Elaboration and validation of a diagrammatic scale to assess downy mildew severity in grapevine

The downy mildew, caused by Plasmopora viticola, is one of the most important grapevine (Vitis vinifera) diseases in Southern Brazil, causing defoliation and economic losses. The evaluation of disease severity is an important decision for adoption of strategies and tactics for disease control. Therefore, the objective of this work was to elaborate and to validate a diagrammatic scale to assess downy mildew severity in grapevine, respecting the limitations of visual acuity. The diagrammatic scale with seven levels of disease severity of 1, 3, 6, 12, 25, 50 and 75% was developed in two versions of black-and-white and color scale. The scales were tested and validated by eight raters with and without previous experience with grapevine downy mildew. The raters estimated the severity of 30 grapevine leaves with different downy mildew severity, with and without the use of the scales. Minimum, intermediate and maximum severity levels were collected according to Weber-Fechner's stimulus-response law. The accuracy and precision were analyzed by linear regression between the actual and the estimated severity. Actual severity was assessed with ASSESS(r) Program. The scales provided good levels of accuracy (means of 88%) and excellent levels of precision (means of 95%). The raters showed great precision and accuracy when used the diagrammatic scale. The color scale provided more precise and accurate estimates than the black-and-white scale. The scale proposed in this work presented appropriate applicability for downy mildew evaluation in grapevine.

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Diagrammatic scale to assess downy mildew severity in melon

Horticultura Brasileira ◽

10.1590/s0102-05362009000100015 ◽

2009 ◽

Vol 27 (1) ◽

pp. 76-79 ◽

Cited By ~ 12

Author(s):

Sami J Michereff ◽

Marissônia A Noronha ◽

Gaus SA Lima ◽

Ígor CL Albert ◽

Edilaine A Melo ◽

...

Keyword(s):

Linear Regression ◽

Leaf Area ◽

Downy Mildew ◽

Pseudoperonospora Cubensis ◽

Northeast Brazil ◽

Simple Linear Regression ◽

Standard Methods ◽

Accuracy And Precision ◽

Severity Levels ◽

Diagrammatic Scale

The downy mildew, caused by Pseudoperonospora cubensis, is an important melon disease in Northeast Brazil. Considering the lack of standard methods for its assessment, a diagrammatic scale was developed with 2, 4, 8, 16, 32, 64, 82, and 96% of affected leaf area. The scale was then checked for its accuracy, precision, and reproducibility in estimating downy mildew severity. The diagrammatic scale was validated by eight disease raters; using 50 leaves with different severity levels, previously measured using the software Assess®. Two evaluations were performed on the same set of leaves, but in a different sequence order, by the same raters, within a 15-day interval. The accuracy and precision of each rater was determined by simple linear regression between the actual and the estimated severity. The scale provided good levels of accuracy (means of 87.5%) and excellent levels of precision (means of 94%), with absolute errors concentrated around 10%. Raters showed great repeatability (means of 94%) and reproducibility (>90% in 90.3% of cases) of estimates. Therefore, we could conclude that the diagrammatic scale presented here was suitable for evaluating downy mildew severity in melon.

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RNAi of a Putative Grapevine Susceptibility Gene as a Possible Downy Mildew Control Strategy

Frontiers in Plant Science ◽

10.3389/fpls.2021.667319 ◽

2021 ◽

Vol 12 ◽

Author(s):

Demetrio Marcianò ◽

Valentina Ricciardi ◽

Elena Marone Fassolo ◽

Alessandro Passera ◽

Piero Attilio Bianco ◽

...

Keyword(s):

