مطالعه اثر عصاره‌های آبی، استونی، هگزانی و متانولی به‌لیمو، موره و گزنه بر کنترل قارچ بیمارگر ساق زخم توتون (Rhizoctonia solani) در شرایط آزمایشگاه

Fungal of tobacco sore shin are important phytopathogens distributed worldwide and can cause yield losses in tobacco growing countries. The cultivated area of the plant in the world is more than 5 million hectares and the total production of tobacco is more than 7 million tons per yearThemanagment of fungal soilborne pathogens are accomplished through the use of pesticides, resistant varieties, biological control, use of plant extracts and oils and etc is done. The use of plant extracts for management of this disease is preferable because pesticides are expensive and may pollute the environment. This design investigated the inhibitory effects of some medicinal plant extracts on growth of Rhizoctoniasolani the cause of tobacco sore shin and selection of a suitable solvent for extraction is performed in the laboratory. In this study, crude extracts of 3 plant species were tested in vitro for antifungal activity against R. solani. The plant were extracted with water, acetone, hexzan and methanol were carried out in facturial with three factors including:crude extracts (3 plant species) and solvent (4solvent) and 6 cocentration (0, 250, 500, 1000, 2000 and 4000 ppm) based on Completely Randomized Design with 3 replications in Tirtash Research and Education Center in 2017. The minimum inhibitory concentration of each extracts was determined by agar diffusion method. Results indicated that crude extracts of lemon verbena and nettle have remarkable antifungal activity.The inhibitory effect of lemon verbena methanolic extracts on the concentrationsin 1000, 2000 and 4000 ppm and lemon verbena hexzan extractson the concentrationsin 2000 and 4000 ppm and also lemon verbena acetone extract on the concentrationin 4000 ppm with 88.8%, 92.5%, 96.2%, 88.8%, 92.5% and 88.8% respectivelyinhibitory effect of the mycelial growth of the fungus was greatestand they were all in a group. The lemon verbena water extract on the concentrationin 4000 ppm with 77.7% inhibitory effectwas ranked next.methanol were the best solvent to extract antifungal compounds. Therefure, it is likely possible using plant extracts of this plants, especially lemon verbena and nettlefor the control of tobacco sore shin disease