ASSESSMENT AND SUSTAINABLE CONTROL OF WHITE RUST (PUCCINIA HORIANA HENN.) IN THE CHRYSANTHEMUM CULTIVARS COLLECTION OF THE IAŞI BOTANICAL GARDEN (ROMANIA)

Chrysanthemum white rust (CWR), caused by Puccinia horiana Henn., is a quarantine disease that poses a serious threat to chrysanthemum production under protected cultivation. This study aimed to evaluate the incidence, severity, and cultivar-specific responses to CWR in a greenhouse collection of Chrysanthemum × grandiflorum Ramat. at the “Anastasie Fatu” Botanical Garden of Ia?i, Romania. A total of 35 cultivars (1,120 plants) were monitored under uniform greenhouse conditions between 2020 and 2023 growing seasons. Disease assessment was based on systematic visual inspections, microscopic confirmation of the pathogen, and quantitative evaluation using Disease Incidence, Disease Severity Index, and standardized Combined Score integrating both parameters. Cultivars were classified into susceptibility categories ranging from tolerant to highly susceptible. In 2020, disease incidence ranged from 0% in resistant cultivars to over 90% in highly susceptible ones, with corresponding variations in disease severity. The implementation of integrated management strategies, including cultural practices, curative fungicide applications at 13 and 15 weeks after planting, and preventive treatments at 5 weeks after planting, resulted in a significant reduction in disease incidence and severity in 2021. Continuous monitoring combined with preventive treatments in 2022 and 2023 led to the complete suppression of CWR, with no visible symptoms observed across all cultivars. Several cultivars consistently exhibited resistance throughout the study, while others showed high susceptibility under initial disease pressure. The findings demonstrate that the integration of resistant cultivars with early preventive measures and continuous monitoring is essential for the sustainable management of P. horiana in greenhouse chrysanthemum production. This study provides a practical framework for disease assessment and supports informed cultivar selection and integrated disease control strategies for ornamental crops.