New Report of Alterneria alternata Causing Leaf Spot Disease on Neolitsea pallens (Lauraceae) in Pakistan

Abstract

During June–August 2025, necrotic leaf spot symptoms were frequently observed on Neolitsea pallens in the district Swat, Pakistan. The symptoms were found associated with many individual trees, affecting the overall vegetative growth and vigor under field conditions. To determine the causal agent, the fungal pathogen was isolated from multiple symptomatic leaves and subsequently morphomolecularly characterized. Genomic DNA was extracted from the isolated pathogen, ITS, and Alt‐a1 loci were amplified and sequenced. The BLAST search revealed 100% similarity with Alternaria alternata (CBS 121455). Further, the identification was supported by morphological characteristics and phylogenetic analyses. Pathogenicity assays were conducted using both detached leaf assay and foliar spray technique under controlled conditions. Typical field symptoms were reproduced on inoculated leaves, whereas the control leaves remained asymptomatic. For further confirmation, the pathogen was successfully reisolated and cultured from the symptomatic tissues, thereby fulfilling Koch's postulates. Importantly, this study represents the first global record of A. alternata causing necrotic leaf spot on N. pallens in Pakistan.