Comparison of chilling requirements among pomegranate cultivars

Pomegranate (Punica granatum L.) is a deciduous fruit tree species that requires a certain amount of winter chilling to enter and overcome the period of dormancy. Pomegranate cultivars exhibit variable chilling and heat requirements for dormancy release, budbreak, and flowering. Understanding these thermal requirements is essential for both agronomic management and the selection of suitable cultivars for specific regions to prevent potential economic losses due to inappropriate cultivar choice. To date, limited information is available on the chilling/heat requirements of several pomegranate cultivars. In the 2024–2025 winter season, the chilling and heat requirements of four pomegranate cultivars were evaluated: two international (Wonderful and Fleischman’s) and two of Puglia origin and distribution (Dente Molfetta and Acido Torrelonga). Chilling requirements were estimated under controlled temperature in the laboratory using the Weinberger model (∑ hours ≤ 7.2 °C), while heat requirements were calculated in Growing Degree Hours (GDH) according to the linear Richardson model. The number of chilling hours required for dormancy release varied significantly among cultivars, ranging from 100 to 500 hours ( < 7.2 °C), while heat requirements for budbreak ranged from 1624 to 4408 GDH. The cultivar with the lowest chilling requirement under controlled conditions was Fleischman’s (100 hours), followed by Acido Torrelonga (200 hours), and both Dente Molfetta and Wonderful (300–400 hours). Different chilling treatments significantly influenced budbreak rates: the 400- and 300-hour chilling treatments yielded the highest budbreak percentages (23.4% and 16.43%, respectively), while the control (no chilling) and 600-hour treatments resulted in lower values (4.1% and 5.6%, respectively). Fleischman’s responded positively to all six chilling treatments, unlike Wonderful, Dente Molfetta, and Acido Torrelonga. These findings contribute to a better understanding of the thermal requirements of pomegranate and provide useful insights into the behaviour of different cultivars, which may be of interest for future cultivation in the Puglia region and other areas with similar climatic conditions.