Scion power: How one grapevine variety outsmarts drought at the molecular level
image: Experimental design on greenhouse conditions at three different water deficit levels depending on the hydric potential of leaves (Mild: −0.6 MPa ≤ Ψstem ≤ −0.9 MPa; High: −0.9 MPa ≤ Ψstem ≤ −1.4 MPa; Extreme: Ψstem ≥ −1.4 MPa) on 2-year study (2020 and 2022).
Credit: Horticulture Research
Understanding how grapevines respond to drought is key to future-proofing viticulture in a changing climate. In a recent study, scientists examined how two grapevine cultivars—Callet and Merlot—respond when grafted onto the same rootstock and exposed to increasing levels of water deficit. Callet, a drought-adapted local variety, exhibited stronger resilience, activating precise gene expression responses in both shoots and roots. These responses were linked to heightened sensitivity to abscisic acid (ABA), better water use regulation, and reduced oxidative stress. In contrast, Merlot showed weaker molecular coordination under drought conditions. The findings spotlight the dominant role of the scion in shaping drought response and suggest new strategies for selecting optimal grapevine pairings in the face of climate challenges.
As climate change intensifies drought conditions, vineyards around the world are under increasing pressure. Water stress diminishes grape yield and alters fruit quality, threatening the economic and ecological stability of viticultural systems. Yet not all grapevine varieties respond to drought in the same way. Near-isohydric cultivars like Callet tightly regulate water loss, while anisohydric types like Merlot are more permissive. These physiological differences stem from varying sensitivities to plant hormones like abscisic acid (ABA) and divergent gene expression pathways. Recent evidence also points to complex interactions between scion and rootstock as critical factors in drought response. Given this intricate web of traits, there is an urgent need to decode how grafted grapevines adapt at both molecular and whole-plant levels.
New research from CBGP-INIA, the University of Oviedo, and the Universitat de les Illes Balears, published (DOI: 10.1093/hr/uhae291) in Horticulture Research (February 2025), offers crucial insights into this puzzle. The team investigated how the genetic identity of the scion influences drought adaptation in grafted grapevines. By comparing physiological, hormonal, and transcriptomic responses in Callet and Merlot—both grafted onto 110 Richter rootstocks—they found that the scion’s genotype plays a decisive role in orchestrating the plant’s defense strategy under drought stress.
The study revealed striking differences in how each grafted combination responded to escalating water stress. Callet/110 Richter maintained higher water use efficiency and photosynthetic activity even under extreme drought, supported by robust activation of genes linked to ABA response, sugar transport, and oxidative stress defenses—particularly from the BURP and MYB gene families. Callet also displayed synchronized gene regulation across shoots and roots, enhancing ion homeostasis and lignin biosynthesis. By contrast, Merlot/110 Richter exhibited minimal root gene activity and a more fragmented response. Metabolite analysis further showed higher levels of osmoprotectants like myo-inositol and γ-aminobutyric acid (GABA) in Callet, consistent with its transcriptomic patterns. Notably, although ABA levels rose in both cultivars under drought, only Callet effectively translated that signal into coordinated molecular action—underscoring the scion's central command over the whole-plant response.
“By analyzing gene expression and physiological responses under increasing water stress, we found that the scion essentially guides the whole plant’s adaptation strategy,” said lead author Dr. Alberto Rodriguez-Izquierdo. “Callet’s enhanced ABA sensitivity and stress-responsive gene regulation translated into a more specific and coordinated defense compared to Merlot. These findings underscore the importance of choosing the right scion–rootstock pairings, especially as climate change intensifies drought frequency in viticultural regions.”
The findings carry important implications for viticulture and climate-resilient agriculture. Identifying key gene families such as BURP and MYB provides a path toward molecular breeding of drought-tolerant grapevines. Perhaps more importantly, the study reveals that optimizing scion selection—not just rootstock—may be crucial for improving whole-plant drought resilience. This work lays the foundation for future research on hormonal signaling and shoot–root communication, offering a strategic roadmap to sustain grape production in increasingly arid landscapes.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae291
Funding information
This study was supported by the Research and Science Ministry of Spain (project RTI2018-094470-R-C21 and PID2021-1255750R-C21).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.