Pathogenicity of Botryosphaeriaceae and Phytophthora species associated with Paulownia dieback, canker and root rot in Italy

In recent years, an unusual decline and mortality has been observed inPaulownia plantations throughout the Marche region (Central Italy). Given the eco-nomic importance of this emerging forest crop, a study was conducted to determinewhich pathogens are directly involved in this syndrome. Field surveys performed intwo plantations revealed the widespread occurrence of severe disease symptoms suchas leaf chlorosis, crown thinning, shoot and branch dieback, sunken cankers, epicormicshoots and root rot. Disease incidence was also assessed by aerial remote sensing (RS)technologies using drones. Symptomatic samples collected from both stem and roottissues yielded fungal and fungal-like colonies representing two distinct families: Bot-ryosphaeriaceae and Peronosporaceae. Morphological and DNA sequence data revealedfive distinct species, identified as Macrophomina phaseolina and Botryosphaeria doth-idea (Botryosphaeriaceae), Phytophthora pseudocryptogea, P. citrophthora and P. eryth-roseptica (Peronosporaceae). Given that all species are reported here for the first timeon Paulownia, Koch’s postulates were satisfied inoculating the three Phytophthora spe-cies and two Botryosphaeriaceae at the collar of the stem of potted 1-year-old rootedcuttings in June 2023. Thirty days after inoculation, all plants showed the same symp-toms as those observed in the field.