡ) of all varieties showed a decreasing trend,stomatal conductance (G_s) showed a decreasing trend before -4℃. Correlation analysis was conducted using three evaluation systems: semi-lethal temperature (LT₅₀), membership functions of osmotic regulatory substances and protective enzymes, and membership functions of photosynthesis and chlorophyll fluorescence. The results showed that the semi-lethal temperature of eight olive varieties ranged from -16.359 ℃ to -9.715 ℃.

Conclusion The comprehensive ranking of cold resistance obtained by the method of subordinate function of the activity parameters of osmotic regulatory substances and protective enzymes is basically consistent with the ranking of semi-lethal temperature obtained by the method of conductivity and Logistic equation, and is consistent with the overwintering performance of olive in the test area. It can be used as an evaluation method for cold resistance of olive at seedling stage.