<i>Ramularia collo-cygni</i>—An Emerging Pathogen of Barley Crops

Havis, Neil D.; Brown, J. K. M.; Clemente, G.E.; Frei, P.; Jędryczka, M.; Kaczmarek, Joanna; Kaczmarek, Maciej; Matušinsky, Pavel; McGrann, Graham R. D.; Pereyra, Silvia; Piotrowska, Monika Joanna; Sghyer, Hind; Tellier, Aurélien; Heß, Michael

doi:10.1094/phyto-11-14-0337-fi

Cited by 78 publications

(96 citation statements)

References 35 publications

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“…However, it is only since the mid-1980's that there is a significant increase of R. collo-cygni DNA in the grain. Indeed, coinciding with more frequent observations of RLS symptoms from the field [1].…”

Section: Discussionsupporting

confidence: 78%

“…The timetree shown was generated using the RelTime method [36]. Divergence times for all branching points in the topology were calculated using the Maximum Likelihood method based on the JTT matrix-based model [1]. The estimated log likelihood value of the topology shown is -61359.70.…”

Section: Species Phylogeny and Divergence Time Calculationsmentioning

confidence: 99%

“…They need to be controlled to achieve sufficient yield and best quality of the agricultural products. The ascomycete fungus Ramularia collo-cygni has been detected in barley samples worldwide [1]. The filamentous fungus is the major biotic agent of a leaf spotting complex [2] typically occurring late in the growing season on the upper canopy [3].…”

Section: Introductionmentioning

confidence: 99%

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The evolutionary history of the current globalRamularia collo-cygniepidemic

Stam¹,

Sghyer²,

Münsterkötter

et al. 2017

Preprint

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Ramularia Leaf Spot (RLS) has emerged as a threat for barley production in many regions of the world. Late appearance of unspecific symptoms caused that Ramularia collo-cygni could only by molecular diagnostics be detected as the causal agent of RLS. Although recent research has shed more light on the biology and genomics of the pathogen, the cause of the recent global spread remains unclear.To address urgent questions, especially on the emergence to a major disease, life-cycle, transmission, and quick adaptation to control measures, we de-novo sequenced the genome of R. collo-cygni (urug2 isolate). Additionally, we sequenced fungal RNA from 6 different conditions, which allowed for an improved genome annotation. This resulted in a high quality draft assembly of about 32 Mb, with only 78 scaffolds with an N50 of 2.1 Mb. The overall annotation enabled the prediction of 12.346 high confidence genes. Genomic comparison revealed that R. collo-cygni has significantly diverged from related Dothidiomycetes, including gain and loss of putative effectors, however without obtaining species-specific genome features. To evaluate the species-wide genetic diversity, we sequenced the genomes of 19 R. collo-cygni isolates from multiple geographic locations and diverse hosts and mapped sequences to our reference genome. Admixture analyses show that R. collo-cygni is world-wide genetically uniform and that samples do not show a strong clustering on either geographical location or host species. To date, the teleomorph of R. collo-cygni has not been observed. Analysis of linkage disequilibrium shows that in the world-wide sample set there are clear signals of recombination and thus sexual reproduction, however these signals largely disappear when excluding three outliers samples, suggesting that the main global expansion of R. collo-cygni comes from mixed or clonally propagating populations. We further analysed the historic population size (Ne) of R. collo-cygni using Bayesian simulations.We discuss how our genomic data and population genetics analysis can help understand the current R. collocygni epidemic and provide different hypothesis that are supported by our data. We specifically highlight how recombination, clonal spreading and lack of host-specificity could further support global epidemics of this increasingly recognized plant disease and suggest specific approaches to combat this pathogen.

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Section: Discussionsupporting

confidence: 78%

Section: Species Phylogeny and Divergence Time Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The evolutionary history of the current globalRamularia collo-cygniepidemic

Stam¹,

Sghyer²,

Münsterkötter

et al. 2017

Preprint

Self Cite

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“…The fungal pathogen species we encountered are congeners of important cereal pathogens, including Pyrenophora , Parastagonospora , and Ramularia spp., which cause major yield losses and often specialize on host genotypes (Havis et al. , McDonald and Stukenbrock ). Our results imply that naturally occurring host genetic and species diversity may mitigate the spread of highly virulent pathogens in wild grassland systems (McDonald and Stukenbrock ).…”

Section: Discussionmentioning

confidence: 99%

Foliar pathogens are unlikely to stabilize coexistence of competing species in a California grassland

Spear

Mordecai

2018

Ecology

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Pathogen infection is common in wild plants and animals, and may regulate their populations. If pathogens have narrow host ranges and increase with the density of their favored hosts, they may promote host species diversity by suppressing common species to the benefit of rare species. Yet, because many pathogens infect multiple co-occurring hosts, they may not strongly respond to the relative abundance of a single host species. Are natural communities dominated by specialized pathogens that respond to the relative abundance of a specific host or by pathogens with broad host ranges and limited responses to the relative abundance of single host? The answer determines the potential for pathogens to promote host coexistence, as often hypothesized, or to have negligible or even negative effects on host coexistence. We lack a systematic understanding of the impacts, identities, and host ranges of pathogens in natural communities. Here we characterize a community of foliar fungal pathogens and evaluate their host specificity and fitness impacts in a California grassland community of native and exotic species. We found that most of the commonly isolated fungal pathogens were multi-host, with intermediate to low specialization. The amount of pathogen damage each host experienced was independent of host species local relative abundance. Despite pathogen sharing among the host species, fungal communities slightly differed in composition across host species. Plants with high pathogen damage tended to have lower seed production but the relationship was weak, suggesting limited fitness impacts. Moreover, seed production was not dependent on the local relative abundance of each plant species, suggesting that stabilizing coexistence mechanisms may operate at larger spatial scales in this community. Because foliar pathogens in this grassland community are multi-host and have small fitness impacts, they are unlikely to promote negative frequency dependence or plant species coexistence in this system. Still, given that pathogen community composition differentiates across host species, some more subtle feedbacks between host relative abundance and pathogen community composition, damage, and fitness impacts are possible, which could, in turn, promote either coexistence or competitive exclusion.

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“…These include Ramularia collo-cygni , a European barley pathogen which emerged in South America in 2011 and which has also recently developed virulence against oats and wheat [12, 13] (Fig. 1).…”

Section: Emerging Pathogensmentioning

confidence: 99%

NOXious gases and the unpredictability of emerging plant pathogens under climate change

Fones

Gurr

2017

BMC Biol

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Emerging pathogens of crops threaten food security and are increasingly problematic due to intensive agriculture and high volumes of trade and transport in plants and plant products. The ability to predict pathogen risk to agricultural regions would therefore be valuable. However, predictions are complicated by multi-faceted relationships between crops, their pathogens, and climate change. Climate change is related to industrialization, which has brought not only a rise in greenhouse gas emissions but also an increase in other atmospheric pollutants. Here, we consider the implications of rising levels of reactive nitrogen gases and their manifold interactions with crops and crop diseases.

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Ramularia collo-cygni—An Emerging Pathogen of Barley Crops

Cited by 78 publications

References 35 publications

The evolutionary history of the current globalRamularia collo-cygniepidemic

The evolutionary history of the current globalRamularia collo-cygniepidemic

Foliar pathogens are unlikely to stabilize coexistence of competing species in a California grassland

NOXious gases and the unpredictability of emerging plant pathogens under climate change

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