Gene Expression ◽

Downy Mildew ◽

Disease Severity ◽

Fungal Pathogens ◽

Management Strategies ◽

Susceptibility Gene ◽

Plasmopara Viticola ◽

Pinot Noir ◽

Economic Losses ◽

Reproductive Structures

Downy mildew, caused by the oomycete Plasmopara viticola, is one of the diseases causing the most severe economic losses to grapevine (Vitis vinifera) production. To date, the application of fungicides is the most efficient method to control the pathogen and the implementation of novel and sustainable disease control methods is a major challenge. RNA interference (RNAi) represents a novel biotechnological tool with a great potential for controlling fungal pathogens. Recently, a candidate susceptibility gene (VviLBDIf7) to downy mildew has been identified in V. vinifera. In this work, the efficacy of RNAi triggered by exogenous double-stranded RNA (dsRNA) in controlling P. viticola infections has been assessed in a highly susceptible grapevine cultivar (Pinot noir) by knocking down VviLBDIf7 gene. The effects of dsRNA treatment on this target gene were assessed by evaluating gene expression, disease severity, and development of vegetative and reproductive structures of P. viticola in the leaf tissues. Furthermore, the effects of dsRNA treatment on off-target (EF1α, GAPDH, PEPC, and PEPCK) and jasmonic acid metabolism (COI1) genes have been evaluated. Exogenous application of dsRNA led to significant reductions both in VviLBDIf7 gene expression, 5 days after the treatment, and in the disease severity when artificial inoculation was carried out 7 days after dsRNA treatments. The pathogen showed clear alterations to both vegetative (hyphae and haustoria) and reproductive structures (sporangiophores) that resulted in stunted growth and reduced sporulation. Treatment with dsRNA showed signatures of systemic activity and no deleterious off-target effects. These results demonstrated the potential of RNAi for silencing susceptibility factors in grapevine as a sustainable strategy for pathogen control, underlying the possibility to adopt this promising biotechnological tool in disease management strategies.

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Alternative Products to Control Soybean Downy Mildew in the Field

Journal of Agricultural Science ◽

10.5539/jas.v12n8p160 ◽

2020 ◽

Vol 12 (8) ◽

pp. 160

Author(s):

Gislaine Gabardo ◽

Maristella Dalla Pria ◽

Henrique Luis da Silva ◽

Mônica Gabrielle Harms

Keyword(s):

Downy Mildew ◽

Disease Severity ◽

Field Experiments ◽

Ascophyllum Nodosum ◽

Phenological Stages ◽

Manganese Zinc ◽

Growing Seasons ◽

Progress Curve ◽

Copper Manganese ◽

Diagrammatic Scale

Soybean mildew caused by Oomycota Peronospora manshurica, is a disease widely spread in Brazil. In order to study the efficiency of soybean mildew control due to the application of alternative products and fungicide in the field, experiments were conducted in Ponta Grossa, PR, Brazil, during the 2013/2014 and 2014/2015 growing seasons. The design used was randomized blocks with four replications. The treatments were: 1-witness; 2-acibenzolar-S-methyl; 3-calcium; 4-micronutrients: copper, manganese and zinc; 5-micronutrients: manganese, zinc and molybdenum; 6-NK fertilizer; 7-Ascophyllum nodosum and 8-azoxystrobin + cyproconazole with the addition of Nimbus adjuvant. Four applications of alternative products (phenological stages V3, V6, R1 and R5.1) and two of fungicide (phenological stages R1 and R5.1) were performed. The mildew severity was estimated using a diagrammatic scale. The severity data made it possible to calculate the area under the disease progress curve (AUDPC). In the 2014/2015 harvest the disease was more severe. The control of downy mildew by the use of fungicide did not reduce the epidemic. The fungicide was not efficient in the two evaluated seasons. All tested alternative products reduced the disease severity and AUDPC in both seasons. The best results in reducing downy mildew were found with the application of acibenzolar-S-methyl, micronutrients (Cu, Mn, Zn) and A. nodosum.

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Isolation of Plasmopara viticola from Grapevine Leaves

Proceedings ◽

10.3390/proceedings2019029034 ◽

2019 ◽

Vol 29 (1) ◽

pp. 34

Author(s):

Camelia Ungureanu ◽

Liliana Cristina Soare ◽

Diana Vizitiu ◽

Mirela Calinescu ◽

Irina Fierascu ◽

...

Keyword(s):

Downy Mildew ◽

Plasmopara Viticola ◽

Grapevine Downy Mildew ◽

Grapevine Leaves ◽

Downy Mildew Disease

In order to test some biofungicides, the isolation of Plasmopara viticola was carried out.Plasmopara viticola is a fungus that causes the grapevine downy mildew disease [...]

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Development and validation of a diagrammatic scale for quantifying maize leaf spots caused by Diplodia macrospora

Semina Ciências Agrárias ◽

10.5433/1679-0359.2019v40n6p2475 ◽

2019 ◽

Vol 40 (6) ◽

pp. 2475

Author(s):

Eloisa Lorenzetti ◽

Juliano Tartaro ◽

Alfredo José Alves Neto ◽

Anderson Luis Heling ◽

Jeferson Carlos Carvalho ◽

...

Keyword(s):

Regression Analysis ◽

Disease Severity ◽

Maize Leaf ◽

Stimulus Response ◽

Severity Of Disease ◽

Leaf Spots ◽

Maize Leaves ◽

Severity Levels ◽

Development And Validation ◽

Diagrammatic Scale

The objective of this study was to develop and validate a diagrammatic scale to evaluate the severity of spots on maize leaves caused by the fungus Diplodia macrospora. Severity ranged between the minimal (0.5%) and maximal (55%) limits of disease severity, and intermediate severity levels were defined according to the "Weber-Fechner stimulus response law". The proposed scale describes six levels of severity based on how much of the leaf is affected: 0.5%, 3%, 8%, 23%, 36%, and 55%. Validation was carried out by eight evaluators, four inexperienced and four experienced. They estimated the severity of disease in 60 maize leaves, with and without the proposed diagrammatic scale. A relationship was shown by regression analysis between estimated and actual severity, with and without the use of the scale. When both inexperienced and experienced evaluators used the scale, they were able to estimate disease severity more accurately and precisely.

