Abstract
Assessing pollen viability and anomalies is essential to optimize resources and improve hazelnut productivity. However, knowledge of pollen viability dynamics across cultivars and environments remains limited. This study applied impedance flow cytometry to (i) monitor pollen hydration and define optimal rehydration time, (ii) quantify pollen viability over three flowering seasons, and (iii) evaluate genetic, environmental, and agronomic influences on viable and anomalous pollen formation. Viable pollen showed an adaptive response, restoring high viability (~85%) after four hours of hydration following dehydration stress. Viability displayed cultivar-specific patterns, stable across years but variable among sites. In Viterbo (central Italy, Mediterranean climate), flowering occurred 2-4 weeks earlier than in northern orchards (Piedmont, continental climate). Wild-type accessions exhibited higher viability and minimal anomalous pollen (<3%), whereas cultivated genotypes maintained abundant anomalous pollen (30-50%) across sites and seasons. Multifactorial analysis revealed that both genotype and environment affected viable pollen, while anomalous pollen depended mainly on genotype. Overall, pollen viability results from the interaction between genetic predisposition and local conditions, whereas anomalous pollen reflects stable, genotype-linked traits. These findings highlight the dominant role of cultivar-specific genetics in hazelnut pollen quality, providing a framework for breeding and orchard management strategies.