Etiology of Alternaria Leaf Blight on Potato: Pathogen Identification, Host Range, and Aggressiveness Testing

Abstract

Alternaria leaf blight is an important foliar disease affecting potato cultivation and causing substantial reductions in tuber yield and quality under favorable environmental conditions. The present investigation was conducted to determine the etiology of Alternaria leaf blight on potato through pathogen identification, host range evaluation, and aggressiveness testing of isolated strains. Diseased leaf samples exhibiting typical blight symptoms were collected from infected potato fields, and the pathogen was isolated using standard microbiological techniques. Morphological characteristics including colony appearance, conidial structure, septation, and sporulation pattern were examined for preliminary identification. Molecular confirmation of the pathogen was performed using internal transcribed spacer (ITS) region sequencing, which verified the association of Alternaria species with the disease. Pathogenicity tests conducted under controlled conditions successfully reproduced characteristic symptoms, thereby fulfilling Koch’s postulates. Host range studies revealed that the pathogen was capable of infecting several solanaceous crops with varying levels of susceptibility. Aggressiveness testing among different isolates demonstrated significant variability in lesion development, disease severity, and infection efficiency on potato plants. Highly aggressive isolates produced larger necrotic lesions and rapid tissue damage compared to less virulent strains. The integration of morphological, molecular, and pathogenicity analyses provided comprehensive insights into the biology and variability of the pathogen population. The findings of this study contribute to improved disease diagnosis and support the development of effective management strategies for controlling Alternaria leaf blight in potato production systems.