scholarly journals Assessing the Role of Temperature, Inoculum Density, and Wounding on Disease Progression of the Fungal Pathogen Ceratocystis fimbriata Causing Black Rot in Sweetpotato

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 930-937 ◽  
Author(s):  
M. Stahr ◽  
L. M. Quesada-Ocampo
Keyword(s):  
Disease Management ◽  
Disease Incidence ◽  
Management Strategies ◽  
The United States ◽  
Storage Conditions ◽  
Inoculum Density ◽  
Separate Experiment ◽  
Black Rot ◽  
Disease Development ◽  
Ceratocystis Fimbriata

In 2014, Ceratocystis fimbriata, causal agent of black rot in sweetpotato, reemerged and inflicted large financial losses on growers in the United States. Black rot continues to damage sweetpotatoes and has become a priority to the industry since then. In contrast, little is known about the biology of C. fimbriata and the epidemiology of sweetpotato black rot. In this study, effects of environmental factors such as inoculum density, RH, and temperature on sweetpotato black rot were determined. Cured sweetpotatoes were wounded with a toothpick to simulate puncture wounds, inoculated with different spore suspensions (inoculum density) (104, 105, or 106 spores/ml), and incubated under different RH (85.53, 94.09, or 97.01%) and temperature (13, 18, 23, 29, or 35°C) for 21 days. In a separate experiment, five root wounding types (cuts, punctures, abrasions, end breaks, and macerating bruises) were compared. All wounded roots were subsequently soaked in a 103 spores/ml suspension and incubated at 100% RH and 23°C for 21 days. This study found 29 and 23°C to be the optimal temperature for black rot disease development and sporulation, respectively. No pathogen growth was observed at 13 and 35°C. Increased inoculum density significantly (P < 0.0001) increased disease incidence, but increasing RH had an effect only on sporulation area. All wound types resulted in increased disease incidence and sporulation as early as 7 days postinoculation. Our results highlight the importance of characterizing factors that affect disease development for achieving successful disease management strategies. Findings from this study will be used to improve disease management for sweetpotato black rot by suggesting tighter regulation of curing and storage conditions and better postharvest handling of sweetpotato roots to avoid unnecessary wounding.

scholarly journals Genetic Diversity, Fungicide Sensitivity, and Host Resistance to Ceratocystis fimbriata Infecting Sweetpotato in North Carolina

Plant Disease ◽  
2017 ◽  
Vol 101 (6) ◽  
pp. 994-1001 ◽  
Author(s):  
A. C. Scruggs ◽  
T. Basaiah ◽  
M. L. Adams ◽  
L. M. Quesada-Ocampo
Keyword(s):  
Genetic Diversity ◽  
North Carolina ◽  
Control Strategies ◽  
Management Strategies ◽  
Pcr Amplification ◽  
The United States ◽  
Black Rot ◽  
Ceratocystis Fimbriata ◽  
Fungicide Application

Black rot of sweetpotato, caused by Ceratocystis fimbriata, has recently reemerged as a significant threat to sweetpotato production in North Carolina and other states across the United States. This disease has historically been controlled largely through cultural management strategies and, in some cases, fungicide application. The sudden and destructive reemergence of this disease in 2015 created the need for rapidly evaluating disease control strategies. Genetic diversity of current C. fimbriata isolates infecting sweetpotato in North Carolina was assessed using ITS, TEF, and MAT-2 sequences. All 50 tested isolates were confirmed to be of a single mating type, MAT-2, based on PCR amplification. Alignment of ITS, TEF, and MAT-2 sequences revealed all isolates were identical at each locus. Fourteen common sweetpotato cultivars and advanced breeding lines were screened for black rot resistance using two isolates. None of the cultivars were completely resistant to the disease and most were equally susceptible. ‘Stokes Purple’ and ‘Covington’ were the least susceptible, but significantly (P < 0.05) differed only from ‘Bellevue’, the most susceptible cultivar. Sensitivity of 50 C. fimbriata isolates to difenoconazole, fludioxonil, thiabendazole, dicloran, azoxystrobin, pyraclostrobin, fenamidone, and fluazinam was evaluated in vitro. Difenoconazole, thiabendazole, and fluazinam were most effective in reducing mycelia growth. Postharvest fungicide application on black rot-infected roots provided similar results. Low efficacy of dicloran, as well as a range of EC50 values among isolates, suggests potential resistance to this commonly applied fungicide. Results obtained in this study provide current and useful information so that improved recommendations can be made to reduce losses in sweetpotato to black rot.

