Control of onion downy mildew in the presence of phenylamide-resistant strains of Peronospora destructor (Berk.) Caspary

1992 ◽  
Vol 32 (5) ◽  
pp. 669 ◽  
Author(s):  
RG O'Brien
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Field Trials ◽  
Copper Hydroxide ◽  
Peronospora Destructor ◽  
Phenylamide Fungicides ◽  
Resistant Strains ◽  
Onion Downy Mildew ◽  
Reduce Disease Severity

Two isolates of Peronospora destructor differed in their sensitivities to phenylamide fungicides. An isolate (3014) from the Lockyer Valley did not respond to increasing concentrations of metalaxyl, benalaxyl and oxadixyl between 0.1 and 200 mg a.i./L. An isolate (2967) from Bundaberg was sensitive to these fungicides, with EC50 values (concentrations which reduce disease severity by 50%) of 1.6, 6.0 and 12.1 mg a.i./L, respectively. Isolates 3014 and 2967 were both sensitive to dimethomorph, with EC50 values of 4.3 and 1.4 mg a.i./L, respectively. Field trials compared the efficacy of fungicides for the control of onion downy mildew in the Lockyer Valley in 1989 and 1990. In both trials, treatments containing mancozeb gave the best control, resulting in yield increases of 60% in 1990. There was no difference from the check treatment in either disease severity or yield when metalaxyl was applied, suggesting that phenylamide-resistant strains were prevalent. Other fungicide treatments which did not significantly reduce the severity of downy mildew in the 1990 trial included copper hydroxide, chlorothalonil, fosetyl-Al, and propamocarb. The experimental compound dimethomorph, although less effective than mancozeb, significantly reduced disease severity and increased yield by 24%.

Evaluation of Disease Severity and Molecular Relationships among Peronospora variabilis isolates on Chenopodium species in New Hampshire

Plant Disease ◽  
2021 ◽  
Author(s):  
Haley Breanne Nolen ◽  
Cheryl Smith ◽  
Thomas M Davis ◽  
Anissa M Poleatewich
Keyword(s):  
New England ◽  
Downy Mildew ◽  
Disease Severity ◽  
Sequence Similarity ◽  
Phylogenetic Analyses ◽  
Geographic Location ◽  
Differential Resistance ◽  
Field Trials ◽  
Resistant Variety ◽  
Sources Of Resistance

Quinoa is a potential new crop for New England; however, its susceptibility to downy mildew, caused by Peronospora variabilis, is a key obstacle for cultivation. The objectives of this study were to: 1.) evaluate differential resistance within the Chenopodium genus; 2.) identify novel sources of resistance for use in future genetic studies and/or breeding programs; and 3.) investigate phylogenetic relationships of P. variabilis isolates from different Chenopodium hosts. The long-term goal of this research is to develop a resistant variety of quinoa to be grown in New England. Field trials conducted at UNH evaluated downy mildew disease severity on ten Chenopodium accessions representing four species. Disease severity for each treatment was compared and significant differences in disease severity were observed among accessions. C. berlandierivar. macrocalycium ecotypes collected from Rye Beach, NH and Appledore Island, ME exhibited the lowest disease severity over the growing season. P. variabilis was isolated from each accession and COX2 sequences were compared. Phylogenetic analyses suggest no effect of host species on P. variabilis sequence similarity; however, isolates are shown to cluster by geographic location. This research provides the first step in identifying potential New England native sources of resistance to downy mildew within the genus Chenopodium, and provides preliminary information needed to further investigate resistance at the genomic level in Chenopodium spp.

scholarly journals Use of Bamboo Vinegar as an Alternative to Control Downy Mildew in Maize

2020 ◽  
Vol 3 (2) ◽  
pp. 17-24
Author(s):  
Muhammad Habibullah ◽  
Danes Suhendra
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Disease Incidence ◽  
Leaf Tissue ◽  
Dry Weight ◽  
Positive Control ◽  
Negative Control ◽  
Randomized Design ◽  
Resistant Strains ◽  
Control Application

