Blackleg disease of canola in Australia

Blackleg disease caused by the fungus Leptosphaeria maculans is the most important disease of canola worldwide. The impact of this disease on the development of the Australian canola industry, particularly over the last 20 years, is discussed. Deployment of a range of disease control measures has resulted in a thriving canola industry with production now approaching 4 million tonnes annually. Discoveries about disease mechanisms and key plant and fungal genes are described. Analysis of the L. maculans genome sequence has enabled an understanding of how fungal populations can evolve rapidly to overcome disease resistance bred into canola cultivars.

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Insights into fighting against blackleg disease of Brassica napus in Canada

Crop and Pasture Science ◽

10.1071/cp16401 ◽

2018 ◽

Vol 69 (1) ◽

pp. 40 ◽

Cited By ~ 18

Author(s):

Xuehua Zhang ◽

W. G. Dilantha Fernando

Keyword(s):

Brassica Napus ◽

Disease Control ◽

Resistance Genes ◽

Leptosphaeria Maculans ◽

Western Canada ◽

R Genes ◽

Blackleg Disease ◽

Evolutionary Potential ◽

Fungal Populations ◽

Major Resistance Genes

Blackleg disease, caused by the ascomycete fungal pathogen Leptosphaeria maculans, is a devastating disease of canola (Brassica napus) in Australia, Canada and Europe. Although cultural strategies such as crop rotation, fungicide application, and tillage are adopted to control the disease, the most promising disease control strategy is the utilisation of resistant canola varieties. However, field populations of L. maculans display a high evolutionary potential and are able to overcome major resistance genes within a few years, making disease control relying on resistant varieties challenging. In the early 1990s, blackleg resistance gene Rlm3 was introduced into Canadian canola varieties and provided good resistance against the fungal populations until the early 2000s, when moderate to severe blackleg outbreaks were observed in some areas across western Canada. However, the breakdown of Rlm3 resistance was not reported until recently, based on studies on R genes present in Canadian canola varieties and the avirulence allele frequency in L. maculans populations in western Canada. The fact that Rlm3 was overcome by the evolution of fungal populations demands canola breeding programs in Canada to be prepared to develop canola varieties with diversified and efficient R genes. In addition, frequent monitoring of fungal populations can provide up-to-date guidance for proper resistance genes deployment. This literature review provides insights into the outbreaks and management of blackleg disease in Canada.

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The impact of contact structure on infectious disease control: influenza and antiviral agents

Epidemiology and Infection ◽

10.1017/s0950268807007959 ◽

2007 ◽

Vol 135 (7) ◽

pp. 1124-1132 ◽

Cited By ~ 18

Author(s):

H.-P. DUERR ◽

M. SCHWEHM ◽

C. C. LEARY ◽

S. J. De Vlas ◽

M. EICHNER

Keyword(s):

Disease Control ◽

Contact Structure ◽

Influenza Pandemic ◽

Antiviral Treatment ◽

Antiviral Agents ◽

Emerging Infectious Diseases ◽

Control Measures ◽

Variable Degree ◽

Contact Patterns ◽

The Impact

SUMMARYPlanning adequate public health responses against emerging infectious diseases requires predictive tools to evaluate the impact of candidate intervention strategies. With current interest in pandemic influenza very high, modelling approaches have suggested antiviral treatment combined with targeted prophylaxis as an effective first-line intervention against an emerging influenza pandemic. To investigate how the effectiveness of such interventions depends on contact structure, we simulate the effects in networks with variable degree distributions. The infection attack rate can increase if the number of contacts per person is heterogeneous, implying the existence of high-degree individuals who are potential super-spreaders. The effectiveness of a socially targeted intervention suffers from heterogeneous contact patterns and depends on whether infection is predominantly transmitted to close or casual contacts. Our findings imply that the various contact networks' degree distributions as well as the allocation of contagiousness between close and casual contacts should be examined to identify appropriate strategies of disease control measures.