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High-Throughput Phenotyping of Leaf Discs Infected with Grapevine Downy Mildew Using Shallow Convolutional Neural Networks

Agronomy ◽

10.3390/agronomy11091768 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1768

Author(s):

Daniel Zendler ◽

Nagarjun Malagol ◽

Anna Schwandner ◽

Reinhard Töpfer ◽

Ludger Hausmann ◽

...

Keyword(s):

Downy Mildew ◽

Disease Severity ◽

High Throughput ◽

Imaging System ◽

Leaf Disc ◽

Ground Truth Data ◽

Breeding Lines ◽

Grapevine Downy Mildew ◽

Leaf Discs ◽

Efficient Detection

Objective and standardized recording of disease severity in mapping crosses and breeding lines is a crucial step in characterizing resistance traits utilized in breeding programs and to conduct QTL or GWAS studies. Here we report a system for automated high-throughput scoring of disease severity on inoculated leaf discs. As proof of concept, we used leaf discs inoculated with Plasmopara viticola ((Berk. and Curt.) Berl. and de Toni) causing grapevine downy mildew (DM). This oomycete is one of the major grapevine pathogens and has the potential to reduce grape yield dramatically if environmental conditions are favorable. Breeding of DM resistant grapevine cultivars is an approach for a novel and more sustainable viticulture. This involves the evaluation of several thousand inoculated leaf discs from mapping crosses and breeding lines every year. Therefore, we trained a shallow convolutional neural-network (SCNN) for efficient detection of leaf disc segments showing P. viticola sporangiophores. We could illustrate a high and significant correlation with manually scored disease severity used as ground truth data for evaluation of the SCNN performance. Combined with an automated imaging system, this leaf disc-scoring pipeline has the potential to considerably reduce the amount of time during leaf disc phenotyping. The pipeline with all necessary documentation for adaptation to other pathogens is freely available.

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Solar radiation affects grapevine susceptibility to Plasmopara Viticola

Scientia Agricola ◽

10.1590/s0103-90162008000700011 ◽

2008 ◽

Vol 65 (spe) ◽

pp. 65-70 ◽

Cited By ~ 4

Author(s):

Anna Dalla Marta ◽

Valentina Di Stefano ◽

Zoran G. Cerovic ◽

Giovanni Agati ◽

Simone Orlandini

Keyword(s):

Solar Radiation ◽

Downy Mildew ◽

Disease Severity ◽

Inverse Relationship ◽

Direct Action ◽

Growing Season ◽

Plasmopara Viticola ◽

Polyphenolic Content ◽

Grapevine Leaves ◽

Plant Compounds

Solar radiation plays an important role in the development of some fungal diseases due to its direct action on the microorganisms and also its indirect effect on the production of specific plant compounds. This experiment examined the effect of two light environments (100% and 35% of full strength) on the polyphenolic content of grapevine leaves and quantified their relation to resistance to downy mildew (Plasmopara viticola). Leaf epidermal polyphenolic contents were non-destructively measured during the growing season 2006 using the Dualex chlorophyll fluorescence-based portable leaf-clip. The experimental design consisted of six parcels of 30 vines and measurements were performed on the 12 central vines. The leaves were inoculated with a sporangia suspension containing 50,000 sporangia of P. viticola per mL and the disease severity was assessed after the appearance of symptoms. Leaves maintained at 100% sun had high polyphenolic content and significantly lower disease severity compared to leaves under shading nets. These results indicate an inverse relationship between produced polyphenolics and downy mildew severity.

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Kaolin Particle Film Protects Grapevine cv. Cabernet Sauvignon Against Downy Mildew by Forming Particle Film at the Leaf Surface, Directly Acting on Sporangia and Inducing the Defense of the Plant

Frontiers in Plant Science ◽

10.3389/fpls.2021.796545 ◽

2022 ◽

Vol 12 ◽

Author(s):

Ying Wang ◽

Xiao Cao ◽

Yulei Han ◽

Xing Han ◽

Zhilei Wang ◽

...

