First Report of Southern Blight Disease of Sugar Beet, Beta vulgaris Caused by Athelia rolfsii in Syria

Abstract

Symptoms of yellowing, leaf wilting, brown-black lesions, root rot with white mycelium grown on it, were observed in sugar beet fields (Hama Governorate, Syria) during the summer of 2022. The fungal pathogen was identified as Athelia rolfsii as a species that causes sugar beet root rot for the first time in Syria. The classification of the pathogen was based on the morphological and cultural taxonomic characteristics of the mycelium and the sclerotia of the fungus grown on the nutrient culture medium PDA. The mycelium was cottony, and the fungal hyphae had clamp connections and brown sclerotia with diameters ranging from 0.5 to 1 mm. Within 8 days of incubation at a temperature of 25±3°C, the isolate grew well on PDA medium, with radial growth at a rate of 3-4.5 mm/day. Koch’s postulates confirmed that the fungus A. rolfsii is the causative agent of sugar beet root rot, and was not a secondary fungal contaminant.

Keywords:

Athelia rolfsii, Sclerotium rolfsii, sugar beet, Syria.