Antifungal properties of some selected plant extracts against leaf blight (Alternaria alternata) in tomato

A study was carried out under laboratory conditions during 2013–14 to evaluate the antifungal property of five different plantson leaf blight of tomato, Alternaria alternata. Aqueous and ethanolic leaf extracts of X. strumarium, Clerodendrum viscosum, Allium sativum, Polyalthia longifolia and D. stramonium showed less activity than the leaf extracts made in ethyl acetate. In antifungal assay agar of A. sativum, leaf extract (ethyl acetate) showed 100% inhibition of radial mycelial growth against A. alternata. Ethyl acetate extracts of X. strumarium, C. viscosum, P. longifolia and D. stramonium also showed antifungal growth inhibitory activity of A. alternata (inhibition 57.7, 75.5, 73.3 and 62.2%, respectively). Benzene was the best solvent for extraction of the antifungal properties among the five plants tested. Bioassay studies of bavistin against A. alternata showed minimum inhibitory concentration of 3 mg/ml. X. strumarium plant extracts tested against the pathogen have shown one distinct antifungal zone at R_f 0.85. The disease index was reduced to 1.2 when plants were sprayed with X. strumarium.