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.