Uncovering Cercospora species affecting sugar beet in Iran with rapid and accurate detection of C. beticola using LAMP assay

Cercospora leaf spot (CLS) is a major disease impacting global sugar beet cultivation and yield. This study investigated the potential diversity of Cercospora species causing CLS in Iranian sugar beet. Fungal isolates were characterized using integrated morphological and multi-gene sequence analyses. Subsequently, the possibility of rapid and specific diagnosis of the dominant pathogen using Loop-Mediated Isothermal Amplification (LAMP) was assessed. Infected leaves were collected from Ardabil, West Azerbaijan, Khorasan Razavi, Semnan, Mazandaran, Khuzestan, and Golestan provinces across the country. Genomic regions of actA, cmdA, gapdh, his3 and tef1 were amplified and sequenced. Phylogenetic results revealed that two species, Cercospora beticola and Cercospora gamsiana, are involved in causing cercospora leaf spot of sugar beet in Iran from which C. beticola was the dominant species. The LAMP-specific primers designed based on the gapdh gene region successfully discriminated C. beticola from C. gamsiana and other Cercospora species, as well as from some other fungal genera such as, Alternaria, Cladosporium, Curvularia, Ramularia and Stemphylium. The LAMP assay in this study demonstrated a detection limit of 50 fg μL^-1. This study found C. beticola to be the dominant species in Iranian sugar beet fields. The LAMP technique proved effective for rapid, accurate diagnosis, aiding optimized disease management and control strategy selection.