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Background and aims <p>Rootstocks are widely used in walnut to modulate vigor and stress tolerance, yet the extent to which rootstock traits translate into scion-level drought performance remains uncertain. We evaluated whether contrasting clonal rootstocks (‘RX1’, ‘VX211’) and a <i>Juglans regia</i> seedling rootstock modify root hydraulic capacity and, in turn, the water status and gas exchange of potted ‘Chandler’ under progressive water deficit.</p> Methods <p>Chandler’ was grafted onto <i>J. regia</i> seedlings (CH/JU) or onto clonal ‘RX1’ and ‘VX211’ (CH/RX1, CH/VX211). Ungrafted ‘RX1’ and ‘VX211’ were included to characterize genotype-dependent traits in the absence of a graft union. Plants were maintained under well-watered (WW) or progressive water deficit (WD) conditions. We measured trunk diameter, root dry mass, root hydraulic conductance and conductivity (Kr25, Lr25; HPFM), leaf water potentials, gas exchange, turgor loss point (TLP) and hydroscape area (HA), and whole-plant transpiration in WD (gravimetric).</p> Results <p>WD reduced gas exchange, whereas root dry mass and trunk diameter did not differ between water treatments. Root biomass and hydraulic traits differed among scion–rootstock combinations, with CH/JU and ‘VX211’ generally exhibiting higher Kr25 and/or Lr25 than ‘RX1’. Across grafted combinations, TLP was similar and HA values were low, while CH/JU showed a comparatively smaller HA.</p> Conclusions <p>Under the conditions and drought trajectory tested, rootstock-related differences in root traits were not consistently mirrored by large differences in scion water status or gas exchange. These results suggest that rootstock effects on drought performance may be context dependent and warrant further evaluation across scion genotypes and under field conditions.</p>

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Conservative water-use strategy in walnut (Juglans regia) cv. ‘Chandler’ grafted onto rootstocks differing in root hydraulic conductance and vigor

  • 期刊论文

  • 发表日期：

    2026年1月24日

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  • Adolfo Pardo,
  • Rodrigo Infante,
  • Jaime Otárola,
  • Marco Garrido-Salinas

摘要

Background and aims

Rootstocks are widely used in walnut to modulate vigor and stress tolerance, yet the extent to which rootstock traits translate into scion-level drought performance remains uncertain. We evaluated whether contrasting clonal rootstocks (‘RX1’, ‘VX211’) and a Juglans regia seedling rootstock modify root hydraulic capacity and, in turn, the water status and gas exchange of potted ‘Chandler’ under progressive water deficit.

Methods

Chandler’ was grafted onto J. regia seedlings (CH/JU) or onto clonal ‘RX1’ and ‘VX211’ (CH/RX1, CH/VX211). Ungrafted ‘RX1’ and ‘VX211’ were included to characterize genotype-dependent traits in the absence of a graft union. Plants were maintained under well-watered (WW) or progressive water deficit (WD) conditions. We measured trunk diameter, root dry mass, root hydraulic conductance and conductivity (Kr25, Lr25; HPFM), leaf water potentials, gas exchange, turgor loss point (TLP) and hydroscape area (HA), and whole-plant transpiration in WD (gravimetric).

Results

WD reduced gas exchange, whereas root dry mass and trunk diameter did not differ between water treatments. Root biomass and hydraulic traits differed among scion–rootstock combinations, with CH/JU and ‘VX211’ generally exhibiting higher Kr25 and/or Lr25 than ‘RX1’. Across grafted combinations, TLP was similar and HA values were low, while CH/JU showed a comparatively smaller HA.

Conclusions

Under the conditions and drought trajectory tested, rootstock-related differences in root traits were not consistently mirrored by large differences in scion water status or gas exchange. These results suggest that rootstock effects on drought performance may be context dependent and warrant further evaluation across scion genotypes and under field conditions.