Collection, isolation and characterization of Sclerotinia sclerotiorum, an emerging fungal pathogen causing white mold disease

Sclerotinia sclerotiorum (Lib.) de Bary caused white mold disease with a wide distribution worldwide. For the control of the disease, it is fundamental to understand the identification, morphology, and genetic diversity of the fungus. The objective of this study was to collect and characterize S. sclerotiorum isolates from different regions of the country. The characteristics evaluated for the mycelium characterization were: the time required for the fungus to occupy the plate; density of the formed mycelium; coloration of the colonies and mycelia growth rate. Sclerotia assessments were based on the time for the formation of the first sclerotia total number formed per plate, the format of distribution in the plate, and the shape of the sclerotia formed by the isolates. Variability was observed for colony colour, type of growth, the diameter of mycelia growth, sclerotia initiation, and number and pattern of sclerotia formation among the isolates. The evaluated populations presented wide variability for the cultural and morphological characteristics, being predominant in the whitish colonies with fast-growing habitats. The majority of isolates produced a higher number of sclerotia near the margin of the plates and with diverse formats. Phylogenetic analysis revealed that the isolates belonged to a similar group of publicly available S. sclerotiorum and were dissimilar from the group of S. minor, and S. trifolium and distinctly differ from S. nivalis group. The present study is the first evidence for morphological and genetic diversity study of S. sclerotiorum in Bangladesh. Therefore, this report contributes to more information about the morphological and genetic diversity of S. sclerotiorum and can be useful in implementing effective management strategies for the pathogen which caused white mold disease.