Dysfunctionality of the Xylem in Olea europaea L. Plants Associated with the Infection Process by Verticillium dahliae Kleb. Role of Phenolic Compounds in Plant Defense Mechanism

Abstract

Xylem ultrastructural modification and the possible participation of phenolic compounds in the natural defense or resistance mechanisms of olive plants infected with Verticillium dahliae Kleb. were studied. Microscopic study showed that the mycelium propagated and passed from one element to another through the pit. The formation of tyloses and aggregates contributed to obstruction of the xylem lumen. In vivo changes in the levels of these phenolic compounds in infected olive plants and their antifungal activity against Verticillium dahliae Kleb., as revealed by in vitro study, strongly suggest that they are involved in natural defense or resistance mechanisms in this plant material, the most active being quercetin and luteolin aglycons, followed by rutin, oleuropein, luteolin-7-glucoside, tyrosol, p-coumaric acid, and catechin. .

Evaluation of susceptibility of an olive progeny (Picholine x Meski) to olive leaf spot disease caused by Fusicladium oleagineum

“…Oleuropein, tyrosol, hydroxytyrosol and rutin display a fungicidal effect (Baidez et al 2007;Pereira et al 2007). The derivatives of oleuropein, like oleuropein glucoside, seems to be implied in the defence of the olive tree by inhibiting the pectinases of F. oleagineum (Graniti 1993) and by constituting a precursor of phytoalexins (Uccella 2000), extremely toxic molecules induced in response to pathogen infection (El Modafar et al 1995.…”

Scientific opinion on the pest categorisation of Verticillium dahliae Kleb

“…Conidia often become trapped at pit border membranes between vessels, where they germinate within two hours; germ tubes penetrate through the membranes to the neighbouring vessel, and more conidia are produced to repeat the process to grow restrictedly within the individual tracheae. Penetration of adjacent vessels can also occur both by germ tubes and hyphae, giving rise to more intense colonisation of the plant (Baidez et al, 2007;Klosterman et al, 2009;Jiménez-Díaz et al, 2012;Zhang et al, 2013).…”

Susceptibility of Cultivars to Biotic Stresses

“…Very little is known about biochemical and molecular mechanisms of olive resistance to the Verticillium wilt. Among investigated aspects, it seems to be very important the role of phenolic methabolism (Baidez et al, 2007;Markakis et al, 2010). Vizzarri et al (2011) investigated the susceptibility of cvs.…”