Sweetpotato root development influences susceptibility to black rot caused by the fungal pathogen Ceratocystis fimbriata

2021 ◽  
Author(s):  
Camilo Humberto Parada Rojas ◽  
Kenneth Pecota ◽  
Christie Almeyda ◽  
G. Craig Yencho ◽  
Lina Quesada-Ocampo
Keyword(s):  
Root Development ◽  
Disease Incidence ◽  
Black Rot ◽  
Wild Relative ◽  
Storage Root ◽  
Storage Roots ◽  
Ceratocystis Fimbriata ◽  
Breeding Lines ◽  
Below Ground ◽  
Storage Root Development

Black rot of sweetpotato caused by Ceratocystis fimbriata, is an important reemerging disease threatening sweetpotato production in the United States. This study assessed disease susceptibility of the storage root surface, storage root cambium, and slips (vine cuttings) of 48 sweetpotato cultivars, advanced breeding lines, and wild relative accessions. We also characterized the effect of storage root development on susceptibility to C. fimbriata. None of the cultivars examined at the storage root level were resistant, with most cultivars exhibiting similar levels of susceptibility. In storage roots, Jewel and Covington were the least susceptible and significantly different from White Bonita, the most susceptible cultivar. In the slip, significant differences in disease incidence were observed for above and below ground plant structures among cultivars, advanced breeding lines, and wild relative accessions. Burgundy and Ipomoea littoralis displayed less below ground disease incidence as compared to NASPOT 8, Sunnyside and LSU-417, the most susceptible cultivars. Correlation of black rot susceptibility between storage roots and slips was not significant, suggesting that slip assays are not useful to predict resistance in storage roots. Immature, early developing storage roots were comparatively more susceptible than older, fully developed storage roots. The high significant correlation between storage root cross-section area and cross-sectional lesion ratio suggests the presence of an unfavorable environment for C. fimbriata as the storage root develops. Incorporating applications of effective fungicides at transplanting and during early storage root development when sweetpotato tissues are most susceptible to black rot infection may improve disease management efforts.

Effects of Water Temperature, Inoculum Concentration and Age, and Sanitizer Presence on Infection of Ceratocystis fimbriata, Causal Agent of Black Rot in Sweetpotato

Plant Disease ◽  
2020 ◽  
Author(s):  
Madison Stahr ◽  
Lina Quesada-Ocampo
Keyword(s):  
Water Temperature ◽  
Disease Incidence ◽  
Postharvest Disease ◽  
Black Rot ◽  
Storage Roots ◽  
Ceratocystis Fimbriata ◽  
Inoculum Concentration ◽  
Inoculum Age ◽  
Negative Controls ◽  
Water Treatments

