Antifungal activity of Trachystemon orientalis L. aqueous extracts against plant pathogens

Trachystemon orientalis (L.) G. Don (Boraginaceae), recognized as Hodan, Kaldirik in Turkey, is a perennial medical plant. The plant materials of Kaldirik were collected from Saz village of Düzce province (Turkey) in 2010 to determine its antifungal effect. The aqueous extracts obtained from leaves, roots and flowers and were applied against five plant pathogen fungi which they are respectively Ascochyta rabiei (Pass) Labr., Fusarium oxysporum (Schlechtendahl:Fries) f. sp. melonis (Snyder & Hansen), Fusarium oxysporum (Schlechtendahl:Fries) f. sp. radicis-lycopersici (Jarvis & Shoemaker), Verticillium dahliae (Kleb.) and Rhizoctonia solani Kühn. The original concentration of extracts obtained for fungal studies was 10% as. Sterile potato dextrose agar (PDA) was cooled in a water bath at 40°C, and the extracts were mixed with the sterile 250 ml PDA to obtain final concentrations of 1%, 3%, 5%, 7% 10% and 20%. Then, the PDA was poured into 60-mm Petri plates (10 ml plate-1) and a agar disc (5 mm in diameter) of plant pathogens (from 7 day-old PDA cultures) were inoculated on medium. They were incubated at 25±2°C for 7 days in incubator. As a result of the study, the aqueous extract of flower showed maximum inhibitory effect against the mycelial growth of plant pathogens, it was respectively followed by leaf and root extracts. Flower extract completely inhibited mycelial growth of A. rabiei, V. dahliae and R. solani in all applied doses. According to the result of the study, the first time was identified of T. orientalis aqueous extracts, have high antifungal effect against plant pathogens.