1 INTRODUCTION
“Esca” is one of the oldest diseases of grapevine (Vitis vinifera L.) known wherever grapes are grown, characterised by wood decay, “apoplexy” (sudden wilting of the vine) and leaf “tiger-stripes” (Mugnai, Graniti & Surico, 1999; Graniti, Surico & Mugnai, 2000; Surico, 2009). The most recent proposal considers “Esca” as a complex of different diseases overlapping in the same vine or developing the vine life. Following this tendency, the old “Esca” is a combination of five diseases: brown wood streaking, Petri disease, grapevine leaf stripe disease, white rot and Esca proper. Brown wood streaking affects vines in the nursery. Petri disease interferes with new vine plantations and coupled vascular discolouration with chlorosis and decline. The grapevine leaf stripe diseases involve on young and adult vines, with wood streaking or/and wood decay. Esca proper is referred to adult vines with the simultaneous presence of white rot, dark wood streaking and leaf “tiger-stripes” (Graniti, Surico & Mugnai, 2000; Surico, 2009; Mondello et al., 2018). Different fungi are involved in these diseases. Species of Fomitiporia (F.mediterranea M. Fisch. mainly in Europe) are associated with wood decay of white rot and Esca proper. Phaeoacremonium minimum (Tul. & C. Tul.) Gramaje, L. Mostert & Crous (≡ Pm. aleophilum W. Gams, P.W. Crous, M.J. Wingf. & L. Mugnai) and the anamorphicPhaeomoniella chlamydospora (W. Gams, P.W. Crous, M.J. Wingf. & L. Mugnai) P.W. Crous & W. Gams, are the etiological agents of brown wood streaking and Petri disease (Mugnai, Graniti & Surico,1999; Surico, 2009; Mondello et al., 2018). Other Phaeoacremonium andCadophora species have been isolated from wood of grapevines affected by “Esca complex” diseases (Surico, 2009; Moreno-Sanz et al., 2013; Mondello et al., 2018; Elena et al., 2018; Jayawardena et al., 2018).
The leaf stripe symptoms are considered as the result of cultivar susceptibility, age of the vines, microorganisms involved and pedoclimatic conditions (Graniti, Surico & Mugnai, 2000). The substances originate in the discoloured woody tissues of the trunk and branches, moved to the leaves in the transpiration stream and are associated to leaf “tiger-stripes” development. These substances can be reaction products of the wood, phytotoxic metabolites excreted by “Esca complex” fungi, or their combination (Bruno, Sparapano & Graniti, 2007). Pa. chlamydospora and Pm. minimum produce two naphthalenone pentaketides (scytalone and isosclerone) and exopolysaccharides including the α-glucan named pullulan (Evidente et al., 2000; Tabacchi et al., 2000; Bruno & Sparapano 2006a, 2006b, 2007). Macro and micronutrient have a role in “Esca complex” symptom progression (Calzarano et al., 2006).
Stomata closure and change of the photosynthetic apparatuses were associated with grapevine leaf stripe occurrence (Petit et al., 2006; Magnin-Robert, 2011). The presence of less dense cytoplasm, plastids with small starch grains, underdeveloped grana and elongated thylakoids describe grapevine leaves before developing “tiger-stripes” (Lima et al., 2010; Fontaine et al., 2016). Glutathione pool, PR-proteins and phenolic compounds are also affected (Calzarano et al., 2006; Magnin-Robert, 2011; Lima et al., 2010; Fontaine et al., 2016; Valtaud et al., 2011; Lambert, 2013). Xylem dysfunction also influenced water transport and leaf water potential (Bruno, Sparapano & Graniti, 2007; Fontaine et al., 2016). NMR data suggests an increment of phenylpropanoid compounds production and a decrement of glucose and fructose content in “Esca” diseased vines (Lima et al., 2010).
In the present paper, the goal is an increase of knowledge on the variations of some physiological features of bleeding xylem sap and leaves of grapevine cv Italia. However, this study gives a great deal of attention to the differences in hydrogen peroxide, lipid peroxidation and antioxidant defence responses associated with the ascorbate-glutathione cycle between health and diseased vines.