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Ramularia leaf spot and Ramularia collo-cygni. A. Typical reddish brown, rectangular lesions surrounded by a chlorotic halo on a winter barley leaf. B. Scanning electron micrograph of R. collo-cygni conidiophores emerging between epidermal cells on the leaf surface of spring barley. C. R. collo-cygni isolate culture grown in vitro for 42 days on potato dextrose agar. D. Late season disease symptoms on spring barley where lesions have coalesced and leaves become senescent reducing photosynthetic leaf area.
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Ramularia leaf spot (RLS) has emerged as a serious threat to barley production across temperate regions of Europe, South America and New Zealand. The disease, typified by characteristic reddish brown, rectangular lesions visible on both sides of the leaf and often ringed by a chlorotic halo is caused by the dothideomycete fungus Ramularia collo-cyg...
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Context 1
... leaf spot (RLS) has emerged as a serious threat to barley production across temperate regions of Europe, South America and New Zealand. The disease, typified by character- istic reddish brown, rectangular lesions visible on both sides of the leaf and often ringed by a chlorotic halo (Fig. 1a) is caused by the dothideomycete fungus Ramularia collo-cygni (Fig. 1b, c). The fungus produces phytotoxins called rubellins (Heiser et al., 2003) in the plant which cause foliar necrosis and reduce photosynthetic area (Fig. 1d). With this reduction in green leaf area, RLS can affect yields by as much as 70%, but losses are more usually ...
Context 2
... (RLS) has emerged as a serious threat to barley production across temperate regions of Europe, South America and New Zealand. The disease, typified by character- istic reddish brown, rectangular lesions visible on both sides of the leaf and often ringed by a chlorotic halo (Fig. 1a) is caused by the dothideomycete fungus Ramularia collo-cygni (Fig. 1b, c). The fungus produces phytotoxins called rubellins (Heiser et al., 2003) in the plant which cause foliar necrosis and reduce photosynthetic area (Fig. 1d). With this reduction in green leaf area, RLS can affect yields by as much as 70%, but losses are more usually in the region of 5-10%. Importantly, RLS can also increase the proportion ...
Context 3
... istic reddish brown, rectangular lesions visible on both sides of the leaf and often ringed by a chlorotic halo (Fig. 1a) is caused by the dothideomycete fungus Ramularia collo-cygni (Fig. 1b, c). The fungus produces phytotoxins called rubellins (Heiser et al., 2003) in the plant which cause foliar necrosis and reduce photosynthetic area (Fig. 1d). With this reduction in green leaf area, RLS can affect yields by as much as 70%, but losses are more usually in the region of 5-10%. Importantly, RLS can also increase the proportion of small grains (screen- ings) by as much as 4% consequently lowering the quality of the grain (Havis et al., 2015). The losses attributed to RLS are ...
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Citations
... In Uruguay, it represents the second most cultivated cereal and is mostly exported as malt (2) . Ramularia leaf spot (RLS), characterized by reddish brown, rectangular lesions on both sides of the leaf, often surrounded by a chlorotic halo (3) , is caused by Ramularia collo-cygni (Rcc (4) ). RLS is a major constraint to production in most barley growing regions, especially in the southern cone of South America (5) . ...
Ramularia leaf spot (RLS) is primarily managed by foliar fungicide spraying, which can result in residues in the grain. In recent years, increasing attention has been paid to the risks these residues pose to consumers. This study aimed to evaluate the efficacy of fungicide management used for RLS control and their fungicide residues in barley grain. Four different alternatives of fungicide mixtures: fluxapyroxad + pyraclostrobin + epoxiconazole; pyraclostrobin + epoxiconazole + chlorothalonil; prothioconazole + trifloxystrobin, and isopyrazam + azoxystrobin, in three spray timings: GS33, GS47 and GS33+GS47, were evaluated in five field experiments. An untreated and a fully protected treatment were included. Fungicide residues, disease severity, control efficacy, area under the disease progress curve, and plump grain yield were calculated. All fungicide strategies adhered to food safety, complying with the Maximum Residue Limits established by Codex and the European Union. Effectiveness varied based on RLS development, application time, and number of applications. Fungicide treatments applied at GS33+GS47 were the most effective as the highest severity levels were observed at the stage after GS47 under the conditions studied. Plump grain yield only showed minimal differences in the late epidemic. The study emphasized the low risk of fungicide presence in grains, favoring efficacy when selecting RLS management options. Any changes in management or regulations should be carefully reviewed to maintain findings. The research underscored the compatibility of recommended fungicide treatments with food safety standards, highlighting the balance between disease control efficacy and consumer safety.
