Diseases In Vineyards Research Articles

Biological Control of Pierce's Disease in the Vineyard with Strains of Xylella fastidiosa Benign to Grapevine.

Naturally occurring strains of Xylella fastidiosa Wells et al. that were weakly virulent or aviru-lent to grapevine were inoculated into the lower internodes of Vitis vinifera L. cv. Carignane plants in the greenhouse and challenge inoculated with pathogenic strains 2 weeks later. Several strains provided some reduction in symptom development. Most effective in preventing or slowing the development of Pierce's disease in the greenhouse tests were a strain from sycamore and two from elderberry. In a 2-year test on 'Himrod' grape in the vineyard, strain Syc86-1 (from sycamore), but not strain PD-1 (from grapevine), was effective in limiting the development of Pierce's disease. In tests on new vineyard plantings of 'Flame Seedless' and 'Cabernet Sauvi-gnon', six strains of X. fastidiosa were evaluated for biological control of the natural progression of Pierce's disease. Only strain EB92-1 (from elderberry) provided good control of the disease in both Flame Seedless and Cabernet Sauvignon. Strain Syc86-1 was ineffective in these vineyard tests. Grape strain PD95-6 did lower disease severity in Flame Seedless when compared with nontreated vines, and grape strain PD91-2 delayed symptoms in Cabernet Sauvignon for 12 to 18 months. Biological control by inoculation of susceptible grapevines with benign strains of X. fastidiosa, especially strain EB92-1, appears to have the potential to control Pierce's disease in commercial vineyards in Florida and other areas where the disease occurs.

Immunology-related perturbations induced by copper and chitosan in carp (Cyprinus carpio L.).

Copper is used in treatment mixtures to control fungal diseases in vineyards. Its concentrations are relatively high in some aquatic ecosystems, and the main problem observed in this study was the antioxidant stress induced by this heavy metal. Copper toxicologic effects in aquatic organisms have prompted the demand for alternative use of low-toxicity molecules in culture treatments. Chitosan is a polymer with antifungal property similar to copper and may be an interesting biopesticide. Thus, it is necessary to investigate the potential toxicity of chitosan for aquatic animal health, either alone or in conjunction with copper. In this study, carp were exposed to two sublethal chitosan concentrations (75 and 150 mg/L) or to two sublethal copper concentrations (0.1 and 0.25 mg/L) or to a mixture of chitosan plus copper (75 mg/L and 0.1 mg/L, respectively). The results of the present study show that exposure to copper at environmentally realistic levels or to chitosan at sublethal concentrations may significantly stimulate various aspects of immune functions in carp such as nonspecific cellular immunity, represented by total immunoglobulin level, ceruloplasmin activity, and oxidative activity of phagocytes. This acute-phase inflammatory response induced separately by the two treatments was not observed, especially on phagocyte oxidative activity, when carp were exposed to the copper-chitosan mixture. This fact could be explained by a possible chelation of copper by chitosan decreasing the biodisponibility of the two products for immune cells. Thus, the immunotoxicologic impact of copper and chitosan on fish immune response would be less pronounced with the combined treatments than with separate treatments in an aquatic environment.

Activity of the new fungicide benthiavalicarb against Plasmopara viticola and its efficacy in controlling downy mildew in grapevines

Benthiavalicarb is a new fungicide active against Oomycetes fungal plant pathogens. The present study shows that benthiavalicarb is effective for controlling the Oomycete fungal pathogen Plasmopara viticola, which causes downy mildew in grapevines. The fungicide did not affect zoospore discharge from sporangia of P. viticola, but strongly inhibited zoospore encystment, cystospore germination in vitro and mycelial growth, together with sporangial production in vivo. Benthiavalicarb showed strong prophylactic and local activity in intact plants or detached leaves and low translaminar activity. The compound was not translocated from leaf to leaf in either a acropetal or basipetal direction. Benthiavalicarb applied at 1, 3 and 6 days post-inoculation protected grapevine plants against downy mildew and inhibited sporulation of the pathogen. Similar results were obtained on leaf disks if benthiavalicarb was applied up to 96 h post-inoculation. Benthiavalicarb diminished the sporulation of P. viticola when applied to established disease in the tissue. Benthiavalicarb remained active on leaves for a period up to 28 days. Two foliar applications of benthiavalicarb, 2 weeks apart, to field-grown grapevines inhibited downy mildew development and were as effective as the standard metalaxyl-Cu treatment in controlling the disease. A formulated mixture of benthiavalicarb + Folpet was similar or superior in performance to metalaxyl-Cu and the new strobilurin trifloxystrobin in controlling downy mildew. The effectiveness of benthiavalicarb makes it well suited for integration into a control programme against downy mildew disease in vineyards, and as a component to delay resistance buildup.

Protection against virus infection in tobacco plants expressing the coat protein of grapevine fanleaf nepovirus

Grapevine fanleaf nepovirus (GFLV) is responsible for the economically significant "court-noué" disease in vineyards. Its genome is made up of two single-stranded RNA molecules (RNA1 and RNA2) which direct the synthesis of polyproteins P1 and P2 respectively. A chimeric coat protein gene derived from the C-terminal part of P2 was constructed and subsequently introduced into a binary transformation vector. Transgenic Nicotiana benthamiana plants expressing the coat protein under the control of the CaMV 35S promoter were engineered by Agrobacterium tumefaciens-mediated transformation. Protection against infection with virions or viral RNA was tested in coat protein-expressing plants. A significant delay of systemic invasion was observed in transgenic plants inoculated with virus compared to control plants. This effect was also observed when plants were inoculated with viral RNA. No coat protein-mediated cross-protection was observed when transgenic plants were infected with arabis mosaic virus (ArMV), a closely related nepovirus also responsible for a "court-noué" disease.

Perspectives in neuro-ophthalmology.

<h3>Abstract</h3> Grapevine red blotch disease (GRBD) is an emerging disease caused by grapevine red blotch virus (GRBV). It is widespread in a majority of wine grape production regions in the United States and differential spread dynamics have been reported between the regions. In this study, we surveyed eight vineyard sites in southern Oregon over four years for the progression of GRBD incidence. The surveyed vineyards included five sites that were five years or older and three sites that were three years old. The disease incidence in the older blocks ranged from 2.81 to 58.78%; whereas in the younger blocks it ranged from 0.29 to 1.11%. Some of these vineyards implemented frequent disease scouting, removing, and replanting. The disease incidence in these blocks remained less than 5% over the survey period. However, in the vineyards that did not implement any roguing and replanting, the disease incidence increased by nearly 30-fold after three years. We analyzed the spatial distribution of the disease in vineyards surveyed in 2020 and found that the disease distribution is highly aggregated based on Spatial Analysis by Distance Indices (SADIE). In a separate study, we also tested the GRBV infection status of asymptomatic vines next to symptomatic vines to aid in the decision making process when roguing and replanting. Out of 410 asymptomatic vines, surrounding 41 symptomatic vines, only two tested positive for GRBV. Additionally, in 2020 and 2021, we tested the GRBV status on previously identified possible alternative host species, blackberries (<i>Rubus armeniacus</i>) and wild/feral grapes (<i>Vitis riparia</i>) collected from areas surrounding the four survey sites. We observed that GRBV was present in 10 to 70% of the wild grape samples in both years and 10% of the blackberry samples in 2020. However, the virus titer was low in blackberry samples and it was not detected in 2021 samples. These results indicate the potential importance of wild grapes as alternative hosts on GRBD incidence and spread in southern Oregon vineyards, while blackberry is unlikely to be an alternative host with epidemiological significance.