Introduction: Downy mildew control using pesticides has been used intensively and led to the onset of resistant strains. This research aims to find out the effect of bamboo vinegar administration on disease incidence, disease severity, disease progression, and growth of maize. Materials and Methods: This research was conducted from June to August 2020 in the laboratory and Screenhouse of the Faculty of Agriculture, Universitas Tidar. The experiment was experimentally conducted using a Completely Randomized Design (CRD) consisting of 3 treatments with 6. are plants. In each polybag used there are 3 maize so there are 54 plants tested. The treatment tested is of bamboo vinegar and maydis (negative control), of bamboo vinegar with inoculation P. maydis (positive control), application bamboo vinegar 2 ml l-1 with inoculation P. maydis. Observations on the agronomic influence of maize covering height, , and dry weight were analyzed using ANOVA at a significance of 5% followed by LSD test at the same real level using software R v. 4.0.2. Results: Bamboo vinegar showed lignification in the treatment of stronger bamboo vinegar in corn leaf tissue, did not decrease in disease incidence, but decreased the disease severity by 22.18% and decreased disease the progression by 34.74% based on AUDPC value. The growth of maize, bamboo vinegar-treated shows values are not significant negative control.

scholarly journals Inheritance of resistance against Peronospora destructor in onion cv. ‘Regia’

2020 ◽  
pp. 1999-2009
Author(s):  
Mariana Arias ◽  
Natalia Curbelo ◽  
Pablo González Rabelino ◽  
Esteban Vicente ◽  
Gustavo Giménez ◽  
...  
Keyword(s):  
Disease Severity ◽  
Partial Resistance ◽  
Agronomic Traits ◽  
Selection Process ◽  
Genetic Resistance ◽  
Transgressive Segregation ◽  
Inheritance Of Resistance ◽  
Peronospora Destructor ◽  
Loss Of Susceptibility ◽  
Onion Downy Mildew

Onion downy mildew (DM) caused by Peronospora destructor is a very destructive leaf disease. Genetic resistance is an economic and environmentally friendly way of disease control. In this research, the segregation of DM resistance was analysed in six offspring from crosses between national cultivars and the cv. ‘Regia’, a partial resistance source. F1 plants were self-fertilised, and F1S1 derived progenies were evaluated. The segregations in DM severity were skewed towards susceptibility, with transgressive segregation in five of six progenies. The recessive inheritance could be associated with loss of susceptibility mechanisms. In another experiment, the response of advanced F1S2 lines ‘Regia’ x ‘Pantanoso del Sauce’ were evaluated two times (August and November 2017) in DM disease severity, DM histological quantitative differences, and agronomic traits. F1S2 lines, which have had an earlier selection process, presented an intermediate DM severity between the parents. Disease severity was positively correlated with histological differences in the proportion of infected stomata. ‘Regia’ presented the lowest DM severity and the highest percentage of healthy stomata. Most resistant F1S2 lines did not differ from control cultivars in bulb yield, bulb quality traits and postharvest behaviour, and could be the basis to develop a DM resistant cultivar in comparison to currently grown cultivars

scholarly journals Factors Influencing the Occurrence of Onion Downy Mildew (Peronospora destructor) Epidemics: Trends from 31 Years of Observational Data

Agronomy ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 738 ◽  
Author(s):  
Hervé Van der Heyden ◽  
Pierre Dutilleul ◽  
Jean-Benoît Charron ◽  
Guillaume J. Bilodeau ◽  
Odile Carisse
Keyword(s):  
Downy Mildew ◽  
Observational Data ◽  
Disease Incidence ◽  
Principal Component ◽  
Precipitation Regime ◽  
Peronospora Destructor ◽  
Northern Latitudes ◽  
Regional Basis ◽  
Regional Disease ◽  
Onion Downy Mildew

