Effect of rotation of canola (<i>Brassica napus</i>) cultivars with different complements of blackleg resistance genes on disease severity

Marcroft, S. J.; Wouw, Angela P. Van de; Salisbury, P. A.; Potter, T. D.; Howlett, Barbara J.

doi:10.1111/j.1365-3059.2011.02580.x

Cited by 63 publications

(66 citation statements)

References 41 publications

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“…Unlike Canada, the use of a seed-dressing fungicide in Australia has been shown to gain an economic yield benefit (Marcroft and Potter 2008). Marcroft et al (2012) demonstrated that rotation of R genes can minimise disease pressure by manipulating fungal populations. Since 2012, resistance group(s) based on their R-gene complement has been assigned to all commercial canola varieties in Australia.…”

Section: Integrated Blackleg Management Strategiesmentioning

confidence: 99%

“…This allows GRDC to provide a warning to growers if high level of disease severity is observed in the resistant group. Rotations of cultivars with different components of resistance genes have become evidently effective, but it requires the identification of resistance genes in commercial canola cultivars (Marcroft et al 2012). The combination of major gene resistance and quantitative resistance to L. maculans in canola varieties is able to provide improved durability of blackleg resistance (Brun et al 2010;Marcroft et al 2012;Delourme et al 2014).…”

Section: Integrated Blackleg Management Strategiesmentioning

confidence: 99%

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Insights into fighting against blackleg disease of Brassica napus in Canada

Zhang

Fernando

2018

Crop Pasture Sci.

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Abstract. 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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Section: Integrated Blackleg Management Strategiesmentioning

confidence: 99%

Section: Integrated Blackleg Management Strategiesmentioning

confidence: 99%

Insights into fighting against blackleg disease of Brassica napus in Canada

Zhang

Fernando

2018

Crop Pasture Sci.

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“…In the case of L. maculans , methods for testing the potential efficacy of a set of host resistance combinations by sowing them into the previous years’ stubble have been developed (Marcroft et al., 2012). Our experimental design further allowed us to evaluate changes in the infectivity profile of pathogen populations (including unnecessary infectivity).…”

Section: Discussionmentioning

confidence: 99%

“…This extension of the approach developed by Marcroft et al. (2012) raises the possibility of testing host resistance combinations, not only for efficacy in the following year, but also for stability over several cropping seasons. Clearly, pathogen evolutionary trajectories (i.e., responses to selection pressure) are at least partly determined by the pathotype composition and number of infectivity alleles carried by individuals in the initial pathogen population.…”

Section: Discussionmentioning

confidence: 99%

“…Pictures were taken on a blue background and later scored for infectivity phenotype by a single observer. Two control isolates with known phenotypes D13 ( AvrLm4 , AvrLm6 , VirLepR1 ; Marcroft, Van de Wouw, Salisbury, Potter, & Howlett, 2012) and B12 ( VirLm4 , VirLm6 , AvrLep1; this study) were included in each test, so that both infective (virulent) and noninfective (avirulent) reactions were generated for each variety in each test. From the pictures, tested isolates were scored as infective as soon as one compatible reaction (typical greyish lesion) was observed and noninfective otherwise.…”

Section: Methodsmentioning

confidence: 99%

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Spatio‐temporal connectivity and host resistance influence evolutionary and epidemiological dynamics of the canola pathogen Leptosphaeria maculans

