Exploitation of genotypic variation in chilling and heat requirements for flowering in Prunus armeniaca and Prunus persica (L.) Batsch cultivars

Abstract

In a rapidly changing climate resulting in warmer winters, knowledge on the chilling and heat requirements of deciduous fruit tree cultivars is a pre-requisite for adaptation; however little is known on commercially available P. armeniaca (apricot) and P. persica (L.) Batsh (peach/nectarine) cultivars. We quantified the chilling and heat requirements of 50 apricot, and 49 peach/nectarine cultivars commercially grown, evaluated the consistency of results over different years, and relationships with bloom dates. The range of chilling requirements was similar in the apricot and the peach/nectarine cultivars studied (43–73 Chilling Portions, 807–1473 Chill Units), yet a greater portion of apricot and non-melting peach cultivars were categorized under the high chilling requirement group. Apricot cultivars had a later day of breaking dormancy, but similar full bloom day compared with the peach/nectarine cultivars, which are related to having lower heat requirements for flowering (mean 3783 vs. 5100 Growing Degree Hours, respectively). Only few apricot (‘Anegat’ and ‘Pluot’) and peach/nectarine (‘Carla’, ‘Tastired’, ‘Royal Queen’, ‘Crimson Lady’ and ‘Ferlate’) cultivars attain combination of low or medium chilling requirements, and high heat requirements, linked with better resilience to warm winters, and ensuring late bloom time to avoid frost damages. Measured values of chilling requirements were higher in the high− chill year, in apricot, but not in peach/nectarine cultivars. The chill accumulation during the 2016–2022 experimental autumn/winter periods ranged from 72 to 86 Chilling Portions. Under the current climate conditions in Naoussa, and considering recent predictions, chilling accumulation will be insufficient for the ‘High’ chill cultivars of both species, therefore choosing the appropriate cultivars and breeding efforts are required for adaptation.