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The African swine fever control zone in South Africa and its current relevance

Onderstepoort Journal of Veterinary Research ◽

10.4102/ojvr.v83i1.1034 ◽

2016 ◽

Vol 83 (1) ◽

Cited By ~ 6

Author(s):

Noluvuyo R. Magadla ◽

Wilna Vosloo ◽

Livio Heath ◽

Bruce Gummow

Keyword(s):

South Africa ◽

Disease Control ◽

African Swine Fever ◽

Control Measures ◽

Maximum Temperature ◽

Boundary Line ◽

Control Line ◽

Control Zone ◽

Ornithodoros Moubata ◽

The Impact

African swine fever (ASF) has been reported in South Africa since the early 20th century. The disease has been controlled and confined to northern South Africa over the past 80 years by means of a well-defined boundary line, with strict control measures and movement restrictions north of this line. In 2012, the first outbreak of ASF outside the ASF control zone since 1996 occurred. The objective of this study was to evaluate the current relevance of the ASF control line as a demarcation line between endemic ASF (north) areas and ASF-free (south) area and to determine whether there was a need to realign its trajectory, given the recent outbreaks of ASF, global climate changes and urban development since the line’s inception. A study of ASF determinants was conducted in an area 20 km north and 20 km south of the ASF control line, in Limpopo, Mpumalanga, North West and Gauteng provinces between May 2008 and September 2012. The study confirmed that warthogs, warthog burrows and the soft tick reservoir, Ornithodoros moubata, are present south of the ASF control line, but no virus or viral DNA was detected in these ticks. There appears to be an increasing trend in the diurnal maximum temperature and a decrease in humidity along the line, but the impact of these changes is uncertain. No discernible changes in minimum temperatures and average rainfall along the disease control line were observed between 1992 and 2014. Even though the reservoirs were found south of the ASF boundary line, the study concluded that there was no need to realign the trajectory of the ASF disease control line, with the exception of Limpopo Province. However, the provincial surveillance programmes for the reservoir, vector and ASF virus south of this line needs to be maintained and intensified as changing farming practices may favour the spread of ASF virus beyond the control line.Keywords: African swine fever; warthog burrow; Ornithodoros moubata;control line

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Individually Optimal Choices can be Collectively Disastrous in COVID-19 Disease Control

10.21203/rs.3.rs-143573/v1 ◽

2021 ◽

Author(s):

Madison Stoddard ◽

Debra Van Egeren ◽

Kaitlyn Johnson ◽

Smriti Rao ◽

Josh Furgeson ◽

...

Keyword(s):

Public Health ◽

Disease Control ◽

Control Measures ◽

Disease Spread ◽

Complete Suppression ◽

Natural Immunity ◽

Endemic Disease ◽

Health Measures ◽

The Impact

Abstract Background: The word ‘pandemic’ conjures dystopian images of bodies stacked in the streets and societies on the brink of collapse. Despite this frightening picture, denialism and noncompliance with public health measures are common in the historical record, for example during the 1918 Influenza pandemic or the 2015 Ebola epidemic. The unique characteristics of SARS-CoV-2—its high basic reproduction number (R0), time-limited natural immunity and considerable potential for asymptomatic spread—exacerbate the public health repercussions of noncompliance with interventions (such as vaccines and masks) to limit disease transmission. Our work explores the rationality and impact of noncompliance with COVID-19 disease control measures. Methods: In this work, we used game theory to explore when noncompliance confers a perceived benefit to individuals. We then used epidemiological modeling to predict the impact of noncompliance on control of COVID-19, demonstrating that the presence of a noncompliant subpopulation prevents suppression of disease spread. Results: Our modeling demonstrating that noncompliance is a Nash equilibrium under a broad set of conditions, and that the existence of a noncompliant population can result in extensive endemic disease in the long-term after a return to pre-pandemic social and economic activity. Endemic disease poses a threat for both compliant and noncompliant individuals; all community members are protected if complete suppression is achieved, which is only possible with a high degree of compliance. For interventions that are highly effective at preventing disease spread, however, the consequences of noncompliance are borne disproportionately by noncompliant individuals. Conclusions: In sum, our work demonstrates the limits of free-market approaches to compliance with disease control measures during a pandemic. The act of noncompliance with disease intervention measures creates a negative externality, rendering COVID-19 disease control ineffective in the short term and making complete suppression impossible in the long term. Our work underscores the importance of developing effective strategies for prophylaxis through public health measures aimed at complete suppression and the need to focus on compliance at a population level.

