Esca of Grapevine : A Disease Complex or a Complex of Diseases

Over the last few years research on esca has led to considerable progress in our understanding of the aetiology, epidemiology and physiology of the disease and revealed its complexity. On the basis of the available information, esca can be considered: 1. a disease complex, in the sense that several interacting factors and microorganisms concur to produce the overall syndrome; 2. a complex of at least two distinct diseases: ‘white rot’ caused by Fomitiporia punctata or other wood-rotting fungi, and brown wood-streaking and gummosis, caused by one or more species of Phaeoacremonium infecting the woody tissue; 3. a real hadromycosis induced by one or more species of Phaeoacremonium or related genera, which in mature or old grapevines is further complicated by the white rot caused by F. punctata. Research has also shown that different syndromes are produced depending on the origin of the infections, the prevalence of the associated fungi and the order in which they become active, and environmental factors. Five syndromes can be distinguished: 1. “brown wood streaking” (Petri, 1912). This affects rooted cuttings, rootstocks, and grafted or mother plants and is caused by species of Phaeoacremonium or related genera, often without external symptoms; 2. “Petri grapevine decline”. This name has been proposed to designate a decline of young grapevines known under various local names (‘black goo’, ‘slow dieback’, ‘Phaeoacremonium grapevine decline’), which occurs when propagation material or young grapevines are infected, again by species of Phaeoacremonium or related genera; 3. “young esca”. This syndrome, which Petri thought would evolve in ‘esca proper’, is characterised by black or brown wood-streaking and xylem gummosis in actively growing grapevines, with or without external symptoms. It is also caused by species of Phaeoacremonium or related genera, like the brown wood-streaking of point 1 above; 4. “white rot”. When infection is through wounds and solely or mainly by F. punctata or other wood-rotting basidiomycetes, it is characterised by wood rot, which may or may not be accompanied by external (leaf and fruit) symptoms; 5. “esca proper”. This occurs when white rot develops in the trunks of mature or old vines together with, or after, the development of brown wood-streaking. This, the full-fledged esca syndrome, is caused by the combined or successive action of one or more species of Phaeoacremonium, occasionally accompanied by other fungi, and F. punctata

Infection of Grapevines by Some Fungi Associated with Esca. I. «Fomitiporia punctata» as a Wood-Rot Inducer

Inoculation experiments with three strains of Fomitiporia punctata on grapevine cv. Sangiovese and on grafted ‘Italia’ rootstocks were carried out in southern Italy in 1992-1993. Inoculations were performed on fresh wounds made on the spurs, branches and trunks of vines showing no symptoms of esca. The fungus developed in the discoloured wood around the inoculation site, and caused white rot within two years. No symptoms were induced on foliage or fruit of the infected vines, nor was there any significant difference in virulence of the strains of F. punctata. After 2 years, re-isolation of F. punctata from the diseased woody tissues was successful, whereas no other species of fungi suspected to act as a “precursor” of wood decay were isolated. In 1999, further experiments were carried out with one strain of F. punctata on standing vines cv. Italia and Matilde free of any sign of wood deterioration. The development of internal symptoms was recorded monthly. The results indicated that the cv. Matilde was less susceptible than the cv. Italia. The first signs of spongy wood decay appeared 6 months after inoculation on both cultivars. F. punctata was re-isolated from the infected vines, whereas no species of Phaeoacremonium or other wood-decaying fungi were isolated from either inoculated or non-inoculated vines. These findings suggest that F. punctata behaves as a primary pathogen, being able to cause wood deterioration and spongy decay both on adult and young grapevines in a relatively short time, without the prior or concurrent action of other fungi

Phytopathologia Mediterranea: 50 years of plant pathology communication for the Mediterranean region

Celebrating the 50th anniversary of Phytopathologia Mediterranea foundation

Immuno-Assessment of «Pseudomonas syringae» Lipodepsipeptides (Syringomycins and Syringopeptins)

Following a previous work on the immunological detection of syringopeptins (SPs), polyclonal antibodies with a high specificity for syringomycins (SRs) were raised in rabbits and purified. Assayed in a competitive ELISA, the most common forms of SR, i.e. SR-E and SR-G, were recognised with a detection limit of 0.1 mg per well, whereas other structurally related bacterial lipodepsipeptides (LDP), such as SPs, pseudomycins (PSs) and syringotoxins (STs) were not recognised. The immuno-assay (competitive ELISA) method developed in this work is about 100 times more sensitive than the current chromatographic (HPLC) method and requires no previous extraction of the toxin. The production of LDP in culture by strains of three pathovars of Pseudomonas syringae (pv. aptata, pv. lachrymans and pv. syringae) was found to range from 0.026 to 0.055 mg ml-1 for SRs and from 0.02 to 0.06 mg ml-1 for SPs. Both the concentration of LDP in aqueous extracts from zucchini cotyledons infected by P. syringae pv. lachrymans and the severity of symptoms were shown to increase progressively after infection. The immunologically estimated concentration of SRs in the infected cotyledons averaged 0.22 mg g-1 f wt after 12 hours, and 0.39 mg g-1 after 4 days. The corresponding values for SPs were 0.11 and 0.37 mg g-1. In a recovery experiment, solutions of pure toxins (0.22 mg SR-E and 0.14 mg SP25A g-1 f wt) were injected in healthy cotyledons. After 2 days, overestimation due to toxin complexing in planta was of 10% for (SR-E) and 40% for (SP25A). Applying these percentages to the values estimated for infected cotyledons, the net concentrations were as follows: 12 h after inoculation: 0.20 (SRs) and 0.07 (SPs) mg g-1 f wt; four days after inoculation: 0.35 (SRs) and 0.22 (SPs) mg g-1 f wt. The values obtained with aqueous extracts from infected plants are relatively high if compared to the figures of the in vitro experiments. It is assumed that the high reactivity of ELISA to the immune-LDP-related compounds present in the water extracts from infected plants is due to the presence of high molecular weight LDP complexes having a cross-reactivity with antibodies substantially higher than that of free toxins

