Antifungal activity of Aloe vera pulp against plant pathogenic fungi

The leaf pulp of Aloe vera Tourn. ex Linn., designated as the gel, and the bitter, yellow liquid fraction have been tested against pathogens (bacteria and fungi) affecting human and plants. However, their activity for fungal control in commercial industrial crops has not been determined. Thus, researchers at Mexico carried out studies to evaluate the inhibitory effect of Aloe pulp and liquid fraction on the mycelial growth of three phytopathogenic fungi and to determine the extract concentrations that can inhibit mycelial development. A. vera leaves were cut from plants grown under greenhouse conditions at the University Antonio Narro, disinfected with sodium hypochlorite and separated in two groups. In the first group, the pulp was manually scraped out; in the second, a laboratory roll processor was used for the pulp and liquid fraction separation. Both types of extracts were pasteurized. Antifungal activity of pulp and liquid fraction was evaluated on the mycellium development of Rhizoctonia solani, Fusarium oxysporum and Colletotrichum coccodes that were isolated from a potato crop by the hyphae point and monosporic techniques. Fungal plugs 0.4mm in diameter were placed in petri dishes with a potato–dextrose–agar (PDA) culture media and treated with various concentrations of pulp or liquid fraction. The cultures were incubated at 24±2°C and the radial growth of mycelia measured daily for 7 days. The antifungal effect was measured under a totally random design with four replications. The results obtained in this work indicate antifungal properties of A. vera pulp against F. oxysporum and the liquid fraction against R. solani, F. oxysporum and C. coccodes pathogens. The liquid fraction shows a broader range of antifungal activity than the pulp. It controlled the three pathogens, whereas the pulp inhibited only F. oxysporum. No difference was found between the manually or mechanically extracted pulps. Therefore, the commercial extraction (mechanical) method is adequate for pulp and liquid fraction production. A. vera pulp and liquid fraction may be an attractive alternative for the use of a natural product for control of fungi that attack commercial crops, avoiding chemical fungicides application [Jasso de Rodríguez D, Hernández-Castillo D, RodríguezGarcía R and Angulo-Sánchez JL, Antifungal activity in vitro of Aloe vera pulp and liquid fraction against plant pathogenic fungi, Ind Crops Prod, 2005, 21(1), 81-87].