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MODELING CHOLERA TRANSMISSION UNDER DISEASE CONTROL MEASURES

Journal of Biological System ◽

10.1142/s0218339021400015 ◽

2020 ◽

pp. 1-26

Author(s):

MARGARET BROWN ◽

MIKO JIANG ◽

CHAYU YANG ◽

JIN WANG

Keyword(s):

Disease Control ◽

Disease Transmission ◽

Control Measures ◽

Transmission Dynamics ◽

Threshold Dynamics ◽

Education Programs ◽

Multiple Control ◽

Indirect Transmission ◽

Transmission Pathways ◽

The Impact

We present a new mathematical model to investigate the transmission dynamics of cholera under disease control measures that include education programs and water sanitation. The model incorporates the impact of education programs into the disease transmission rates and that of water sanitation into the environmental pathogen dynamics. We conduct a detailed analysis to the autonomous system of the model and establish the local and global stabilities of its equilibria that characterize the threshold dynamics of cholera. We then perform an optimal control study on the general model with time-dependent controls and explore effective approaches to implement the education programs and water sanitation while balancing their costs. Our analysis and simulation highlight the complex interaction among the direct and indirect transmission pathways of the disease, the intrinsic growth of the environmental pathogen and the impact of multiple control measures, and their roles in collectively shaping the transmission dynamics of cholera.

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Usefulness of winter canola (Brassica napus) race-specific resistance genes against blackleg (causal agent Leptosphaeria maculans) in southern Australian growing conditions

Crop and Pasture Science ◽

10.1071/cp10187 ◽

2011 ◽

Vol 62 (2) ◽

pp. 162 ◽

Cited By ~ 16

Author(s):

K. A. Light ◽

N. N. Gororo ◽

P. A. Salisbury

Keyword(s):

Disease Resistance ◽

Resistance Genes ◽

Leptosphaeria Maculans ◽

Brassica Species ◽

Superior Performance ◽

Adult Plant ◽

Control Line ◽

Blackleg Disease ◽

Blackleg Resistance ◽

Spring Canola

Studies on the blackleg resistance of Brassica lines containing known race-specific, Rlm resistance genes can provide information on the potential use of these genes in the genetic improvement of Australian spring canola lines. Lines of four Brassica species (winter B. napus, B. nigra, B. juncea, B. rapa) containing one or more known specific Rlm genes were assessed for seedling and adult plant survival, on infected stubble derived from crops of both polygenic and B. rapa ssp. sylvestris resistance types, to determine their potential usefulness as sources of blackleg disease resistance in diverse environments in southern Australia. Seedling and adult plant resistance of lines differed depending on the stubble type used. The seedling and adult plant blackleg resistance of several lines containing the resistance genes Rlm1, Rlm1/Rlm3, Rlm7, and Rlm10 was consistently higher than the control line, AV-Sapphire, which carries polygenic resistance. The superior performance of these lines indicates that winter B. napus and B. nigra lines have outstanding potential for improving blackleg disease resistance under Australian conditions.

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Control of Simultaneous Outbreaks of Carbapenemase-Producing Enterobacteriaceae and Extensively Drug-ResistantAcinetobacter baumanniiInfection in an Intensive Care Unit Using Interventions Promoted in the Centers for Disease Control and Prevention 2012 Carbapenemase-Resistant Enterobacteriaceae Toolkit

Infection Control and Hospital Epidemiology ◽

10.1086/676857 ◽

2014 ◽

Vol 35 (7) ◽

pp. 810-817 ◽

Cited By ~ 33

Author(s):

Kyle B. Enfield ◽

Nujhat N. Huq ◽

Megan F. Gosseling ◽

Darla J. Low ◽

Kevin C. Hazen ◽

...

Keyword(s):