Bousset

Sprague

Thrall

et al. 2018

Evolutionary Applications

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Genetic, physiological and physical homogenization of agricultural landscapes creates ideal environments for plant pathogens to proliferate and rapidly evolve. Thus, a critical challenge in plant pathology and epidemiology is to design durable and effective strategies to protect cropping systems from damage caused by pathogens. Theoretical studies suggest that spatio‐temporal variation in the diversity and distribution of resistant hosts across agricultural landscapes may have strong effects on the epidemiology and evolutionary potential of crop pathogens. However, we lack empirical tests of spatio‐temporal deployment of host resistance to pathogens can be best used to manage disease epidemics and disrupt pathogen evolutionary dynamics in real‐world systems. In a field experiment, we simulated how differences in Brassica napus resistance deployment strategies and landscape connectivity influence epidemic severity and Leptosphaeria maculans pathogen population composition. Host plant resistance, spatio‐temporal connectivity [stubble loads], and genetic connectivity of the inoculum source [composition of canola stubble mixtures] jointly impacted epidemiology (disease severity) and pathogen evolution (population composition). Changes in population composition were consistent with directional selection for the ability to infect the host (infectivity), leading to changes in pathotype (multilocus phenotypes) and infectivity frequencies. We repeatedly observed decreases in the frequency of unnecessary infectivity, suggesting that carrying multiple infectivity genes is costly for the pathogen. From an applied perspective, our results indicate that varying resistance genes in space and time can be used to help control disease, even when resistance has already been overcome. Furthermore, our approach extends our ability to test not only for the efficacy of host varieties in a given year, but also for durability over multiple cropping seasons, given variation in the combination of resistance genes deployed.

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Plant Pathogen Dispersal

West

2014

Encyclopedia of Life Sciences

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Plant disease epidemics require plant pathogens to be dispersed to infect new hosts. Understanding dispersal is important for devising methods to improve detection and control of plant pathogens. This is not straightforward, as plant pathogens can be dispersed by air, rain, water or soil, and by vectors such as animals, pollen, various microbes, people and machinery and on infected plant material including seeds. Epidemics vary in time and space as a result of complex processes affecting inoculum availability and production, dispersal and survival processes, and also the coincidence of susceptible crop plants, which each interact with the weather. To reduce disease, exposure of crops to inoculum is often limited by separating crops in time and space, using crop rotation, including different varieties. A wide range of diagnostic methods are increasingly used to help with this by detecting plant pathogens before infection occurs to prevent introduction of exotic inoculum, or to improve applications of crop protection products. Key Concepts: Plant pathogens include fungi, protists (such as oomycetes and plasmodiophorids), bacteria, phytoplasmas, viruses and viroids. For plant disease epidemics to occur, these plant pathogens must be dispersed to infect new hosts. Plant pathogens can be dispersed by air, rain, water, soil, by animals, people and machinery and through infected plant material including pollen and seeds. A key method for crop protection is to limit dispersal by separating susceptible crops in time and space by crop rotation, use of different varieties, hygiene or management of inoculum and use of crop protection products (biologicals and pesticides) at key growth stages or when infection conditions are suitable. Some pathogens that are dispersed by air are adapted to survive freezing temperatures, high UV light levels and desiccation, whereas others only remain viable for short periods or in certain less extreme conditions. Some may even induce ice nucleation to promote rainfall to return them to the ground. Some plant pathogens are dispersed in rain‐splash, usually short distances but occasionally longer when combined with strong winds. Pathogens can be dispersed in water films and groundwater or rivers. Insects and other invertebrates, pollen and protists may vector some pathogens, mainly viruses, viroids and phytoplasmas. One of the main reasons for new introductions of plant pathogens to a territory is introduction by people, as infected plant material, infected seeds or as contamination on clothing, machinery, food or other imported materials. Various statutory quarantine regulations and inspections by plant health professionals aim to reduce introductions. Climate change may help pathogens to establish in new territories where they were previously absent.

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Effect of rotation of canola (Brassica napus) cultivars with different complements of blackleg resistance genes on disease severity

Cited by 63 publications

References 41 publications

Insights into fighting against blackleg disease of Brassica napus in Canada

Insights into fighting against blackleg disease of Brassica napus in Canada

Spatio‐temporal connectivity and host resistance influence evolutionary and epidemiological dynamics of the canola pathogen Leptosphaeria maculans

Plant Pathogen Dispersal

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