Black rot, caused by Ceratocystis fimbriata, is a devastating postharvest disease of sweetpotato that recently re-emerged in 2014. Although the disease is known to develop in storage and during export to overseas markets, little is known as to how pathogen dispersal occurs. This study was designed to investigate dump tank water as a means of dispersal through four different types of water treatments: inoculum concentration (0, 5, 5 × 101, 5 × 102, and 5 × 103 spores/ml), inoculum age (0, 24, 48, 96, and 144 h), water temperature (10, 23, 35, and 45˚C), and presence of a water sanitizer (DryTec, Sanidate, FruitGard, and Selectrocide). Wounded and non-wounded sweetpotato storage roots were soaked in each water treatment for 20-min, stored at 29˚C for a 14-day period, and rated for disease incidence every other day. Disease was observed in sweetpotato storage roots in all water treatments tested, except in the negative controls. Disease incidence decreased with both inoculum concentration and inoculum age, yet values of 16.26% and up to 50% were observed for roots exposed to 5 spores/ml and 144 h water treatments, respectively. Sanitizer products that contained a form of chlorine as the active ingredient significantly reduced disease incidence in storage roots when compared to control roots and roots exposed to a hydrogen-peroxide based product. Finally, no significant differences in final incidence were detected in wounded sweetpotato storage roots exposed to water treatments of any temperature, but a significant reduction in disease progression was observed in the 45˚C treatment. These findings indicate that if packing line dump tanks are improperly managed, they can aid C. fimbriata dispersal through the build-up of inoculum as infected roots are unknowingly washed after storage. Chlorine-based sanitizers can reduce infection when applied after root washing and not in the presence of high organic matter typically found in dump tanks.

scholarly journals Inoculum Density-Disease Development Relationship in Verticillium Wilt of Artichoke Caused by Verticillium dahliae

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1131-1136 ◽  
Author(s):  
M. Berbegal ◽  
A. Ortega ◽  
J. García-Jiménez ◽  
J. Armengol
Keyword(s):  
Population Dynamics ◽  
Verticillium Dahliae ◽  
Symptom Severity ◽  
Disease Incidence ◽  
Growing Season ◽  
Inoculum Density ◽  
Disease Development ◽  
Growing Seasons ◽  
Negative Exponential ◽  
The Relationship

The relationship between inoculum density of Verticillium dahliae in soil and disease development was studied in 10 commercial artichoke fields. Inoculum density of V. dahliae varied between 2.2 and 34.2 microsclerotia (ms) g–1 of soil near planting. Artichoke plants were monitored for disease at the beginning and the end of each growing season. There was a significant correlation, which was best described by negative exponential models, between inoculum density and disease incidence, symptom severity, and recovery of the pathogen from the plants. Inoculum densities ranging from 5 to 9 ms g–1 of soil were associated with a mean percentage of infected plants of about 50%. Additionally, three fields were monitored in two consecutive growing seasons to evaluate the population dynamics of V. dahliae microsclerotia in soil and disease development. Numbers of microsclerotia per gram of soil decreased significantly by the end of the first growing season but slightly increased at the end of the second growing season. In these fields, symptom severity was greatest during the second growing season when high percentages of infected plants also were recorded.

scholarly journals Managing Colletotrichum on Fruit Crops: A “Complex” Challenge

Plant Disease ◽  
2020 ◽  
Vol 104 (9) ◽  
pp. 2301-2316 ◽  
Author(s):  
Madeline Dowling ◽  
Natalia Peres ◽  
Sara Villani ◽  
Guido Schnabel
Keyword(s):  
Disease Management ◽  
Fungicide Resistance ◽  
Tissue Specificity ◽  
Management Strategies ◽  
The United States ◽  
Fruit Crops ◽  
Fungicide Sensitivity ◽  
Species Complexes ◽  
Colletotrichum Spp ◽  
Future Management

The fungal genus Colletotrichum includes numerous important plant pathogenic species and species complexes that infect a wide variety of hosts. Its taxonomy is particularly complex because species’ phenotypes and genotypes are difficult to differentiate. Two notable complexes, C. acutatum and C. gloeosporioides, are known for infecting temperate fruit crops worldwide. Even species within these complexes vary in traits such as tissue specificity, aggressiveness, geographic distribution, and fungicide sensitivity. With few effective chemicals available to control these pathogens, and the persistent threat of fungicide resistance, there is a need for greater understanding of this destructive genus and the methods that can be used for disease management. This review summarizes current research on diseases caused by Colletotrichum spp. on major fruit crops in the United States, focusing on the taxonomy of species involved, disease management strategies, and future management outlook.

