ROOTSTOCK AND SCION INTERACTIONS UNDER CONDITIONS OF SOIL WATER DEFICIT IN AVOCADO

<p><strong>Background.</strong> Drought is the main factor that reduces crop yield, and grafting is used to confer resistance traits. <strong>Objective.</strong> The effect of water deficit on water relations, gas exchange, and proline content was determined in two avocado cultivars, ‘Colín V-33’ and ‘Hass’, grafted onto three clonal rootstocks (‘Colin V-33’ (C), ‘Fuerte’ (F), and ‘Hass’ (H)). <strong>Methodology.</strong> Two-year-old avocado plants of ‘Colín V-33’ and ‘Hass’ were grafted onto three rootstocks: ‘Colin V-33’, ‘Fuerte’, and ‘Hass’. The plants were grown in a greenhouse for 1.4 years. From that point, half of the grafted plants remained without irrigation, while the other half was watered every other day. Stomatal conductance and CO<sub>2</sub> assimilation were measured daily, and on day 13, soil and leaf samples were taken for water relations and leaf samples for proline content. <strong>Results.</strong> The cultivar ‘Colin V-33’ and its combinations showed a conductance of 132 mmol m<sup>-2</sup> s<sup>-1</sup>, while ‘Hass’ reached 150 mmol m<sup>-2</sup> s<sup>-1</sup>. Both decreased after 7 days without irrigation, with variations in their combinations. CO<sub>2</sub> assimilation followed a similar pattern. In well-watered plants, there were no differences in water potential (Y<sub>w</sub>), but in non-irrigated plants, ‘Colin V-33’ showed a greater decrease in leaf Yw, whereas in ‘Hass’, this occurred in the H/H and H/F combinations. The osmotic potential (Y<sub>p</sub>) was lower in non-irrigated plants with ‘Hass’, especially in C/H and H/H (-1.80 and -1.81 MPa respectively). Turgor potential (Y<sub>r</sub>) was unaffected. Proline concentration was higher in all combinations, particularly in H/H and H/F. <strong>Implications.</strong> Grafting is useful for identifying cultivars sensitive or resistant to water deficit. <strong>Conclusion.</strong> The combinations with ‘Colin V-33’ show the best water use efficiency and greater resistance to water deficit. The scion/rootstock interaction significantly affects gas exchange, water relations, and proline concentration under water deficit. Low proline concentrations in this species appear linked to water deficit resistance.</p>