Abstract
Verticillium wilt (caused by Verticillium dahliae Kleb.) is an important disease affecting olive (Olea europaea L.) production. Effective control of this disease relies on integrated management strategies. In vitro antifungal activity of two hydroxytyrosol (HTyr) enriched extracts (HTE1 and HTE2) obtained from olive mill waste products (OMWP) was assessed against V. dahliae. Inhibitory effects of pure HTyr as a standard, and HTE1 and HTE2 at different concentrations, were evaluated on mycelium growth and conidium germination of V. dahliae. Chemical characterization of HTE1 and HTE2 allowed identification and quantification of HTyr as the main constituent in both extracts along with other low molecular weight phenols. HTE1 showed a higher inhibitory activity in both growth and conidium germination of V. dahliae. At the tested concentrations, low antifungal effects of HTyr were observed. After 3 d, 1 mg mL-1 of HTE1 gave greater inhibition of mycelium growth than HTE2 or HTyr. After 24 h, HTE1 gave 55% inhibition of conidium germination, and HTyr and HTE2 both gave 37% inhibition. This study has demonstrated that phenolic compounds derived from OMWP have antifungal activity against V. dahliae, indicating the potential of these compounds for eco-friendly control of Verticillium wilt.
Highlights
Verticillium wilt, caused by Verticillium dahliae, severely affects olive trees (Olea europaea L.), causing economic losses due to plant death (Jiménez-Díaz et al, 1998; López-Escudero and Mercado-Blanco, 2011)
The present study evaluated the effectiveness of two HTyr-enriched extracts from olive mill waste products (OMWP) against V. dahlia using pure HTyr as standard
The main compound found was HTyr at 32.83 mg g-1, representing the 64.7% w/w of the total phenols (50.7 mg g-1). Minor components in this extract were verbascoside (12.9 mg g-1, 25.4% w/w), tyrosol, gallic acid and verbascoside derivatives, which in total constituted the 9.6% w/w of total phenols. This is the first description of HTE2
Summary
Verticillium wilt, caused by Verticillium dahliae, severely affects olive trees (Olea europaea L.), causing economic losses due to plant death (Jiménez-Díaz et al, 1998; López-Escudero and Mercado-Blanco, 2011). The soilborne fungus is considered one of the most serious threats to olive fruit and Mounira Inas Drais et alii oil production, and the disease is widely distributed in all Mediterranean olive-growing regions (Jiménez-Díaz et al, 2012). Verticillium dahliae infects host plants through their roots, and colonizes vascular systems, blocking water flow and eventually inducing wilt symptoms (Van Alfen, 1989). This damage results in significant reductions of leaf transpiration, which lead to leaf chlorosis and defoliation. Severe attacks cause trees to eventually die
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