Vapor pressure deficit normalizes diurnal photochemical reflectance index for repeatable drought phenotyping of Prunus rootstocks in Mediterranean climates
4 affiliations
- 1Centro de Estudios Avanzados en Fruticultura (CEAF)
- 2Instituto de Investigaciones Agropecuarias (INIA), Rayentué
- 3Laboratory of Fruit Pathology, Facultad de Ciencias Agrarias, Universidad de Talca
- 4Plant Breeding and Phenomics Center, Facultad de Ciencias Agrarias, Universidad de Talca
Abstract
Breeding programs need field-ready traits to compare rootstock drought performance under fluctuating atmospheric demand, particularly in Mediterranean climates where vapor pressure deficit (VPD) can increase abruptly during the day and confound midday “snapshot” screening. We present a VPD-based method to normalize and decompose diurnal dynamics of the photochemical reflectance index (PRI) into repeatable components. Six Prunus rootstocks genotypes were grown under well-watered (WW) and water-deficit (WD; 40% of field capacity) conditions. Leaf PRI was measured hourly (10:00–18:00) on three days spanning VPDmax ≈ 4.9–3.3 kPa, while midday gas exchange and leaf water potential were measured on two days. PRI relationships with incident radiation were weak and variable across genotypes and dates, whereas PRI–VPD trajectories were structured and consistently separated WW and WD conditions. For each genotype, date, and water-regime, PRI–VPD regressions were fitted and decomposed into (i) basal PRI at a common reference VPD (VPDref = 2.0 kPa), (ii) the diurnal PRI–VPD slope, and (iii) WW–WD separation at VPDref. Basal PRI and WW–WD separation produced stable genotype rankings across days (Spearman ρ ≈ 0.8–0.9). Across genotypes, water-deficit–induced changes in PRI (WD relative to WW) tracked changes in stomatal conductance (gs) and transpiration (E). This VPD-normalized decomposition provides a scalable optical trait to quantify diurnal stress signatures for drought phenotyping in Mediterranean environments.
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BibTeX
@article{toro2026vapor,
title = {{Vapor pressure deficit normalizes diurnal photochemical reflectance index for repeatable drought phenotyping of Prunus rootstocks in Mediterranean climates}},
author = {Guillermo Toro and Paula Pimentel and Ariel Salvatierra and Ismael Opazo and Félix Estrada and Gonzalo A. Díaz and José Cares and Claudia Moggia and Gustavo A. Lobos},
journal = {Frontiers in Plant Science},
year = {2026},
month = oct,
doi = {10.3389/fpls.2026.1878667},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1878667/full},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Vapor pressure deficit normalizes diurnal photochemical reflectance index for repeatable drought phenotyping of Prunus rootstocks in Mediterranean climates
AU - Guillermo Toro
AU - Paula Pimentel
AU - Ariel Salvatierra
AU - Ismael Opazo
AU - Félix Estrada
AU - Gonzalo A. Díaz
AU - José Cares
AU - Claudia Moggia
AU - Gustavo A. Lobos
PY - 2026
DA - 2026/10/21
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1878667
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1878667/full
AB - Breeding programs need field-ready traits to compare rootstock drought performance under fluctuating atmospheric demand, particularly in Mediterranean climates where vapor pressure deficit (VPD) can increase abruptly during the day and confound midday “snapshot” screening. We present a VPD-based method to normalize and decompose diurnal dynamics of the photochemical reflectance index (PRI) into repeatable components. Six Prunus rootstocks genotypes were grown under well-watered (WW) and water-deficit (WD; 40% of field capacity) conditions. Leaf PRI was measured hourly (10:00–18:00) on three days spanning VPDmax ≈ 4.9–3.3 kPa, while midday gas exchange and leaf water potential were measured on two days. PRI relationships with incident radiation were weak and variable across genotypes and dates, whereas PRI–VPD trajectories were structured and consistently separated WW and WD conditions. For each genotype, date, and water-regime, PRI–VPD regressions were fitted and decomposed into (i) basal PRI at a common reference VPD (VPDref = 2.0 kPa), (ii) the diurnal PRI–VPD slope, and (iii) WW–WD separation at VPDref. Basal PRI and WW–WD separation produced stable genotype rankings across days (Spearman ρ ≈ 0.8–0.9). Across genotypes, water-deficit–induced changes in PRI (WD relative to WW) tracked changes in stomatal conductance (gs) and transpiration (E). This VPD-normalized decomposition provides a scalable optical trait to quantify diurnal stress signatures for drought phenotyping in Mediterranean environments.
SN - 1664-462X
ER -