Reliability of Greenhouse Screening for Early Selection of <i>Eucalyptus</i> Clones Resistant to <i>Erwinia psidii</i>

ABSTRACT Bacterial blight caused by Erwinia psidii , has become an emerging and severe threat to Eucalyptus production in Brazil. Breeding for resistance remains the most effective strategy for disease management, yet the reliability of early‐stage screening under controlled conditions as a predictor of field performance has not been fully validated. This study aimed to evaluate the predictive reliability of early‐stage selection of resistant genotypes under standardized greenhouse inoculation and symptom expression in field trials under natural high pathogen inoculum pressure. A set of Eucalyptus clones was assessed for disease severity in both conditions, and statistical analyses were performed to determine the predictive value of controlled‐environment phenotyping. Genetic parameters were estimated using REML/BLUP, and the correlation between early and field evaluations was analysed. The results revealed high genetic variability and broad‐sense heritability ( = 0.98 in greenhouse; = 0.83–0.92 in field). A significant correlation ( r = 0.73) was observed between greenhouse and field responses, with the early screening showing the highest accuracy for correctly classifying resistant clones. Greenhouse‐based screening provides a strong indication of field resistance, highlighting its utility for early selection in breeding programs. These findings reinforce the role of integrated screening strategies in accelerating development of resistant clones, ensuring sustainable management of E. psidii in Eucalyptus field stands.