Effects on Plants of Metabolites Produced in Culture by «Phaeoacremonium chlamydosporum», «P. Aleophilum» and «Fomitiporia punctata»

Several phytotoxic metabolites were extracted and purified from culture filtrates of Phaeoacremonium chlamydosporum, P. aleophilum and Fomitiporia punctata, three fungi associated with esca of grapevine. Those identified and characterised so far were a-glucans of various molecular weight (pullulans) produced by both species of Phaeoacremonium, and two naphthalenone pentaketides (scytalone and isosclerone) produced by P. aleophilum. Absorbed at very low doses by detached leaves of grapevine or injected into the woody tissue of shoots and branches of standing grapevines, these metabolites produced foliar symptoms similar to those shown by the esca-affected vines. The same results were obtained with preparations of pullulan extracted from the discoloured woody tissue of a grapevine infected with P. chlamydosporum, and with samples of commercial pullulan

Molecular analysis of <i>"Fomitiporia mediterranea"</i> isolates from esca-affected grapevines in Southern Italy

Four Fomitiporia isolates representative of a collection of about 300 isolates from esca-affected grapevines in southern Italy (Apulia, Campania and Abruzzo) were examined by molecular methods. The DNA of each isolate was analysed by means of polymerase chain reaction (PCR amplification) using ITS5 and ITS4 primers. An amplification product of 740 bp was obtained from all isolates. The denaturated products had the same migration pattern when analysed by single-strand conformation polymorphism. The PCR fragments that included the ribosomal ITS1-5.8S-ITS2 region were sequenced. In order to ascertain the taxonomic identity of the isolates, the ITS sequences were compared with those of Fomitiporia mediterranea, F. punctata and F. robusta deposited in the GenBank. The ITS sequences of the isolates were uniform and homologous with those of the type culture of Fomitiporia mediterranea M. Fischer, to which the southern Italian isolates were compared

Phytotoxins Produced By Species of Seiridium Causing Canker Disease of Cypress .3. Seiricuprolide, A New Phytotoxic Macrolide From A Strain of Seiridium-cupressi Infecting Cypress

A strain of Seiridium cupressi, a fungus causing a canker disease of cypress (Cupressus sempervirens) in Greece, produces several phytotoxins in culture. Two of them were identified as seiridin and iso-seiridin, the butenolides previously isolated from another cypress pathogen, S. cardinale. A third phytotoxin, which is present in small amounts in the culture filtrates of S. cupressi and is not produced by S. cardinale, was identified as a new macrolide which we have called seiricuprolide. Its structure was established by spectroscopic analysis of the metabolite and of some key derivatives

New Phytotoxic Butenolides Produced By Seiridium-cardinale, the Pathogen of Cypress Canker Disease

Two new butenolides, seiridin andiso-seiridin, were isolated from culture filtrates ofSeiridium cardinale, the pathogen of cypress canker, a destructive disease ofCupressus and relatedConiferae These metabolites were characterized as 3-methyl-4-(2-hydroxyheptyl)-2(5H)-furanone and its 4-(3-hydroxyheptyl) isomer, respectively. Chlorotic, and necrotic symptoms were produced on leaves of either host or non-host test plants by absorption of 0.3 mg/ml solutions of either compound. These also showed antibacterial activity

Immuno-assessment of Pseudomonas syringae lipodepsipeptides (syringomycins and syringopeptins)

Following a previous work on the immunological detection of syringopeptins (SPs), polyclonal antibodies with a high specificity for syringomycins (SRs) were raised in rabbits and purified. Assayed in a competitive ELISA, the most common forms of SR, i.e. SR-E and SR-G, were recognised with a detection limit of 0.1 mg per well, whereas other structurally related bacterial lipodepsipeptides (LDP), such as SPs, pseudomycins (PSs) and syringotoxins (STs) were not recognised. The immuno-assay (competitive ELISA) method developed in this work is about 100 times more sensitive than the current chromatographic (HPLC) method and requires no previous extraction of the toxin. The production of LDP in culture by strains of three pathovars of Pseudomonas syringae (pv. aptata, pv. lachrymans and pv. syringae) was found to range from 0.026 to 0.055 mg ml-1 for SRs and from 0.02 to 0.06 mg ml-1 for SPs. Both the concentration of LDP in aqueous extracts from zucchini cotyledons infected by P. syringae pv. lachrymans and the severity of symptoms were shown to increase progressively after infection. The immunologically estimated concentration of SRs in the infected cotyledons averaged 0.22 mg g-1 f wt after 12 hours, and 0.39 mg g-1 after 4 days. The corresponding values for SPs were 0.11 and 0.37 mg g-1. In a recovery experiment, solutions of pure toxins (0.22 mg SR-E and 0.14 mg SP25A g-1 f wt) were injected in healthy cotyledons. After 2 days, overestimation due to toxin complexing in planta was of 10% for (SR-E) and 40% for (SP25A). Applying these percentages to the values estimated for infected cotyledons, the net concentrations were as follows: 12 h after inoculation: 0.20 (SRs) and 0.07 (SPs) mg g-1 f wt; four days after inoculation: 0.35 (SRs) and 0.22 (SPs) mg g-1 f wt. The values obtained with aqueous extracts from infected plants are relatively high if compared to the figures of the in vitro experiments. It is assumed that the high reactivity of ELISA to the immune-LDP-related compounds present in the water extracts from infected plants is due to the presence of high molecular weight LDP complexes having a cross-reactivity with antibodies substantially higher than that of free toxins