Carmine Amalfitano

Phenols and Stilbene Polyphenols in the Wood of Esca-Diseased Grapevines

Trans-resveratrol and e-viniferin, already described as stress metabolites produced by the leaves of Vitis vinifera in response to fungal infection, UV irradiation, and incubation by chemicals, have been detected in the wood of healthy as well as in the brown-red wood of esca-diseased grapevines. Brown-red wood is considered an initial symptom of esca in grapevine. Resveratrol was the predominant component although e-viniferin was also accumulated in appreciable quantities. The biological significance of the production of resveratrol and e-viniferin is discussed.

Chemical and spectroscopic characteristics of the wood of Vitis vinifera cv. Sangiovese affected by esca disease.

Chemical and spectroscopic analyses ((13)C cross-polarization-magic angle spinning NMR and attenuated total reflection Fourier transform infrared spectroscopies) were carried out on the wood of Vitis vinifera cv. Sangiovese with brown-red discoloration and black streaks caused by esca disease. The analyses of the brown-red wood revealed the destruction of hemicelluloses and noncrystalline cellulose as well as modifications in the pectic and ligninic wood fractions. The pectic fraction consisted of carbohydrates associated with polyphenols. The lignin fraction exhibited only a few changes in the aromatic systems and a partial demethylation, and it appeared to be associated with condensed phenolic components probably arising from response polyphenols. The degradation of hemicelluloses and noncrystalline cellulose in brown-red wood, where the pathogens Phaeoacremonium aleophilum and Phaeomoniella chlamydospora prevail with respect to the other fungus Fomitiporia mediterranea, was consistent with reports on the degradative activity of such fungi in vitro carried out on model substrates. The observed alterations could also be attributed to the radical oxidation process caused by the oxidative response of defense itself triggered by infection, as suggested by the accumulation of postinfectional compounds. The analyses of wood tissue with black streaks showed less marked deterioration; here, an increase in pectic and phenolic substances, which probably accumulate in the xylem vessels as a response to the infection, was observed.

Inhibition of Species of the Aspergillus Section Nigri and Ochratoxin A Production in Grapes by Fusapyrone

ABSTRACT Fusapyrone (FP), an antifungal natural compound, was tested against the three main ochratoxigenic species of the Aspergillus section Nigri. The MICs at 24 h were 6.0, 11.6, and 9.9 μg/ml for Aspergillus carbonarius, Aspergillus tubingensis, and Aspergillus niger, respectively. Strong inhibition of growth and morphological changes were still observed at half the MIC after 7 days. The application of a 100 μg/ml FP solution in a laboratory assay on artificially inoculated grapes resulted in a significant reduction (up to 6 orders of magnitude) of A. carbonarius CFU counts. Dramatic reductions of the ochratoxin A (OTA) content, compared to the content of the positive control (average amount of OTA, 112.5 ng/g of grape; three experiments), were obtained with the application of either 100 or 50 μg/ml of FP (0.6 or 5.1 ng/g of grape, respectively).

High performance liquid chromatography for the analysis of fusapyrone and deoxyfusapyrone, two antifungal α-pyrones from Fusarium semitectum

A simple, very sensitive and rapid HPLC method was developed for the simultaneous quantitative analysis of both fusapyrone (FP) and deoxyfusapyrone (DFP), the two antifungal 3-substituted-4-hydroxy-6-alkyl-2-pyrones isolated from rice culture of Fusarium semitectum, in crude extracts. Such method was optimized on C-18 reverse phase column, using the isolated metabolites as standards, with a sequence of linear elution steps with a MeOH-H(2)O mixture and using an ultraviolet detector fixed at 285 nm, where both alpha-pyrones showed a characteristic absorption maximum. This method was used to quantify the bioactive metabolites in crude organic extracts from two F. semitectum strains. The recovery of FP and DFP was measured in a crude extract from a poor metabolite producer F. semitectum strain. The recovery values ranged from 84% to 99% for FP and from 99% to 101% for DFP, indicating that the method was close to quantitative recovery. Furthermore, an efficient medium pressure column chromatography and TLC combined method was developed for the isolation and purification of FP and DFP from fungal culture extracts.

Polyphenol distribution in plant organs of tomato introgression lines.

The content of total polyphenols, chlorogenic, caffeic (CaA) and ferulic acids, and rutin, was investigated in plant organs of three introgression lines (IL7-3, IL10-1 and IL12-4) of Solanum pennellii in Solanum lycopersicum cv M82 and compared with that of cropped parental. Such study aims to evidence factors associated to the introgressions that can affect polyphenol distribution in plant. Among genotypes few differences in polyphenols were recorded on fresh weight basis. IL7-3 showed higher total polyphenols in fruits and lower rutin in leaves than the other genotypes. IL12-4 showed an increasing trend of total polyphenol concentration in fresh vegetative organs; however, this seems to depend on the lower water content rather than on a higher polyphenol biosynthesis in the genotype. IL10-1 sowed higher CaA and lignin contents in leaves. Such differences agree with the morphological and physiological traits of the genotypes.

BTH and BABA induce resistance in pea against rust (Uromyces pisi) involving differential phytoalexin accumulation

AbstractMain ConclusionSystemic acquired resistance elicitors, BTH and BABA, reduce rust penetration in pea through phytoalexins pathway but differing in their mode of action. It has been previously shown that rust (Uromyces pisi) infection can be reduced in pea (Pisum sativum) by exogenous applications of systemic acquired resistance elicitors such as BTH and BABA. This protection is known to be related with the induction of the phenolic pathway but the particular metabolites involved have not been determined yet. In this work, we tackled the changes induced in phytoalexin content by BTH and BABA treatments in the context of the resistance responses to pea rust. Detailed analysis through high-performance liquid chromatography (HPLC) showed qualitative and quantitative differences in the content, as well as in the distribution of phytoalexins. Thus, following BTH treatment, we observed an increase in scopoletin, pisatin and medicarpin contents in all, excreted, soluble and cell wall-bound fraction. This suggests fungal growth impairment by both direct toxic effect as well as plant cell wall reinforcement. The response mediated by BTH was genotype-dependent, since coumarin accumulation was observed only in the resistant genotype whereas treatment by BABA primed phytoalexin accumulation in both genotypes equally. Exogenous application to the leaves of scopoletin, medicarpin and pisatin lead to a reduction of the different fungal growth stages, confirming a role for these phytoalexins in BTH- and BABA-induced resistance against U. pisi hampering pre- and postpenetration fungal stages.

Foliar treatment of esca-proper affected vines with nutrients and bioactivators

Foliar treatment with nutrients and bioactivators was carried out in two vineyards affected with esca proper in 2004 and 2005. Changes in the foliar symptoms and in the quality of berries without lesions from treated symptomatic vines were assessed. Treated vines unexpectedly had a higher incidence and a greater severity of symptomatic leaves than untreated plants, most likely because physiological processes were stimulated by the treatments, possibly also because treatments facilitated the movement of toxins produced by the wood fungi of esca. However it cannot be excluded that the increase in foliar symptoms was due to the forced nutrition causing an imbalance between the various elements, and altering the mechanisms that vines use for the remission of foliar symptoms. This supposition seemed corroborated by the observation that treated vines diseased with esca proper had a weaker defense response than untreated diseased vines, and that treated diseased vines had lower levels of nitrogen and microelements, which are respectively involved in osmoregulation and as cofactors of enzymes involved in the defense response of the plant. The main quality parameters of berries without lesions from treated and untreated symptomatic vines were very similar.