Data di Pubblicazione:
2012
Citazione:
EFFECT OF SAR INDUCERS ON GRAPE SECONDARY METABOLITES / S. Vitalini ; tutor: F. Faoro, M. Iriti ; coordinatore: D. Bassi. Universita' degli Studi di Milano, 2012 Jan 25. 24. ciclo, Anno Accademico 2011. [10.13130/vitalini-sara_phd2012-01-25].
Abstract:
Fungicide application is now the most efficacious method for controlling plant diseases caused by oomycetes and fungi. As legislation is limiting and reducing their use, it is strongly stimulating studies for the identification of additional and environmentally friendly approaches in the control of their associated diseases. Among these, systemic acquired resistance (SAR) offers the prospect of long-lasting, broad-spectrum disease control through activation of the resistance defence machinery of the plant itself. Plant activators are products employed in crop protection able to elicit SAR. Therefore, they may trigger the plant own defence response against pathogen attacks, mainly stimulating mechanisms such as the biosynthesis of phytoalexins, plant secondary metabolites with a broad spectrum biological activity. In this study, two plant defence inducers, benzothiadiazole (BTH) and chitosan (CHT), deserving particular attention because of their efficacy and low toxicity, have been used. CHT is a natural and low-cost polymer (from the waste products of the crustacean carapace), obtained by chitin deacetylation. Its effectiveness is higher when molecular weight is between 10 and 100 kD and the deacetylation degree range is from 80 to 90 percent. BTH [benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester] is a synthetic compound and a functional analogue of salicylic acid, a plant hormone-like compound deeply involved in resistance against pathogens. Two different phytoiatric campaigns were planned, in 2009 and 2010, on two red grapevine (Vitis vinifera L.) varieties cultivated in experimental vineyards located at distinct sites: Groppello, an autochthonous cultivar of Lombardia, at Raffa di Puegnago (Brescia), and Merlot at Conegliano Veneto (Treviso). Open field treatments carried out on Groppello grapevines were: i) 0.03% (w/v) CHT (76 kDa molecular weight and 85% deacetylation degree), ii) 0.03% CHT in combination with 150 g hL-1 copper hydroxide (CHT/Cu) and iii) 0.3 mM BTH; whereas, on Merlot, besides CHT and CHT/Cu, BTH were replaced by 300 g hL-1 potassium phosphites. Untreated vines were used as negative control, while plants treated with conventional fungicides (penconazole and methyldinocap) were the positive control. In both field surveys, the trial was set up as a complete randomized block design in 4 replications, with 10 vines (a parcel) per treatment in each block. Plants were sprayed approximately every 10 days, according to the meteorological conditions, from the beginning of grape susceptibility to fungal diseases until the complete véraison. The phytosanitary status of vineyards was assessed weekly on leaves and bunches, by visual inspections, though both sites were not particularly predisposed to severe fungal or other epidemics. The epidemiological evaluations were performed on bunches alone and infection indexes were calculated. All the treatments were effective in controlling fungal infections (downy mildew, Plasmopara viticola and powdery mildew, Erysiphe necator), in terms of disease incidence (I %), disease severity (S %) and infection degree (ID %), though these indexes were low in untreated control grapevines, particularly in 2010. Sampling was scheduled at two phenological phases: pre-véraison and 100% véraison; bunches were randomly collected from plants during the morning and stored at -20 °C until analyses. Berry tissues were separated into skin, flesh and seeds, powdered and extracted. Then, extracts were tested to evaluate their melatonin levels [by ultra performance liquid chromatography (UPLC)-MS/MS], total polyphenols (TP, by Folin-Ciocalteau assay) and antiradical activity [by DPPH, 2,2-diphenyl-1-pycryl hydrazyl and ABTS, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assay].
Tipologia IRIS:
Tesi di dottorato
Keywords:
systemic acquired resistance ; plant activators ; grapevine fungal diseases ; grapes ; wine ; polyphenols ; melatonin ; antiradical activity
Elenco autori:
S. Vitalini
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