The fulfilment of chilling requirements and the adaptation of apricot (Prunus armeniaca L.) in warm winter climates: An approach in Murcia (Spain) and the Western Cape (South Africa)

Different chilling requirements (CRs) are required for apricot (Prunus armeniaca L.) cultivars to overcome dormancy. In a global climate change context, knowledge of these requirements is critical; producers must select the appropriate cultivars to avoid losses caused by an inadequate cultivar adaptation in a particular area. Important differences have been reported in the CRs of cultivars of temperate fruit crops that are cultivated in different climatic conditions. However, the lack of standardisation of protocols to calculate CRs hinders the comparison of the results obtained using different methodologies. This study was aimed at analysing adaptation in terms of the CR fulfilment of commercial apricot cultivars grown successfully in different climatic conditions. Apricot-growing locations with different latitudes and altitudes and cultivars with varying CRs were chosen. The plant material spanned the CR range for this species in South Africa and Spain. Three of the examined cultivars were tested simultaneously in both countries. The Utah, Dynamic and hours below 7 degrees C models for estimating CR were evaluated and compared. The cultivars examined displayed different CR ranges in Spain and South Africa. We concluded that CR differences higher than 50% can be found for clonal plant material grown successfully in different climatic conditions. This variation might be associated both with different temperatures and other factors such as latitude. No significant differences in heat requirements were found among cultivars in Spain, suggesting that this variable might not be cultivar-specific. Finally, the distribution of clonal plant material provides an excellent framework for studying the climatic adaptation of crops. (C) 2011 Elsevier B.V. All rights reserved.