Production area and climate as predisposing factors in the development of chilling injury of citrus fruit

South Africa produces citrus in a diverse range of geographical areas and climatic conditions. These include the cold costal production regions of the Eastern Cape where the highest rainfall occurs in both spring and autumn, the hot dry and intermediate north-eastern parts of South Africa where summer rainfall and dry winters dominate, and the Western Cape as a winter rainfall region (cold coastal and Mediterranean climate). The effect of growing regions on the growth and yield of trees and the internal and external quality of fruit is known. However, the effects on the susceptibility of fruit to postharvest physiological rind disorders are unknown. This study aimed to disentangle the effects of production region and the associated climate on a predisposition of fruit to postharvest chilling injury (CI) during cold shipment and storage. This study was carried out over two seasons in four areas representing the main production regions of South Africa: Citrusdal in the Western Cape, Sundays River Valley (SRV) in the Eastern Cape, Letsitele in Limpopo and Nelspruit in Mpumalanga. Five cultivars were identified as being representative of the various citrus groups i.e., ‘Nova’ mandarin (Western and Eastern Cape only) and ‘Nadorcott’ mandarin, ‘Star Ruby’ grapefruit (Limpopo and Mpumalanga only), ‘Turkey’ and ‘Midknight’ Valencia. Results show differences between production areas and seasons on the impact on CI susceptibility of fruit. Climate was found to have significant effects on both fruit quality and CI, even though seasonal differences in the incidence occurred. Whilst there were differences in incidence and severity between cultivars, the cold coastal summer rainfall area had the highest overall CI. Results from this novel approach are part of efforts to improve the handling protocols of cultivars from different production regions.