Intensive Care Unit ◽

Intensive Care ◽

Infection Control ◽

Disease Control ◽

Control Measures ◽

Surgical Trauma ◽

Infection Control Measures ◽

Resistance Plasmids ◽

Centers For Disease Control ◽

The Impact

ObjectiveWe describe the efficacy of enhanced infection control measures, including those recommended in the Centers for Disease Control and Prevention’s 2012 carbapenem-resistant Enterobacteriaceae (CRE) toolkit, to control concurrent outbreaks of carbapenemase-producing Enterobacteriaceae (CPE) and extensively drug-resistantAcinetobacter baumannii(XDR-AB).DesignBefore-after intervention study.SettingFifteen-bed surgical trauma intensive care unit (ICU).MethodsWe investigated the impact of enhanced infection control measures in response to clusters of CPE and XDR-AB infections in an ICU from April 2009 to March 2010. Polymerase chain reaction was used to detect the presence ofblaKPCand resistance plasmids in CRE. Pulsed-field gel electrophoresis was performed to assess XDR-AB clonality. Enhanced infection-control measures were implemented in response to ongoing transmission of CPE and a new outbreak of XDR-AB. Efficacy was evaluated by comparing the incidence rate (IR) of CPE and XDR-AB before and after the implementation of these measures.ResultsThe IR of CPE for the 12 months before the implementation of enhanced measures was 7.77 cases per 1,000 patient-days, whereas the IR of XDR-AB for the 3 months before implementation was 6.79 cases per 1,000 patient-days. All examined CPE shared endemicblaKPCresistance plasmids, and 6 of the 7 XDR-AB isolates were clonal. Following institution of enhanced infection control measures, the CPE IR decreased to 1.22 cases per 1,000 patient-days (P= .001), and no more cases of XDR-AB were identified.ConclusionsUse of infection control measures described in the Centers for Disease Control and Prevention’s 2012 CRE toolkit was associated with a reduction in the IR of CPE and an interruption in XDR-AB transmission.

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Identifying resistance genes to Leptosphaeria maculans in Australian Brassica napus cultivars based on reactions to isolates with known avirulence genotypes

Crop and Pasture Science ◽

10.1071/cp11341 ◽

2012 ◽

Vol 63 (4) ◽

pp. 338 ◽

Cited By ~ 44

Author(s):

Steve J. Marcroft ◽

Vicki L. Elliott ◽

Anton J. Cozijnsen ◽

Phillip A. Salisbury ◽

Barbara J. Howlett ◽

...

Keyword(s):

Brassica Napus ◽

Resistance Genes ◽

Adult Plant Resistance ◽

Leptosphaeria Maculans ◽

Mortality Data ◽

Adult Plant ◽

Blackleg Disease ◽

Seedling Resistance ◽

Breeding Lines ◽

Fungal Populations

Blackleg disease, caused by the fungus Leptosphaeria maculans, is the major disease of canola (Brassica napus) worldwide. A set of 12 Australian L. maculans isolates was developed and used to characterise seedling resistance in 127 Australian cultivars and advanced breeding lines. Plant mortality data used to assess the effectiveness of seedling resistance in canola growing regions of Australia showed that Rlm3 and Rlm4 resistance genes were less effective than other seedling resistance genes. This finding was consistent with regional surveys of the pathogen, which showed the frequency of Rlm4-attacking isolates was >70% in fungal populations over a 10-year period. Differences in adult plant resistance were identified in a subset of Australian cultivars, indicating that some adult gene resistance is isolate-specific.

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Yield losses in canola in response to blackleg disease

Canadian Journal of Plant Science ◽

10.1139/cjps-2019-0259 ◽

2020 ◽

Vol 100 (5) ◽

pp. 488-494

Author(s):

Yixiao Wang ◽

Stephen E. Strelkov ◽

Sheau-Fang Hwang

Keyword(s):

Disease Severity ◽

Field Experiments ◽

Leptosphaeria Maculans ◽

Economic Benefits ◽

Control Measures ◽

Yield Losses ◽

Blackleg Disease ◽

Brassica Napus L ◽

Moderately Resistant ◽

The Relationship

Blackleg, caused by Leptosphaeria maculans (Desm.) Ces. & De Not., is an important disease of canola (Brassica napus L.) worldwide. In Canada, blackleg is managed mainly by the cultivation of resistant or moderately resistant canola hybrids. Field experiments were conducted in Edmonton, AB, Canada, in 2017 and 2018 to determine the relationship between blackleg disease severity and yield in the moderately resistant canola hybrids ‘73-15RR’ and ‘1950RR’. Blackleg severity was rated on a 0–5 scale, where 0 = no disease and 5 = plant death. Regression analysis showed that relationships between disease severity and pod number and seed yield were best explained by second-degree quadratic equations in all site-years for both cultivars. Percentage yield loss increased by 18%–99% and 26%–86% in plants of ‘73-15RR’ and ‘1950RR’, respectively, with disease severities of 2–5 compared with plants with severities of 0–1. An improved knowledge of the relationship between blackleg severity and yield losses is important for a more accurate evaluation of the agronomic efficacy and economic benefits of control measures.

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