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Black Rot is a grapevine disease caused by the ascomycete Phyllosticta ampelicida. Neglected so far, this is developing into a pertinent problem in organic viticulture as resistant varieties are still lacking. Here, we follow cellular details of the infection process in the susceptible vinifera variety Müller‐Thurgau and screen the ancestral European wild grapevine (V. vinifera sylvestris) for resistance to Black Rot.Using a standardized infection assay, we follow fungal development using LTSEM and quantify key stages on different hosts using fluorescence microscopy.There is considerable variation in susceptibility, which is associated with more rapid leaf maturation. Hyphal growth on different carbon sources shows a preference for pectins over starch, cellulose or xylans. In the resistant sylvestris genotypes Ketsch 16 and Ketsch 18 we find that neither spore attachment nor appressorium formation, but hyphal elongation is significantly inhibited as compared to Müller‐Thurgau. Moreover, defence‐related oxidative burst and accumulation of phenolic compounds is stimulated in the resistant genotypes.We arrive at a model, where more rapid maturation of the cell wall in these sylvestris genotypes sequesters pectins as major food source and thus block hyphal elongation. This paves the way for introgression of genetic factors responsible for cell wall maturation into V. vinifera to develop Black Rot‐resistant varieties of grapevine. [ABSTRACT FROM AUTHOR]

Black rot (BR), caused by Guignardia bidwellii, is an emergent fungal disease threatening viticulture and affecting several mildew-tolerant varieties. However, its genetic bases are not fully dissected yet. For this purpose, a segregating population derived from the cross 'Merzling' (hybrid, resistant) × 'Teroldego' (V. vinifera, susceptible) was evaluated for BR resistance at the shoot and bunch level. The progeny was genotyped with the GrapeReSeq Illumina 20K SNPchip, and 7175 SNPs were combined with 194 SSRs to generate a high-density linkage map of 1677 cM. The QTL analysis based on shoot trials confirmed the previously identified Resistance to Guignardia bidwellii (Rgb)1 locus on chromosome 14, which explained up to 29.2% of the phenotypic variance, reducing the genomic interval from 2.4 to 0.7 Mb. Upstream of Rgb1, this study revealed a new QTL explaining up to 79.9% of the variance for bunch resistance, designated Rgb3. The physical region encompassing the two QTLs does not underlie annotated resistance (R)-genes. The Rgb1 locus resulted enriched in genes belonging to phloem dynamics and mitochondrial proton transfer, while Rgb3 presented a cluster of pathogenesis-related Germin-like protein genes, promoters of the programmed cell death. These outcomes suggest a strong involvement of mitochondrial oxidative burst and phloem occlusion in BR resistance mechanisms and provide new molecular tools for grapevine marker-assisted breeding. [ABSTRACT FROM AUTHOR]

This pathogen, which are producing the black rot of grapevine Guignardia bidwelii (Ellis) Viala and Ravaz, and its anamorph Phyllosticta ampelicida (Engelman) van der Aa, is an ascomycete fungus that is responsible for about 5 to 80% production losses in grapevine cultures, although it is less frequent than other fungal diseases from this crop. In the present work, we review the problems related to this pathogen, its life cycle, virulence factors and mode of action, and especially the prevention of the infection and ways to control it, its spread in the world and in our country, We discuss practical considerations for control methods of the black rot, agrotechnical methods, genetical methods, chemical (fungicides, natural products the use of plant resistance stimulators), and biological control. [ABSTRACT FROM AUTHOR]

Resistance to downy mildew (DM) and powdery mildew (PM) contributes to sustainable vineyard management by reducing the diseases and the need for fungicide applications. Resistant varieties vary in their degree of resistance to DM and PM, and in their susceptibility to other diseases. As a consequence, fungicide use may differ among varieties depending on their “resistance patterns” (i.e., the resistance level of a variety toward all of the diseases in the vineyard). The resistance patterns of 16 grapevine varieties to DM, PM, black rot (BR), and gray mold (GM) were evaluated over a 4-year period under field conditions. Disease severity was assessed on leaves and bunches, and the AUDPC (Area Under Disease Progress Curve) was calculated to represent the epidemic progress. GM was found only on bunches and only at very low levels, irrespective of the year or variety, and was therefore excluded from further analyses. The varieties were then grouped into four resistance patterns: i) low resistance to DM and PM, intermediate resistance to BR; ii) high resistance to DM, intermediate resistance to PM, low resistance to BR; iii) intermediate resistance to DM and BR, low resistance to PM; and iv) high resistance to DM, PM, and BR. AUDPC values on leaves were positively correlated with AUDPC values on bunches for susceptible varieties but not for resistant ones, with the exception of PM. Therefore, bioassays with leaves can be used to predict the resistance of bunches to DM and BR for susceptible varieties but not for resistant ones. These results may facilitate both strategic and tactical decisions for the sustainable management of grapevine diseases. [ABSTRACT FROM AUTHOR]

