How to validate an operational clone? A case study of the hybrid Eucalyptus urophylla × Eucalyptus dunnii in vegetative propagation

Initial selection of genetic materials may be hindered by the various stages required before a genotype can be operationally deployed on a commercial scale. In this context, Eucalyptus hybrids, although highly significant to Brazilian forestry, may present rooting difficulties and/or developmental abnormalities when propagated via mini-cutting, such as plagiotropic growth. This study aimed to evaluate different concentrations of IBA on the survival and rooting of mini-cuttings of Eucalyptus urophylla × Eucalyptus dunnii, to analyze their initial growth and development after planting in comparison to operational clones, and to validate the classification of the hybrid clone as operational. The effects of four IBA concentrations (0, 1,500, 3,000, and 4,500 mg L⁻¹) on the survival and rooting of mini-cuttings were assessed. After 120 days of rooting, the seedlings produced under 0 and 1,500 mg L⁻¹ treatments were transplanted into pots, where they remained for an additional 180 days. Morphological traits such as height, root collar diameter, and Dickson Quality Index (DQI) were evaluated, as well as the intensity of plagiotropic growth exhibited by the hybrid. The 1,500 mg L⁻¹ IBA concentration improved rooting performance but also induced higher rates of growth abnormalities. The hybrid exhibited a genetic predisposition to growth anomalies, which were exacerbated by IBA application Despite the significant rooting and biomass accumulation of the E. urophylla × E. dunnii hybrid, the studied clone is not yet suitable for commercial propagation due to its plagiotropic growth pattern.