Morphological and Molecular Characterization of Cercospora beticola Causing Cercospora Leaf Spot on Sugar Beet

Abstract

Cercospora leaf spot caused by Cercospora beticola is one of the most destructive foliar diseases affecting sugar beet production worldwide, leading to severe reductions in root yield, sugar content, and overall crop quality. The disease is characterized by circular necrotic lesions on leaves, chlorosis, premature defoliation, and reduced photosynthetic efficiency under favorable environmental conditions. Accurate identification and characterization of the pathogen are essential for effective disease management and resistance breeding programs. The present study was conducted to investigate the morphological and molecular characteristics of C. beticola associated with Cercospora leaf spot disease in sugar beet cultivation areas. Diseased leaf samples exhibiting typical symptoms were collected from infected fields, and fungal isolates were obtained using standard isolation and culturing methods. Morphological characterization was performed based on colony appearance, pigmentation, conidial morphology, and growth patterns under laboratory conditions. Molecular identification was carried out using polymerase chain reaction (PCR) amplification and sequencing of conserved genomic regions, followed by phylogenetic analysis to determine genetic relationships among the isolates. Pathogenicity assays were also conducted on healthy sugar beet plants under controlled conditions to confirm the disease-causing ability of the isolates and fulfill Koch’s postulates. The results consistently associated C. beticola with symptomatic sugar beet leaves. Considerable morphological variation was observed among isolates in colony growth, sporulation, and conidial characteristics. Molecular analysis revealed high genetic similarity between the obtained isolates and previously reported C. beticola strains from different sugar beet-growing regions, although some genetic variability was detected among local populations. Inoculated plants developed characteristic leaf spot symptoms, confirming the pathogenic nature of the isolates. The findings provide important insights into the diversity and identification of C. beticola populations affecting sugar beet crops. Understanding the morphological and molecular variability of this pathogen is essential for improving disease diagnosis, epidemiological studies, and integrated disease management strategies aimed at minimizing losses in sugar beet production systems.