Pollen limitation and a phenological climate inversion drive olive yield instability in North-East Italy
Abstract
The northward expansion of olive (Olea europaea L.) cultivation into marginal areas such as the Veneto region (northern Italy) exposes the crop to climatic and reproductive constraints that may enhance alternate bearing. To identify the primary drivers of this yield instability, we combined a decadal regional macro-climatic analysis with a localized field experiment. Regional time-series data (2015–2025) for production, airborne pollen and fruit set were related to temperature and precipitation anomalies, revealing airborne pollen load as the strongest predictor of annual production (R² = 0.76, p < 0.001). The analysis also identified a phenological “climate trap”: warmth and dryness favored pre-flowering and early flowering (April–mid-May) processes, whereas early-summer heat and water deficit triggered severe abscission during late flowering and fruit set (late May–June). Meteorological conditions during a two-year (2025–2026) field trial on cv. Arbequina closely mirrored this climate trap, offering a preliminary test of its consequences. Supplementary mechanical pollination sharply reduced fruit abscission compared to natural wind pollination, likely via improved fertilization rather than stress buffering, raising fruit set from 0.9% to 4.2% in 2025 and from 0.6% to 3.2% in 2026, and decreasing fruitless shoots (seven inflorescences each) from 63.3% to 23.3% and from 70.0% to 17.8%, respectively. Pollinated fruits were also more uniform in size in both years. These results suggest that pollen availability, not heat or drought per se, may constrain fruit set at this climatic margin, supporting compatible pollinizers as the structural remedy and mechanical pollination as an emergency alternative.
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BibTeX
@article{carraro2026pollen,
title = {{Pollen limitation and a phenological climate inversion drive olive yield instability in North-East Italy}},
author = {Pietro Carraro and Diego Mina and Francesco Tarateo and Gianni Tacconi and Michele Giannini and Zeno Varanini and Anita Zamboni and Claudio Bonghi and Benedetto Ruperti},
journal = {Frontiers in Plant Science},
year = {2026},
month = nov,
doi = {10.3389/fpls.2026.1994811},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1994811},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Pollen limitation and a phenological climate inversion drive olive yield instability in North-East Italy
AU - Pietro Carraro
AU - Diego Mina
AU - Francesco Tarateo
AU - Gianni Tacconi
AU - Michele Giannini
AU - Zeno Varanini
AU - Anita Zamboni
AU - Claudio Bonghi
AU - Benedetto Ruperti
PY - 2026
DA - 2026/11/06
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1994811
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1994811
AB - The northward expansion of olive (Olea europaea L.) cultivation into marginal areas such as the Veneto region (northern Italy) exposes the crop to climatic and reproductive constraints that may enhance alternate bearing. To identify the primary drivers of this yield instability, we combined a decadal regional macro-climatic analysis with a localized field experiment. Regional time-series data (2015–2025) for production, airborne pollen and fruit set were related to temperature and precipitation anomalies, revealing airborne pollen load as the strongest predictor of annual production (R² = 0.76, p < 0.001). The analysis also identified a phenological “climate trap”: warmth and dryness favored pre-flowering and early flowering (April–mid-May) processes, whereas early-summer heat and water deficit triggered severe abscission during late flowering and fruit set (late May–June). Meteorological conditions during a two-year (2025–2026) field trial on cv. Arbequina closely mirrored this climate trap, offering a preliminary test of its consequences. Supplementary mechanical pollination sharply reduced fruit abscission compared to natural wind pollination, likely via improved fertilization rather than stress buffering, raising fruit set from 0.9% to 4.2% in 2025 and from 0.6% to 3.2% in 2026, and decreasing fruitless shoots (seven inflorescences each) from 63.3% to 23.3% and from 70.0% to 17.8%, respectively. Pollinated fruits were also more uniform in size in both years. These results suggest that pollen availability, not heat or drought per se, may constrain fruit set at this climatic margin, supporting compatible pollinizers as the structural remedy and mechanical pollination as an emergency alternative.
SN - 1664-462X
ER -