Measurements of freezing tolerance and their relationship with some biochemical and physiological parameters in seven olive cultivars

Abstract

The freezing tolerance of seven olive cultivars, including Amphisis, Conservallia, Koroneiki, Manzanilla, Gorgan, Shengeh, and Rashid, was compared, and its correlation with some biochemical and physiological factors was investigated. From each cultivar, leaf and stem samples were collected and sorted into two groups: the first was exposed to various freezing temperatures to indicate its freezing tolerance in terms of lethal temperature (LT50) values by several approaches (electrolyte leakage, maximum quantum yield of PSII photochemistry, and tetrazolium staining test); the second was prepared for some biochemical and physiological parameter analyses. Of all cultivars, Amphisis and Shengeh showed the highest freezing tolerance, the maximum soluble carbohydrate and proline content, DPPH (1, 1-diphenyl–2-picrylhydrazyl) scavenging capacity, the minimum malondialdehyde (MDA), and relative water content (RWC). Conservallia, Gorgan, and Manzanilla cultivars could moderately tolerate freezing temperatures, whereas Rashid and Koroneiki cultivars turned out to be freezing-susceptible. In olive bark and leaf, LT50 showed a negative correlation with soluble carbohydrate, proline content, and DPPH scavenging capacity and a positive correlation with MDA and RWC. Three indicators, i.e., LT50, osmoregulant content, and DPPH scavenging capacity, can contribute to screening the freezing-tolerant olive cultivars.