Document Type : Research paper

Authors

• Ali Salehi Sardoei ¹
• Mehdi Sharifani ¹
• Mostafa Khoshhal Sarmast ¹
• Mahmoud Ghasemnejad ²

¹ Department of Horticultural Science, Faculty of Plant Production, Gorgan University of Agriculture and Natural Resources, Gorgan, Iran

² Department of Horticultural Science, Faculty of Agriculture, University of Guilan, Guilan, Iran

Abstract

Citrus species are comprised of susceptible plants that can barely tolerate freezing temperatures. To determine the relationship between cold stress tolerance (LT50) and some important physiological traits, four commercial citrus cultivars of citrus species were studied. These were Citrus unshiu, Citrus sinensis var. ‘Thomson navel’, Citrus paradisi var. ‘Star Ru by’ and Citrus limon var. ‘Lisbon’. Assessments of cold-stress tolerance were carried out at 4, -4 and -8 °C. Ultimately, the results showed that the Japanese mandarin and ‘Thomson navel’ had the highest stress tolerance (LT50). Citrus unshiu tolerated cold stress up to -8.4 LT50. The correlation coefficient demonstrated that significant, positive correlations were observed between several pairs of attributes, i.e. LT50 and total flavonoids, chlorophyll a and chlorophyll b, carotenoids and chlorophyll a, chlorophyll b and total chlorophyll, relative moisture content and malondialdehyde, as well as glycine betaine and catalase. According to the regression coefficient, a change of one unit in lipid peroxidation caused a decrease of 1.9238 units and 5.9615 units in LT50 at +4 and -4 °C, respectively. While commercial citrus cultivars were selected for cold-tolerance and other traits, the efficiency of cold-tolerance correlated more with carotenoid content, chlorophyll content and lipid peroxidation, considering the assessments at particular temperatures.

Keywords

• Plant breeding
• Principal component analysis
• Regression
• Low temperatures