Diaporthe cercidis causing leaf blight on Magnolia grandiflora in China

Magnolia grandiflora (Southern magnolia), a globally cultivated ornamental species in the Magnoliaceae family, has recently been threatened by an emerging leaf blight disease. In June 2024, we observed severe disease progression on M. grandiflora trees in Nanchang, Jiangxi Province, with 100 % incidence rate in sampled specimens. In order to clarify the cause of the disease, Koch's postulates were completed by isolation of fungal strains from pathological tissues, pathogenicity tests performed by artificially damaging leaves, and re-isolation. The pathogen was characterized as Diaporthe cercidis based on conidial morphology and multi-locus phylogenetic reconstruction incorporating ITS (internal transcribed spacer), TUB (β-tubulin), and TEF (translation elongation factor 1-α) sequences. This study establishes the first definitive evidence of D. cercidis as an etiological agent of M. grandiflora leaf blight worldwide. Our findings expand the known host range of Diaporthe species and provide critical baseline data for developing targeted management strategies in urban landscaping systems.