Antifungal activity of some plant extracts on mycelial growth of Sclerotinia sclerotiorum, the causal agent of tobacco collar rot

Fungal soilborne pathogens of tobacco are important phytopathogens distributed worldwide and can cause yield losses in tobacco growing countries. The managment of fungal soilborne pathogens are accomplished using chemical pesticides, crop rotation, resistant varieties, biological control, plant extracts and oils, etc. Application of plant extracts is preferable for management of this disease because chemical pesticides are expensive and pollute the environment. In order to evaluate in vitro inhibitory effects of some medicinal plant extracts on growth of Sclerotinia sclerotiorum, the causal agent of tobacco collar rot, and selection a suitable extract solvent, an experiment was carried out as factorial based on a completely randomized design with five replications in Tirtash Research and Education Center laboratory in 2012. Factors were crude extracts at nine levels (extracts of nine plant species), solvent at five levels (water, acetone, hexzan, ethanol and methanol) and cocentration at three levels (0, 1000 and 2000 ppm). The minimum inhibitory concentration of each extract was determined by agar diffusion method. Results indicated remarkable antifungal activity of crude extracts of tobacco, catmint, thyme, fennel, hyssop and badrashbi on Sclerotinia sclerotiorum. Methanol was the best solvent to extract antifungal compounds. Minimum inhibitory concentration of methanol extract of tobacco, catmint, thyme, fennel, badrashbi and hyssop were equal to 1.5, 1.5, 2, 3, 3, and 2.5 mg.ml-1, respectively.