Pathogenicity and Molecular Identification of Pestalotiopsis spp. Causing Leaf Blight on Eucalyptus Plantations

Abstract

Leaf blight symptoms in Eucalyptus plantations have increasingly been associated with fungal infections leading to premature defoliation and reduced plantation productivity. Diseased leaves exhibiting necrotic lesions with characteristic marginal browning were collected from multiple plantations for pathogen isolation and characterization. Fungal isolates obtained on potato dextrose agar consistently produced Pestalotiopsis-like conidia, and morphological examination confirmed the presence of fusiform, septate spores with apical appendages. Molecular identification based on ITS rDNA sequencing further validated the isolates as belonging to Pestalotiopsis spp., with phylogenetic analysis clustering them closely with known pathogenic strains reported from woody hosts. Pathogenicity assays conducted under controlled greenhouse conditions demonstrated that inoculated Eucalyptus seedlings developed typical leaf blight symptoms within 7–10 days post-inoculation, fulfilling Koch’s postulates. Disease severity varied among isolates, indicating differential virulence levels. Environmental parameters such as high humidity and moderate temperature were found to favor rapid disease progression. The study highlights the significant pathogenic potential of Pestalotiopsis spp. in eucalyptus cultivation systems and underscores the need for early detection strategies. Integrated disease management approaches, including the use of resistant clones, sanitation practices, and monitoring of nursery stock, are recommended to limit pathogen spread. Molecular characterization provides reliable diagnostic markers for rapid identification, aiding in the development of targeted management strategies. These findings contribute to improved understanding of the epidemiology of leaf blight in Eucalyptus and emphasize the importance of combining classical mycology with molecular tools for accurate pathogen identification and disease management in commercial plantations and support sustainable forestry production in affected regions globally under changing climatic conditions.