scholarly journals Farmer Perceptions on Vegetable Diseases and Their Control in Sub-Humid Areas in Zimbabwe

2019 ◽  
Vol 5 (1) ◽  
pp. 1-11
Author(s):  
Maria Goss ◽  
Paramu. L. Mafongoya ◽  
Augustine Gubba ◽  
Obert Jiri
Keyword(s):  
Disease Management ◽  
Production Systems ◽  
Disease Incidence ◽  
Management Strategies ◽  
Disease Outbreaks ◽  
Weather Conditions ◽  
Cultural Control ◽  
Bacterial Disease ◽  
Vegetable Production ◽  
Control Methods

Abstract The monoculture vegetable production systems practiced by Zimbabwean farmers has resulted in major disease outbreaks, causing major production constraints. There is need to determine the intensity of pesticides usage and methods of alternative disease management strategies. This study was carried out using 250 randomly selected vegetable farmers by administering questionnaires. The study objectives were to determine farmers’ perceptions on vegetable disease incidence and severity in relation to prevailing weather conditions, and determine common control methods practiced to manage fungal and bacterial disease outbreaks. The results indicated significant increases in fungal and bacterial disease incidence of 84.6% (within community cropping fields) and severity of 73.1% (within individual farmer fields) over the past 5-10 years (P £ 0.05). It also revealed disease incidence being highest [30.8%] during winter (May – July) and rainy months [23.1%] (November – February). Results further indicated 96.2% of the respondents relied on chemical methods, 53.8% used cultural control, and 11.5% used natural control methods. However, none of the farmers used bio-pesticide/biological control methods. In conclusion: farmers are aware of the disease shifts in response to different climate variability but seem unaware of the negative effects of extensive chemical use, nor existence of alternative bio-pesticide/biological disease management strategies.

scholarly journals Sweetpotato cultivar susceptibility to infection by Ceratocystis fimbriata

2011 ◽  
Vol 64 ◽  
pp. 1-6 ◽  
Author(s):  
S.L. Lewthwaite ◽  
P.J. Wright ◽  
C.M. Triggs
Keyword(s):  
Crop Production ◽  
Ipomoea Batatas ◽  
Lateral Roots ◽  
The United States ◽  
Black Rot ◽  
Storage Roots ◽  
Ceratocystis Fimbriata ◽  
Susceptibility To Infection ◽  
Cultivar Susceptibility ◽  
Japanese Cultivar

The fungus Ceratocystis fimbriata causes a disease of the sweetpotato (Ipomoea batatas) plant commonly known as black rot This study evaluated sweetpotato cultivar susceptibility to C fimbriata infection During crop production infection of sweetpotato storage roots may take place by transmission from contaminated transplants but generally the pathogen is introduced directly through openings in the periderm These openings may take the form of damaged secondary lateral roots lenticels or wounds In a laboratorybased bioassay storage roots were punctured then pointinoculated with the pathogen Following incubation under warm humid conditions the dimensions of black rot lesions were compared The predominant New Zealand cultivar Owairaka Red was demonstrably less susceptible to C fimbriata than the Japanese cultivar Beniazuma but significantly more susceptible than Beauregard from the United States of America (P

scholarly journals Soilborne Inoculum Density and Environmental Parameters Influence the Development of Pythium Stunt Caused by Pythium tracheiphilum in Head Lettuce Crops

Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1685-1692 ◽  
Author(s):  
Andréanne Sauvageau ◽  
Valérie Gravel ◽  
Hervé Van der Heyden
Keyword(s):  
Disease Risk ◽  
Disease Incidence ◽  
Management Strategies ◽  
Environmental Parameters ◽  
Inoculum Density ◽  
Field Conditions ◽  
Risk Indicators ◽  
Soilborne Disease ◽  
Soil Inoculum ◽  
Dry Soil