... Ramularia are also well-known and common associates of leaf spot diseases of varying significance in a broad range of plant hosts. For example, Ramularia leaf spots of sugar beet and barley, caused by R. beticola and R. collo-cygni, respectively, are serious emerging disease [140,141]. Species of Ramularia have been reported as endophytes of grapevines [20], while a Ramularia sp. isolated from Rumex gmelini Turcz has been noted to produce the bioactive secondary metabolite chrysophanol [142]. ...
Plant diseases and pests reduce crop yields, accounting for global crop losses of 30% to 50%. In conventional agricultural production systems, these losses are typically controlled by applying chemical pesticides. However, public pressure is mounting to curtail agrochemical use. In this context, employing beneficial endophytic microorganisms is an increasingly attractive alternative to the use of conventional chemical pesticides in agriculture. A multitude of fungal endophytes are naturally present in plants, producing enzymes, small peptides, and secondary metabolites due to their bioactivity, which can protect hosts from pathogens, pests, and abiotic stresses. The use of beneficial endophytic microorganisms in agriculture is an increasingly attractive alternative to conventional pesticides. The aim of this study was to characterize fungal endophytes isolated from apparently healthy, feral wine grapes in eastern Canada that have grown without agrochemical inputs for decades. Host plants ranged from unknown seedlings to long-lost cultivars not widely propagated since the 1800s. HPLC-MS was used to identify unique endophyte-derived chemical compounds in the host plants, while dual-culture competition assays showed a range in endophytes’ ability to suppress the mycelial growth of Botrytis, which is typically controlled in viticulture with pesticides. Twelve of the most promising fungal endophytes isolated were identified using multilocus sequencing and morphology, while DNA barcoding was employed to identify some of their host vines. These fungal endophyte isolates, which consisted of both known and putative novel strains, belonged to seven genera in six families and five orders of Ascomycota. Exploring the fungal endophytes in these specimens may yield clues to the vines’ survival and lead to the discovery of novel biocontrol agents.
... Ramularia are also well-known and common associates of leaf spot diseases of varying significance in a broad range of plant hosts. For example, Ramularia leaf spot of sugar beet and barley, caused by R. beticola and R. collo-cygni, respectively, are serious emerging disease [102,103]. Species of Ramularia have been reported as endophytes of grapevine [16], while a Ramularia sp. isolated from Rumex gmelini Turcz has been noted to produce the bioactive secondary metabolite chrysophanol [104]. ...
Plant diseases and pests reduce crop yields, accounting for global crop losses of 30% to 50%. In conventional agricultural production systems, these losses are typically controlled by applying chemical pesticides. However, public pressure is mounting to curtail agrochemical use. In this context, employing beneficial endophytic microorganisms is an increasingly attractive alternative to the use of conventional chemical pesticides in agriculture. A multitude of fungal endophytes are naturally present in plants, producing enzymes, small peptides and secondary metabolites due to their bioactivity, can protect hosts from pathogens, pests and abiotic stresses. The use of beneficial endophytic microorganisms in agriculture is an increasingly attractive alternative to conventional pesticides. The aim of this study was to characterize fungal endophytes isolated from apparently healthy, feral wine grapes in eastern Canada that have grown without agrochemical inputs for decades. Host plants ranged from unknown seedlings to long-lost cultivars not widely propagated since the 1800s. HPLC-MS was used to identify unique endophyte-derived chemical compounds in the host plants, while dual-culture competition assays showed a range in endophytes’ ability to suppress the mycelial growth of Botrytis, which is typically controlled in viticulture with pesticides. Twelve of the most promising fungal endophytes isolated were identified using multilocus sequencing and morphology, while DNA barcoding was employed to identify some of their host vines. These fungal endophyte isolates, which consisted of both known and putative novel strains, belonged to seven genera in six families and five orders of Ascomycota. Exploring the fungal endophytes in these specimens may yield clues to the vines’ survival and lead to the discovery of novel biocontrol agents.
