First report of Calonectria pseudoreteaudii causing leaf blight on Populus deltoides in India

Populus deltoides, an economically important and fast-growing tree species, was observed exhibiting severe foliar blight symptoms during disease surveys conducted recently in northern India. Fungal isolates consistently recovered from diseased leaf tissues displayed morphological characteristics typical of the genus Calonectria. Species identification was achieved using a polyphasic taxonomic approach integrating morphological characterization with multilocus phylogenetic analyses based on partial sequences of the actin (act), internal transcribed spacer (ITS), translation elongation factor 1-α (tef1), and β-tubulin (tub2) gene regions, which confirmed the pathogen as Calonectria pseudoreteaudii. Pathogenicity was demonstrated through detached-leaf assays as well as live-plant leaf inoculation experiments, both of which consistently reproduced disease symptoms comparable to those observed under natural field conditions. Re-isolation of the pathogen from inoculated tissues fulfilled Koch’s postulates. This study represents the first report of C. pseudoreteaudii causing leaf blight on P. deltoides in India and, to our knowledge, worldwide, thereby extending the known host range of this destructive pathogen.