Molecular and pathological characterization of Alternaria burnsii as an emerging foliar pathogen of eggplant (Solanum melongena L.)

The present study reports Alternaria burnsii as the causal agent of leaf spot disease on eggplant (Solanum melongena L.) for the first time. Symptomatic leaves exhibiting dark necrotic lesions with yellow margins were collected from multiple locations in Basrah province, southern Iraq. The fungus was isolated on potato dextrose agar which produced creamy-orange to white colonies with a cottony to velvety texture. Microscopic examination revealed oval to rectangular conidia with 3-6 transverse septa, formed in chains of 4-8 conidia, consistent with characteristics of the genus Alternaria. Molecular identification based on ITS sequencing confirmed the isolate as A. burnsii, forming a distinct subclade within the species complex and the sequence was deposited in GenBank under accession number PV961372.1. Pathogenicity assays under greenhouse conditions confirmed its virulence on eggplant, with necrotic lesions appearing five days after inoculation and progressively expanding thereafter. These findings demonstrate that A. burnsii is a previously unreported foliar pathogen of eggplant and highlight its potential threat to economically important vegetable crops.