Onion downy mildew (ODM) caused by Peronospora destructor has been increasing annually in south-western Québec since the early 2000s, reaching 33% of affected onion fields in 2014. Using observational data collected over a period of 31 consecutive years, this study aimed to investigate the variations in ODM incidence and epidemic onset and identify the meteorological variables that influence its polyetic development. A logistic model was fitted to each ODM epidemic to estimate and compare the onset of epidemics on a regional basis. Results of this analysis showed that the first observation date, 10% epidemic onset (b10) and mid-time (b) were, on average, 30.4, 15.1 and 11.3 days earlier in 2007–2017 than in 1987–1996. Results of a principal component analysis suggested that regional disease incidence was mostly influenced by the precipitation regime, the final regional disease incidence the previous year, and warmer temperature during the harvest period the previous fall. Subsequently, the data were divided in three periods of 10, 10 and 11 years, and a discriminant analysis was performed to classify each year in the correct period. Using a sufficient subset of five discriminating variables (temperature and rainfall at harvest the previous fall, winter coldness, solar radiation, and disease incidence the previous year), it was possible to classify 93.5% of the ODM epidemics in the period where they belong. These results suggest that P. destructor may overwinter under northern latitudes and help to highlight the need for more research on overwintering and for the development of molecular-based tools enabling the monitoring of initial and secondary inoculum.

An Epidemic of Downy Mildew caused by Peronospora destructor on Vidalia Sweet Onions in Georgia in 2012

2013 ◽  
Vol 14 (1) ◽  
pp. 54
Author(s):  
Venkatesan Parkunan ◽  
Ronald D. Gitaitis ◽  
Bhabesh Dutta ◽  
David B. Langston ◽  
Pingsheng Ji
Keyword(s):  
Downy Mildew ◽  
Peronospora Destructor ◽  
Recent Outbreak ◽  
The Impact ◽  
Onion Downy Mildew

The first reported occurrence of onion downy mildew (ODM) on Vidalia sweet onions in Georgia was in 1999. Although the disease is not common every year, two epidemics have occurred since 1999. The authors report here on the impact of a recent outbreak of ODM on the $100-million Vidalia onion crop in 2012. Accepted for publication 29 January 2013. Published 28 March 2013.

scholarly journals Epidemiology and management of bacterial leaf spot on watermelon caused byPseudomonas syringae

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1222-1229 ◽  
Author(s):  
E. A. Newberry ◽  
L. Ritchie ◽  
B. Babu ◽  
T. Sanchez ◽  
K. A. Beckham ◽  
...  
Keyword(s):  
Disease Severity ◽  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Negative Relationship ◽  
Disease Outbreaks ◽  
Field Trials ◽  
Multiple Regression Model ◽  
Bacterial Leaf Spot ◽  
Progress Curve ◽  
Cool Conditions

Bacterial leaf spot of watermelon caused by Pseudomonas syringae has been an emerging disease in the southeastern United States in recent years. Disease outbreaks in Florida were widespread from 2013 to 2014 and resulted in foliar blighting at the early stages of the crop and transplant losses. We conducted a series of field trials at two locations over the course of two years to examine the chemical control options that may be effective in management of this disease, and to investigate the environmental conditions conducive for bacterial leaf spot development. Weekly applications of acibenzolar-S-methyl (ASM) foliar, ASM drip, or copper hydroxide mixed with ethylene bis-dithiocarbamate were effective in reducing the standardized area under the disease progress curve (P < 0.05). Pearson’s correlation test demonstrated a negative relationship between the average weekly temperature and disease severity (–0.77, P = 0.0002). When incorporated into a multiple regression model with the square root transformed average weekly rainfall, these two variables accounted for 71% of the variability observed in the weekly disease severity (P < 0.0001). This information should be considered when choosing the planting date for watermelon seedlings as the cool conditions often encountered early in the spring season are conducive for bacterial leaf spot development.

Peronospora destructor. [Descriptions of Fungi and Bacteria].

1975 ◽  
Author(s):  
K. G. Mukerji
Keyword(s):  
South Africa ◽  
New Zealand ◽  
East Asia ◽  
Downy Mildew ◽  
Geographical Distribution ◽  
Wild Species ◽  
Peronospora Destructor ◽  
North East

Abstract A description is provided for Peronospora destructor. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Affects species of Allium; common on A. cepa, rarer on A. ascalonicum, A. fistulosum, A. porrum, A. sativum, A. schoenoprasum, and a few wild species. DISEASE: Downy mildew (mildiou, falscher Mehitau) of onion. GEOGRAPHICAL DISTRIBUTION: On onion in all parts of Europe and America; north, east and south Africa, west, south and east Asia, Australia, New Zealand; and Tasmania. On other Allium crops in a few countries in Europe and on other continents (CMI Map 76. ed. 3, 1969).

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

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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