Swertia chirayita (Roxb.ex Flem.) Kart (Family: Gentianaceae), is a high value endangered medicinal plant used in traditional therapies. The species is distributed in temperate Himalayas at an altitude of 1200-1500 m amsl. The dried herbage is the source of raw drug. The species is valued for its bitter principles as hepatic stimulant, blood purifier, tonic etc. The bitterness, antihelmintic, hypoglycemic and antipyretic properties are attributed to amarogentin, swerchirin, swertiamarin and other active principles of the herb (Chassot, 2000). The species is on the verge of extinction due to massive unscientific exploitation from its wild natural areas. Considering the demand and importance of genuine chirayita, work on exploration, domestication and development of cultural practices and chemical profiling of S. chirayita has been initiated. S.chirayita suffers from many diseases like seedling blight, Leaf blight, Leaf spot etc. Among them, leaf spot is an important disease. It becomes severe in major chirata growing area of Darjeeling district. Efforts were made to identify and isolate the harmful pathogen. Hence, laboratory experiments were conducted to detect and identify the causative pathogen on leaves of Swertia chirayita collected from naturally contaminated commercial plants. Identification of the pathogen was done on the basis of morphological parameters. Koch’s postulates confirmed the presence of Alternaria alternata.