In Quebec muck soils, Pythium stunt (Pythium tracheiphilum Matta) is responsible for important yield losses in head lettuce crops each year, which can reach up to 50% in certain cases. Despite the significance of the disease, factors influencing its development remain poorly documented, and no disease risk indicators are available, which makes the development of management strategies difficult. Hence, growers systematically use chemical fungicides throughout the growing season to reduce crop losses. However, it is known that soilborne disease incidence or severity may be influenced by soil inoculum density and environmental parameters. Therefore, the objectives of this study were to investigate the influence of inoculum density on lettuce growth under controlled conditions and evaluate the influence of soil inoculum density, air temperature, relative humidity, and rainfall on disease incidence under field conditions. In particular, this study aims to develop accurate predictors for Pythium stunt incidence. Results showed that, under controlled environment, thresholds of inoculum density of 97 and 46 propagules per gram of dry soil were needed to reduce lettuce dry weight by one-half for cultivars Estival and Prestige, respectively. These results were confirmed under field conditions, where a soil inoculum density >132 propagules per gram of dry soil combined with air temperatures <18°C for the first 2 weeks and rain accumulation >64 mm for the first 3 weeks after transplanting accurately predicted disease incidence 79% of the time. These relationships improve understanding of seasonal Pythium stunt development and will provide useful tools to develop sustainable management strategies.

First Report of Groundnut ringspot virus Infecting Tomato in South Florida

2010 ◽  
Vol 11 (1) ◽  
pp. 49 ◽  
Author(s):  
Craig G. Webster ◽  
Keith L. Perry ◽  
Xiaoyun Lu ◽  
Loren Horsman ◽  
Galen Frantz ◽  
...  
Keyword(s):  
United States ◽  
Disease Management ◽  
Management Strategies ◽  
The United States ◽  
South Florida ◽  
Ringspot Virus ◽  
Integrated Disease Management ◽  
First Report ◽  
Close Relationship ◽  
Relationship Of

To the best of our knowledge this is the first report of GRSV in the United States in any host, although TSWV has been present in Florida for many years. Although the detection of GRSV in Florida tomatoes is cause for concern, the close relationship of GRSV and TSWV may allow successful adaptation of the integrated disease management strategies currently in use for TSWV in tomatoes for management of GRSV. Accepted for publication 17 May 2010. Published 7 July 2010.

scholarly journals Disease Potential of Soil- and Tuberborne Inocula of Colletotrichum coccodes and Black Dot Severity on Potato

Plant Disease ◽  
2008 ◽  
Vol 92 (11) ◽  
pp. 1497-1502 ◽  
Author(s):  
Nadav Nitzan ◽  
Tom F. Cummings ◽  
Dennis A. Johnson
Keyword(s):  
Disease Management ◽  
Management Strategies ◽  
Colletotrichum Coccodes ◽  
Infested Soil ◽  
Disease Development ◽  
Resistance Screening ◽  
Black Dot ◽  
Soil Inoculum ◽  
Foliar Symptoms ◽  
Sclerotial Development

Inoculum of Colletotrichum coccodes, the cause of potato black dot, is soil- or tuberborne. Understanding the disease potential of sources of inocula is crucial for developing disease management strategies and resistance screening techniques. Two hypotheses were tested in this study: (i) soilborne inoculum causes more disease than tuberborne inoculum and (ii) black dot severity is related to the concentration of soilborne inoculum. Trials were conducted in the greenhouse with standardized inoculum. Plants grown in infested soil had more sclerotia on roots than plants grown from infected tubers in three of four trials. In general, plants grown in infested soil produced fewer tubers and lower yields than the noninoculated plants. Plants grown from infected tubers produced similar numbers of tubers as the noninoculated plants in all trials, and had reduced yields in one of the four trials. Increasing concentrations of soilborne inoculum had a nonlinear association with disease development. Foliar symptoms, sclerotial density on roots, and sclerotial development on stems did not increase when soil inoculum exceeded 0.5 or 1.7 g/liters of soil. In this study, soilborne inoculum caused more disease than tuberborne inoculum and disease severity remained constant above a threshold of soilborne inoculum.

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