Abstract
The seasonal availability of airborne ascospores of Venturia inaequalis is a key determinant of primary apple scab infections, and mechanistic models describing ascospore maturation are widely used in disease forecasting systems. However, the applicability of such models under climatic conditions different from those for which they were originally developed remains insufficiently evaluated. This study presents a field evaluation of the climatic transferability of the Proportion of Ascospores capable of becoming Airborne (PAT) based ascospore maturation model proposed by Rossi et al. in 2000, under the temperate Himalayan conditions of Jammu and Kashmir, India. The original model structure and equations were retained and applied using hourly meteorological data (air temperature, rainfall, relative humidity and leaf wetness) collected over six consecutive seasons (2020–2025). Model outputs describing ascospore maturation and discharge dynamics were evaluated against independent field observations of airborne V. inaequalis ascospores obtained using a volumetric spore trap. Validation was conducted using event-based biological validation and statistical goodness-of-fit metrics. The model consistently reproduced the timing of ascospore availability, the accelerated maturation phase, and the exhaustion of the primary ascospore pool. Approximately 90% of observed ascospore release events occurred within model-predicted release-favourable windows. Statistical evaluation of maturation trajectories showed excellent agreement between predicted and observed dynamics (R2 ≈ 0.99; CCC = 0.96 -1.00). These results demonstrate that the PAT-based ascospore maturation model retains its predictive capability under temperate Himalayan conditions with little parameter calibration and is suitable for supporting regionally adapted apple scab disease warning systems.
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Acknowledgements
The authors acknowledge the Division of Agrometeorology, SKUAST-K, for providing meteorological support and access to weather observations used during the study. The authors also acknowledge Meteoblue weather services and the India Meteorological Department (IMD) for providing supplementary meteorological data used for cross-validation and verification of weather observations.
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The authors declare that no funding, grants, or other financial support was received for the conduct of this study or the preparation of this manuscript.
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Bashir, A., Mir, S.A., Rasool, T. et al. Climatic transferability and regional validation of a PAT-based mechanistic model for apple scab ascospore maturation under temperate Himalayan conditions.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-55192-7
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DOI: https://doi.org/10.1038/s41598-026-55192-7
Keywords
- Model development
- Apple scab
Venturia inaequalis
- Ascospore release
- Spore maturation
- Temperate Himalayas
- Epidemiology
Source: Ecology - nature.com