Keyword(s):

Plant Defense ◽

Downy Mildew ◽

Leaf Surface ◽

Plasmopara Viticola ◽

Defense Responses ◽

Management Program ◽

Oxidative Enzymes ◽

Grapevine Downy Mildew ◽

Protected Plants ◽

Grapevine Leaves

Downy mildew is a major threat to viticulture, leading to severe yield loss. The use of traditional copper-based fungicides is effective, but has adverse effects on the environment and human health, making it urgent to develop an environmentally friendly disease management program. Multi-functional kaolin particle film (KPF) is promising as an effective and safer treatment strategy, since this material lacks chemically active ingredients. In this study, ability of Kaolin particle film (KPF) pretreatment to protect grapevine leaves from Plasmopara viticola was tested and the mode of action of KPF was analyzed. KPF application reduced the disease severity and the development of intercellular hyphae. Additionally, there was reduced accumulation of H2O2 and malondialdehyde (MDA) with pretreatment. The observation of ultrastructure on the leaf surface showed KPF deposition and stomatal obstruction, indicating that KPF protected plants against disease by preventing the adhesion of pathogens to the leaf surface and blocking invasion through the stomata. KPF pretreatment also activated host defense responses, as evidenced by increased activities of anti-oxidative enzymes [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)] and defense-related enzymes [phenylalanine ammonia-lyase (PAL), chitinases, and β-1,3-glucanases], increased phytohormone signals [abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA)] and the up-regulation of defense genes related to plant defense. Overall, these results demonstrate that KPF treatment counters grapevine downy mildew by protecting leaves and enhancing plant defense responses.

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Diagrammatic scale for assessment of soybean rust severity

Fitopatologia Brasileira ◽

10.1590/s0100-41582006000100011 ◽

2006 ◽

Vol 31 (1) ◽

pp. 63-68 ◽

Cited By ~ 110

Author(s):

Cláudia V. Godoy ◽

Lucimara J. Koga ◽

Marcelo G. Canteri

Keyword(s):

Glycine Max ◽

Scale Validation ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Stimulus Response ◽

Accuracy And Precision ◽

Rust Severity ◽

Severity Levels ◽

Diagrammatic Scale

A diagrammatic scale to assess soybean (Glycine max) rust severity, caused by the fungus Phakopsora pachyrhizi, was developed in this study. Leaflets showing different severity levels were collected for determination of the minimum and maximum severity limits; intermediate levels were determined according to "Weber-Fechner's stimulus-response law". The proposed scale showed the levels of 0.6; 2; 7; 18; 42, and 78.5%. Scale validation was performed by eight raters (four inexperienced and four experienced), who estimated the severity of 44 soybean leaflets showing rust symptoms, with and without the use of the scale. Except for rater number eight, all showed a tendency to overestimate severity without the aid of the diagrammatic scale. With the scale, the raters obtained better accuracy and precision levels, although the tendency to overestimate was maintained. Experienced raters were more accurate and precise than inexperienced raters, and assessment improvements with the use of the scale were more significant for inexperienced raters.

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High-throughput phenotyping of leaf discs infected with grapevine downy mildew using shallow convolutional neural networks

10.1101/2021.08.19.456931 ◽

2021 ◽

Author(s):

Daniel Zendler ◽

Nagarjun Malagol ◽

Anna Schwandner ◽

Reinhard Töpfer ◽

Ludger Hausmann ◽

...

Keyword(s):

Downy Mildew ◽

Disease Severity ◽

High Throughput ◽

Imaging System ◽

Leaf Disc ◽

Ground Truth Data ◽

Breeding Lines ◽

Grapevine Downy Mildew ◽

Leaf Discs ◽

Efficient Detection

Objective and standardized recording of disease severity in mapping crosses and breeding lines is a crucial step in characterizing resistance traits utilized in breeding programs and to conduct QTL or GWAS studies. Here we report a system for automated high-throughput scoring of disease severity on inoculated leaf discs. As proof of concept, we used leaf discs inoculated with Plasmopara viticola causing grapevine downy mildew (DM). This oomycete is one of the major grapevine pathogens and has the potential to reduce grape yield dramatically if environmental conditions are favorable. Breeding of DM resistant grapevine cultivars is an approach for a novel and more sustainable viticulture. This involves the evaluation of several thousand inoculated leaf discs from mapping crosses and breeding lines every year. Therefore, we trained a shallow convolutional neural-network (SCNN) for efficient detection of leaf disc segments showing P. viticola sporangiophores. We could illustrate a high and significant correlation with manually scored disease severity used as ground truth data for evaluation of the SCNN performance. Combined with an automated imaging system, this leaf disc-scoring pipeline has the potential to reduce the amount of time during leaf disc phenotyping considerably. The pipeline with all necessary documentation for adaptation to other pathogens is freely available.

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