SALT-STRESS RESPONSES OF EUCALYPTUS CLONES: GROWTH AND SEEDLING QUALITY AT THE NURSERY STAGE

Soil salinization impairs the establishment of planted forests in irrigated areas, and the selection of salt-tolerant genotypes at the nursery stage is a relevant preliminary step in Eucalyptus breeding programs. This study evaluated the growth and seedling quality of four commercial clones (E. urophylla × E. grandis, E. tereticornis, and E. grandis) subjected to four NaCl concentrations (0, 30, 60, and 90 mM) in a 4 × 4 factorial completely randomized design with five replicates, conducted over 60 days under nursery conditions. Plant height (H), root collar diameter (RCD), shoot number (SN), shoot dry mass (SDM), and root dry mass (RDM) were measured, and the robustness index (RI), lignification index (LI), and Dickson quality index (DQI) were calculated. Clone I144 (E. urophylla × E. grandis) exhibited the highest mean values for H (77.4 ± 8.9 cm), RCD (0.80 ± 0.08 cm), SN (53 ± 13 shoots), SDM (16 ± 4 g), and LI (2.6 ± 0.4) at 60 days, along with the lowest RI among all evaluated clones. DQI increased with NaCl concentration in I144, a pattern not observed in the remaining clones. These results indicate that I144 maintains superior growth and seedling quality under a salinity gradient of up to 90 mM NaCl, distinguishing it from the E. tereticornis and E. grandis clones, which were more adversely affected by salt stress.