Peronospora hyoscyami is a pathogenic fungus that causes downy mildew disease in plants. It predominantly infects the species of Solanaceae family, including tobacco, tomato, potato, and henbane. The disease caused by P. hyoscyami leads to reduced yields and poor quality of the plant products. There are several synonyms for Peronospora hyoscyami, which include Phytophthora hyoscyami, Bremia hyoscyami, and Hyaloperonospora hyoscyami. These synonyms refer to the same pathogenic fungus and are used interchangeably among researchers and plant pathologists. Identifying the presence of P. hyoscyami in crop plants and using appropriate control measures is crucial to prevent yield losses and maintain the quality of plant products.