Can high-throughput 3D and multispectral phenotyping detect early grapevine responses to water stress events?

Phenotyping is pivotal in biological and agronomical research, enabling the characterization of phenotypic traits in living organisms. Recent advancements have led to the development of innovative platforms that enhance the precision of phenotyping, integrating genetic and ecophysiological analyses for a comprehensive understanding of plant growth under controlled conditions. These technologies are instrumental in studying plant responses to environmental stresses, such as drought, which disrupts water balance in plants. This study focuses on the adaptability of grafted grapevines (Vitis vinifera L.) to drought stress, emphasizing the rootstock influence on scion performance. The experimental trial was performed at 'PhenoPlant,' a cutting-edge phenotyping platform at the University of Torino, DISAFA. PhenoPlant is a non-invasive, high-throughput tool that employs advanced technologies, including a PlantEye sensor for 3D vision and multispectral imaging, measurement of the potted-plant evapotranspiration by gravimetric technique, water potential assessment and Infra-Red Gas Analysis for leaf-to-atmosphere gas exchange detection. Grapevine responses to drought stress across eleven scion/rootstock combinations, featuring clones of Nebbiolo and Pinot Noir grafted onto rootstocks with varying drought tolerance were assessed. A 13-day drought-recovery experiment on grafted 1-year old plants, three months after in-pot-transplanting revealed significant differences in drought responses among rootstock/scion combinations. Drought-tolerant rootstocks (e.g., 1103 P, 110 R, 140Ru, M2) maintained stable spectrometric indices (e.g.: GLI, Green Leaf Index) mirroring morpho-physiological ones (e.g., Leaf Surface Angle - SA, Stomatal Conduction - gs, Stem Water Potential and Evapotranspiration), unlike their less tolerant counterparts (e.g., Kober 5BB, SO4, 420 A, Gravesac). In particular, after 10 days of water removal, a reduced variation in some traits was observed in tolerant combinations (SA: 39-44°; GLI ≈ 0.33-0.35; gs: 34.5-45.4 mmol H₂O·m⁻²·s⁻¹), while decreasing markedly in sensitive ones (SA: 27-35°; GLI: 0.28-0.32; gs: 8.6-10.8 mmol H₂O·m⁻²·s⁻¹), underscoring the rootstock's crucial role in drought response, independently from scion cultivar. These findings are vital for a fast and early assessment of multiple rootstock/scion combinations to optimize grapevine management and breeding programs for enhanced performance under water-limited conditions. Intrinsic limitations of the measurement system and aspects to be considered to export results from the platform to the vineyard are presented and discussed.