Resistance to downy mildew (DM) and powdery mildew (PM) contributes to sustainable vineyard management by reducing the diseases and the need for fungicide applications. Resistant varieties vary in their degree of resistance to DM and PM, and in their susceptibility to other diseases. As a consequence, fungicide use may differ among varieties depending on their “resistance patterns” (i.e., the resistance level of a variety toward all of the diseases in the vineyard). The resistance patterns of 16 grapevine varieties to DM, PM, black rot (BR), and gray mold (GM) were evaluated over a 4-year period under field conditions. Disease severity was assessed on leaves and bunches, and the AUDPC (Area Under Disease Progress Curve) was calculated to represent the epidemic progress. GM was found only on bunches and only at very low levels, irrespective of the year or variety, and was therefore excluded from further analyses. The varieties were then grouped into four resistance patterns: i) low resistance to DM and PM, intermediate resistance to BR; ii) high resistance to DM, intermediate resistance to PM, low resistance to BR; iii) intermediate resistance to DM and BR, low resistance to PM; and iv) high resistance to DM, PM, and BR. AUDPC values on leaves were positively correlated with AUDPC values on bunches for susceptible varieties but not for resistant ones, with the exception of PM. Therefore, bioassays with leaves can be used to predict the resistance of bunches to DM and BR for susceptible varieties but not for resistant ones. These results may facilitate both strategic and tactical decisions for the sustainable management of grapevine diseases.

Cold-climate wine grapes are produced on 8,000 ha in the North Central region of the United States. Wisconsin has experienced considerable growth, with a 26% increase in acreage since 2017. Chemical management of fungal diseases in cold-climate, interspecific hybrid grapes mirrors that of traditional Vitis vinifera cultivars despite significant differences in disease susceptibility. Most cold-climate cultivars display disease tolerance or resistance to key pathogens such as Plasmopara viticola (downy mildew), Erysiphe necator (powdery mildew), and Phyllosticta ampelicida (black rot). Current fungicide programs in Wisconsin's cold-climate grape industry underutilize genetic resistance, resulting in overreliance on at-risk fungicides and an increased threat of fungicide resistance development. In vineyard trials, the impacts of a reduced fungicide application number compared to current grower "Standard" programs was assessed for disease incidence and severity for five diseases: anthracnose, black rot, downy mildew, Phomopsis cane and leaf spot and powdery mildew. In 2022, with moderate disease pressure at both vineyard sites, there were no significant differences observed when fewer fungicides (six or five applications vs. four applications) were applied. In 2023, higher disease incidence was observed in the "Standard" spray program at one study location which received a greater number of fungicide applications. In both years, grape cultivar was a significant factor with the 'LaCrosse' displaying greater average disease severity than the 'St. Pepin' in both the "Standard" and "Reduced" Programs. These findings present a promising opportunity for cold-climate grape growers to reduce the number of fungicide applications while maintaining disease control and marketable yield.

A study of the impact of pathogenic attack on vine varieties of Cabernet Sauvignon on the content of trans-resveratrol in wine was carried out. Some of the vines were attacked by two pathogens: Botrytis cinerea - a cause of "gray mold"; Phyllosticta ampelicida (asexual phase from Guignardia bidwellii) - the causer of "black rot". It was found that when Botrytis cinerea attacked the vines with high degree (93 %) and index (50.33) (variant V1), this reflected in lower levels of established trans-resveratrol in wine (3.23 mg∙dm-3), in compared to control pathogen-free V2 variant (3.74 mg∙dm-3). The same trend was observed in the attack of the other pathogen. Phyllosticta ampelicida (asexual phase from Guignardia bidwellii), even in low attack degree (10 %) (variant V4) and index (2.5), resulted in lower levels of trans-resveratrol in wine (2.34 mg∙dm-3), compared to control pathogen-free variant V3 (2.56 mg∙dm-3). The study found a lower content of trans-resveratrol in wine produced from grapes of organically grown vines compared to that of conventionally grown.

