Forty-year investigations on apricot blooming: Evidences of climate change effects

Current climate change negatively impacts on key seasonal biological processes of perennial plants causing erratic productions and, consequently, significant yield reductions. Being flowering time of fruit crops one of the most widely used indicators for climate change studies, the present research aimed to assess, over a long-term period (1973-2016), the climatic trend and its influence on blooming date and intensity of 40 apricot cultivars (Pnuius armeniaca L.) grown in central Italy. Over the autumn-spring seasons, the main climatic parameters (temperature, rainfall) were acquired, and calculation of chill accumulation according to the Chilling Units model (CU) was performed. Results showed significant trends in warming of autumn-winter monthly minimum and average temperatures, particularly since the 1990s. During the critical period for overcoming of flower bud endodormancy, a dramatic loss of CUs was recorded. Most of the examined cultivars, belonging to Italian and foreign germplasm and opportunely selected for different flowering time, showed important blooming delays and blooming intensity decreases. In particular, the early-blooming cultivars showed the highest average shift of around 12 days and a loss in blooming intensity score which fell to levels of around 50% with respect to previous periods. The CUs, negatively correlated with blooming time and positively correlated with blooming intensity, seem to be crucial for apricot floral biology. The irregular autumn-winter cold rate of recent years may mean that substantial impacts can be expected in the future with possible geographic shifts of the apricot cultivation areas towards more potentially suitable areas located in the northern Italian and European regions, with considerable socioeconomic inference.