Assessment of the antifungal activity of Nicotiana glauca Graham aqueous and organic extracts against some pathogenic and antagonistic fungi

Abstract

In the present research work, Nicotiana glauca Graham was used as a potential source of biologically active compounds. The antifungal activity of leaf and flower aqueous and organic extracts (petroleum ether, chloroforme and methanol) was assessed in vitro against three phytopathogenic fungi and two antagonistic agents. These target fungi were subjected to the different types of extracts already incorporated into the Potato Dextrose Agar (PDA) medium at various concentrations. Results revealed an important antifungal activity of N. glauca leaf and flower aqueous extracts at all concentrations tested (1, 2, 3 and 4%). However, a relative difference in the extent of the response of the same fungal agent to the extracts tested was observed. In fact, Trichoderma viride was found to be more sensitive than the other target species, where the radial growth inhibition noted varied from 37.4 to 63.14% depending on aqueous extracts concentrations and the maximum inhibition was obtained with leaf aqueous extracts applied at 1 and 2% concentrations. Moreover, T. viride and Fusarium oxysporum f. sp. melonis were found to be the most sensitive to leaf and flower organic extracts as compared to the other agents. Growth of T. viride was inhibited by 33.7% in the presence of chloroform leaf extract and petroleum ether flower extracts tested at 3000 and 9000 ppm, respectively. Furthermore, the radial growth of F. oxysporum f. sp. melonis was reduced by more than 31 and 20% with leaf petroleum ether and flower chloroform extracts, respectively, applied at 9000 ppm. T. harzianum, F. oxysporum f. sp. tuberosi and F. oxysporum f. sp. lycopersici were found to be less sensitive to N. glauca organic extracts as compared to aqueous extracts. Key words: Antifungal activity, aqueous extracts, allelopathy, Nicotiana glauca Graham,Fusarium, Trichoderma and radial growth.