Phenological diversity in a World Olive Germplasm Bank: Potential use for breeding programs and climate change studies

Aim of study: Crop phenology is a critical component in the identification of impacts of climate change. Then, the assessment of germplasm collections provides relevant information for cultivar selection and breeding related to phenology, being the base for identifying adaptation strategies to climate change.Area of study: The World Olive Germplasm Bank located at IFAPA Centre “Alameda del Obispo” (WOGB-IFAPA) in Cordoba (Southern Spain) was considered for the study.Material and methods: Data gathered for nine years on flowering and ripening time of olive cultivars from WOGB-IFAPA were evaluated. Thus, full flowering date (FFD) for 148 cultivars and ripening date (RD) for 86 cultivars, coming from 14 olive growing countries, were considered for characterization of olive phenology and for calibration/validation of phenological models.Main results: The characterization of WOGB-IFAPA has allowed the identification of cultivars with extreme early (‘Borriolenca’) and late (‘Ulliri i Kuq’) flowering as well as the ones with extreme early (‘Mavreya’) and late (‘Gerboui’) ripening dates. However, the very limited inter-cultivar variability, especially for FFD, resulted in a non-optimal simulation models performance. Thus, for FFD and RD the root mean square error was around 6 and 24 days, respectively. The limited inter-cultivar variability was associated to the low average temperatures registered during winter at WOGB-IFAPA generating an early accumulation of the chilling requirements, thus homogenizing FFD of all the analyzed cultivars.Research highlights: The identification of cultivars with early FFD and late RD provides useful information for breeding programs and climate change studies for identifying adaptation strategies.