86,542 research outputs found
Nutritional status of vines afected with esca proper
No full textA vineyard of the cv. Trebbiano d’Abruzzo located in Abruzzo, Italy, was monitored for more than ten years to distinguish healthy vines not only from vines with the visual leaf symptoms of esca, but also from those vines that were esca-infected but did not produce any visual symptoms for one or more growing seasons. In the period 2004–2006, leaves and berries were collected at four phenological growth stages from three groups of vines: healthy vines, infected vines showing esca symptoms, and infected vines that did not show symptoms. The macro and micro-elements of the leaves and berries, and the quality parameters of the must were determined. Esca did not seem to affect nutrient uptake in the vines. Nevertheless there were some differences in the nutrient levels of the leaves between healthy and diseased vines consistent with the degradation of the leaf blade caused by esca. Berries from symptomatic vines were less ripe at the time of harvesting and therefore had higher levels of mineral elements. These berries also had higher levels of nitrogen, which are thought to be associated with the defence response of diseased vines to esca, as are higher levels of iron in the leaves of diseased vines. The study confirmed earlier findings that fruit composition did not differ greatly between healthy and diseased-but-asymptomatic vines. In the three-year study period there were differences in the incidence of leaf symptoms and differences in nutrient levels attributable to fertiliser applications and rainfall. These differences suggested that the amount of mineral nutrients affected the onset of esca symptoms: a higher availability of nutrients in a growing season increased the proportion of diseased vines with symptoms and lowered the proportion of diseased vines without symptoms, whereas in a growing season with the lower levels of water and potassium, the yield was reduced, but this was accompanied by an increase in the proportion of diseased vines without symptoms. It is suggested that a higher availability of nutrients for diseased vines lowers the resistance of these vines and, by improving the nutrition not only of the vines themselves but also of the esca fungi, increase fungal virulence, as a result of which there is a greater incidence of diseased vines showing leaf symptoms
Trans-resveratrol and leaf symptom expression in Esca of grapevine
No full textEsca of grapevine is a serious disease which in some aspects is still lacking full understanding, including the nature of foliar symptoms. Leaves collected at different phenological growth stage from esca symptomatic grapevines cv. Trebbiano d'Abruzzo showed the presence of higher concentrations of trans-resveratrol, the major stilbene produced in grapevine, compared to leaves from healthy plants. The increased levels of trans-resveratrol were supposed to be associated with the host-plant defence response, thought it also raises new questions on a possible role of the stilbene in the foliar symptom development. In 2009, symptomatic leaves were collected from the above mentioned grapevines and were divided into 4 classes calculating symptom severity as the percentage of chlorosis and necrosis on the total leaf area. For each class, leaves were collected at pre-bunch closure, post-veraison and harvest, and the level of trans-resveratrol was determined. The results showed higher concentrations of trans-resveratrol in symptomatic leaves collected at pre-bunch closure compared to what observed at the other growth stages. These results are in agreement with our previous findings and the stronger response of leaves might be correlated with the leaf functioning at the different phenological growth stages; moreover, the increasing of concentrations of trans-resveratrol with the increasing of the severity of leaf symptoms seems to exclude an involvement of the stilbene in the formation of symptoms. Further investigations on cut leaves inoculated with pathogen culture filtrates and/or trans-resveratrol may lead to a better understanding of the relationship between the stilbene and the foliar symptom expression.[...
Effect of Different Foliar Fertilizer Applications on Esca Disease of Grapevine: Symptom Expression and Nutrient Content in the Leaf and Composition of the Berry
No full textEsca disease, the most common grapevine wood disease in Europe, causes yield losses correlated with the foliar symptoms’ expression. In two vineyards located in the Abruzzo Region of Italy, each of which were investigated for esca symptoms after 1994, different applications of macro- and microelements were performed in two consecutive growing seasons. The main aim of the work consisted of verifying the effects of the fertilizer applications on the foliar symptoms’ expression, in order to deepen knowledge of the nature of the symptom, which is still unclear. For each treatment, in each year, the leaf content of macro- and microelements and the composition of berries and musts were assessed. The effects of these applications on vegetative growth and yield quantity were also verified. The trials were carried out on symptomatic, asymptomatic and
apparently healthy vines. All applications, in particular those with microelements, increased the foliar symptoms’ expression, and a greater vegetative growth was detected only in vines treated with NPK fertilizers. The symptoms’ increase was always associated in the leaf with a decrease of calcium, and to a lesser extent, magnesium, reinforcing the hypothesis of the plant’s hypersensitive reaction in the development of foliar symptoms, given the role of calcium in the defense response. The vineyards were in nutritional balance regardless of the fertilizer applications. The general increase in foliar symptoms and the decrease in sugars in the musts of asymptomatic treated vines underlined the importance of the vegetative-productive balance, in Esca infected vineyards especially, in order to limit the symptoms’ expression and the decrease in yield
First evaluations on the relationship between esca symptoms and trans-resveratrol in the leaf.
No full textAbstract: The formation of foliar symptoms of esca in grapevine has not been clarified yet; probably, symptoms are associated with toxins released by vascular pathogens involved in the disease, and translocated to the leaf by the transpiration stream. Long term investigations recently conducted in Central Italy on two vineyards cv. "Trebbiano d'Abruzzo" infected with esca proper, showed significantly highest levels of trans-resveratrol in symptomatic leaves at the pre-bunch closure. Further investigations carried out on symptomatic leaves with different symptom severity revealed increasing levels of trans-resveratrol with the severity of symptoms on leaf. These results seem to show that trans-resveratrol is not able to stop the development of foliar symptoms. Moreover, cut leaves immersed with their petioles in Phaeomoniella chlamydospora cultural filtrates combined with progressive doses of trans-resveratrol did not reveal any visible effect of the stilbene. After pre-bunch physiological changes leading to berry maturation and carbohydrate accumulation occurred. In this period the leaf showed a drastic decrease of trans-resveratrol levels in symptomatic leaves, and low levels of the stilbene were noticed until veraison. Probably the strong decline of trans-resveratrol can be interpreted as a proof of a different response of the plant to the disease, in the time in which foliar symptoms spread up to harvest. Further studies are undergoing. [...
Effects of fosetyl Al treatments on grapevine plants in esca management
No full textEsca is the most severe and widespread grapevine wood disease. Although foliar symptom expression is not correlated with vine wood deterioration because of the intermittent nature of esca leaf symptom, the loss of production is associated with foliar symptom expression being diseased asymptomatic vines able to produce grapes with similar characteristics to grapes from healthy vines. Foliar symptoms seem to be associated with transport of toxins from infected wood to leaves. A reduction in esca symptom severity was observed in many-year trials applying commercial formulations of fosetyl Al either before or soon after the appearance of esca in vineyards properly managed and following the plan for downy mildew control. Moreover, a reduction of the average length of internal necrosis following inoculations with vascular esca pathogens and treated by fosetyl Al was noticed in potted vines. Investigations were carried out in order to explain the activity of fosetyl Al towards esca and associated pathogens. Physiological parameters of potted plants were measured: net photosynthetic rates of infected untreated plants were depressed by 20-50% for 24-60 hours after treatment compared to infected untreated ones. Foliar total proteins were extracted and tested by spectrophotometric analyses. In infected treated leaves chitobiosidase and glucosaminidase activities increased from 3 to 9 days after treatment, glucanase activity was enhanced at the third day and lypoxigenase activity increased over the time at pH 6.5, compared to untreated leaves. No differences in trans-resveratrol and ε-viniferin contents were found in the wood of treated and untreated vines. Results were discussed
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