Model-based analysis of chill accumulation in European hazelnut catkins highlights site-specific climatic sensitivity across Italian locations
Author(s)
Date Issued
September 2026
Type
article
Volume
180
ISSN
1161-0301
Journal
Abstract
Rising global demand for hazelnuts requires improved tools to support cultivar adaptation without compromising
quality. This study evaluated male flowering phenology and chilling accumulation over three years in
four European hazelnut cultivars and one wild type accession grown in two contrasting environments: Viterbo
(central Italy, sub-coastal temperate climate) and Chieri (northern Italy, sub-continental temperate climate).
Pollen dispersal was monitored, and chilling accumulation was calculated from November 1st to dormancy
release using chilling hours (CH, 0–7 ◦C), Utah (chilling units, CU), and Dynamic (chilling portions, CP) models.
Results revealed clear genotype-specific differences in flowering timing and duration. Early-flowering cultivars
reached anthesis two to four weeks earlier in Viterbo than in Chieri, reflecting adaptation to local mesoclimatic
conditions. Chilling accumulation differed significantly between sites, with consistently lower values in the
warmer environment. Among models, CH showed the most stable and consistent response to environmental
differences and best agreement with observed phenology, while CU provided comparable but slightly less robust
estimates. CP captured the influence of temperature fluctuations and warm spells, but showed less consistency in
cross-site comparisons. These findings highlight the strong interaction between genotype and environment in
hazelnut phenology and emphasize the importance of selecting appropriate chilling models to support cultivar
choice and orchard management under variable climatic conditions
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Name
Article pollen chilling hazel EJA 2026.pdf
Size
4 MB
Format
Adobe PDF
Checksum (MD5)
6866952751ca29cca4f0f3d91b0f4c69
Project(s)
(1) FERRERO TRADING LUX S.A.— project “Characterizing male and female sterility in hazelnut cultivars” and (2) by ARSIAL (Regional Agency for Innovation and Development of Agriculture in Latium, Project DD n. 296 of 08/05/2023).