Guignardia bidwellii (anamorph Phyllosticta ampelicida) is the etiological agent of grape black rot, a disease of economic importance in Europe and a quarantine pest for Mexico. The identification of the anamorphic state by morphological characteristics is complicated, due to the similarity among species of the same genus, for example with the cosmopolitan endophyte G. endophyllicola (P. capitalensis), therefore it is necessary to have quick and specific diagnostic tools. For this purpose, a molecular marker based on single nucleotide polymorphisms (SNP) in the ITS region of the rDNA was developed, where the Bidwell and Ampel2 primers were designed. The PCR amplification generates a fragment of 173 bp, specific to G. bidwellii f. euvitis. The validation of the method showed that there is no cross amplification with closely related phytopathogenic fungi or with the genome of grapevine. The technique was sensitive to detect up to 30 pg μL-1 of DNA from monosporic cultures and in mixture of plant tissue. This diagnostic procedure is presented as a fast and specific option for the monitoring, and detection of G. bidwellii f. euvitis in support of prevention, management, quarantine and eradication strategies of the disease. [ABSTRACT FROM AUTHOR]

Black rot on grapevine is a fungal disease caused by Phyllosticta ampelicida (syn. Guignardia bidwellii) affecting grape leaves as well as clusters. A novel black rot decision support system termed VitiMeteo Black rot was assembled based on existing sub-models and incorporated into the established VitiMeteo forecast and decision support platform. Based on local weather data and a 5-day weather forecast, VitiMeteo Black rot simulates the relative susceptibility of grape clusters, the occurrence and severity of infection events as well as the duration of incubation periods. Data sets obtained in extended international (14 case studies; eight monitoring locations; 11 cultivars; seven countries in Europe and North America) field monitoring campaigns in 2012 and 2013 were used to evaluate the model predictions of newly expressed symptoms on leaves. In the case of the Vitis vinifera cultivars, on average 26.3 disease assessments took place per season. On average, 9.9 predictions were classified as true positive, 8.0 as true negative, 5.2 as false positive and 3.2 as false negative. Model precision, sensitivity and accuracy were on average 64, 77 and 67 %. Potential reasons for false positive and false negative predictions are discussed. VitiMeteo Black rot is freely available for several locations in Germany, Luxembourg and Austria on the internet via the VitiMeteo platform and might be expanded to other regions in the future. [ABSTRACT FROM AUTHOR]

Phyllosticta ampelicida (teleomorph: Guignardia bidwellii) is the fungal plant pathogen that causes black rot on grapevine. It is able to infect all green, expanding grape tissues. Black rot poses a threat to both yield and wine quality; a severe attack can virtually cause a complete crop loss. The fungus is native to North America, and was spread to Europe at the end of the 19th century. With the beginning of the 21st century, an increasing importance of the disease was observed in several European winegrowing regions. Successful black rot control strategies combine sanitary measures, cultural techniques, growing cultivars with reduced susceptibility and the use of effective fungicides. Berries are most susceptible to infections between flowering and bunch closure and consequently, fungicide applications against black rot need to focus on this period. In this paper, forecast models and decision support systems that help to achieve satisfactory control with a minimum of fungicide input are presented. Black rot in grapevine was reported to be well controlled in field experiments by a broad range of fungicide classes including quinone outside inhibitors (98 ± 3% efficacy), demethylation inhibitors (98 ± 3% efficacy) and dithiocarbamates (92 ± 7% efficacy). Average efficacies of other fungicide classes tested so far ranged from 32 to 69%; meta data on the efficacy of fungicides in numerous field trials are given. At present, black rot causes major problems primarily if vineyard management and fungicide use were reduced or abandoned. Organically managed vineyards are highly affected. Hence, site and cultivar selection as well as cultural measures are of the highest importance especially in organic viticulture. Recent studies showed that some strains formerly classified as G. bidwellii in fact belong to a distinct species ( P. parthenocissi). Black rot pathogens produce some phytotoxic secondary metabolites, such as phenguignardic acid, guignardic acid, alaguignardic acid and the guignardianones A, E and F, which could stimulate the development of new herbicides of natural origin. [ABSTRACT FROM AUTHOR]

A drastic pruning strategy was developed to eradicate the fungal disease black rot ( Guignardia bidwellii), which is exotic in Australia, from grapevines, while minimizing the economic cost of returning an affected vineyard to its previous quality and production levels. The protocol involved cutting off vines at the top of the trunk, removing debris from the ground beneath and between vines, mulching the vineyard floor, removing low watershoots during vine regrowth and applying a targeted fungicide programme. The protocol was initially evaluated and consequently modified in Australia using an endemic grapevine disease, black spot or anthracnose ( Elsinoe ampelina), as an analogous model system. Then, it was validated in a black-rot-infested vineyard in New York, USA. Following two seasons of disease-conducive weather conditions, no black rot was detected on treated vines, whereas leaf and fruit infections developed on the untreated control vines. These results confirmed the efficacy of the protocol for eradicating black rot from vineyards while allowing vines to return quickly to previous yield and quality levels without replanting. The protocol may have applicability to disease eradication protocols for other perennial crops as well. Evidence is also presented on the efficacy and potential pitfalls of burning infected grapevine material to eradicate E. ampelina. [ABSTRACT FROM AUTHOR]