Screening Citrus Cultivars for Freezing Tolerance by Reliable Methods
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.