Morphological, Pathogenic and Molecular Characterization of Sclerotinia sclerotiorum, the Causal Agent of White Rot of Cabbage (Brassica oleracea var. capitata), in Serbia

Sclerotinia sclerotiorum is a globally distributed necrotrophic pathogen with a broad host range, including many Brassicaceae crops. In 2021, white rot symptoms on cabbage were observed in 12 commercial fields in the northern part of Serbia. Twelve representative isolates of S. sclerotiorum, forming white colonies and black sclerotia, were selected for characterization and comparison with an isolate from sunflower, as the most important host plant in Serbia. The isolates showed significant variation in growth rate and sclerotia production, while ITS sequence analysis revealed the complete nucleotide identity and all isolates grouped within the major phylogenetic clade of S. sclerotiorum. Despite the low diversity of the global population of S. sclerotiorum, forty-four haplotypes were identified, with one predominant haplotype encompassing all Serbian isolates. When six Brassicaceae species (cabbage, cauliflower, broccoli, kale, mustard, and oilseed rape) and sunflower were inoculated, sunflower was found to be the most and cauliflower the least susceptible, while isolates from cabbage were generally more aggressive than those derived from sunflower. This work represents the first detailed characterization of S. sclerotiorum infecting cabbage in Serbia and highlights its genetic uniformity and differential pathogenic potential, which are critical factors for integrated disease management and crop rotation planning in Brassicaceae agroecosystems.