... In the last four decades, Ramularia leaf spot disease (RLS) became an emerging barley disease and RLS is to date one of the most dominating foliar diseases in many barley growing areas worldwide . RLS disease causes losses in grain yield averaging between 5 and 10%, but occasionally losses reach up to 75% (Pinnschmidt and Jørgensen 2009;McGrann and Havis 2017). The late and rapid appearance of symptoms in the field, relatively fast adaptation of causal Ramularia collo-cygni to fungicides and the lack of fully resistant barley genotypes may have promoted the current dominance of this fungal disease. ...
Ramularia leaf spot disease (RLS) is one of the most dominating fungal diseases in barley. The disease typically appears late in the season after flowering and results in a rapid loss of photosynthetic leaf area. A recent decline in fungicide efficacy and a lack of RLS-resistant cultivars hamper effective control. Global warming will provoke increasing droughts which influence host plant physiology and probably affect outbreak and severity of RLS. Relatively little is known about genetic resistance to RLS in winter barley and about the influence of various weather conditions and climate change on RLS pathogenesis. Hence, we evaluated severity of RLS on 15 winter barley genotypes under persistent late-terminal drought stress or controlled irrigation, respectively, in a field rainout shelter. Over three consecutive years, we observed reproducible differences in quantitative RLS field resistance of the used cultivars and variable suppression of RLS under drought. Our results support a function of drought in suppression of RLS in winter barley, but also reveal strong year effects even under semi-controlled rainout shelter conditions. Data may be relevant for genotype selection in breeding programmes for RLS resistance and for farmers in the frame of integrated disease management under a changing climate.
Graphical abstract
... Twenty-one isolates were obtained from 2012 (n = 2), 2015 (n = 9), and 2017 (n = 10) (Table 1), showing typical Rcc macroscopic features (McGrann et al. 2017), all of which were confirmed as Rcc by the qualitative PCR assay (Fig. 1). Table 2 shows Rcc isolates sensitivity to fungicides between 2012 and 2017. ...
Ramularia leaf spot (RLS) caused by the fungus Ramularia collo-cygni (Rcc) has become a threat to barley production in Argentina. All barley varieties are susceptible to RLS; thus, disease management relies on fungicides like quinone-outside inhibitors (QoIs), demethylation inhibitors (DMIs) and succinate dehydrogenase inhibitors (SDHIs). Europe reported Rcc resistance to fungicides associated with mutations in the fungicide's target genes. The aim of this work was to assess the impact of mutations on sensitivity levels in isolates of Rcc to QoIs, DMIs, SDHIs and a multi-site fungicide used for RLS control in Argentina and others countries. Twenty-one Rcc isolates were collected in the Buenos Aires province in the years 2012, 2015 and 2017 and tested against azoxystrobin (QoI), epoxiconazole and prothioconazole-desthio (DMIs), isopyrazam and fluxapyroxad (SDHIs) and chlorothalonil. For EC50 determination, a sensitivity assay was performed and cytb, cyp51and sdh genes were sequenced for mutation analyses. All isolates showed G143A mutation that confers total resistance to
QoIs (EC50 > 1 mg L−1). Three mutations in the target genes of DMIs (Y403C/S, G404D) were observed. Isolates with both amino-exchanges showed an increase in the EC50 towards DMIs. Mutations B-H266L and C-N87S in the target genes of SDHIs were detected, and both were related to a sensitivity reduction. Mutations occurrence tended to increase from 2012 to 2017 along with higher EC50
values. We found six haplotypes showing that Rcc is potentially adapting to fungicides in Argentina. Efforts must focus on new active ingredients and resistant varieties for a less fungicide-dependent agriculture based on IPM strategies.
... However, in some years the fungus remains in the endophytic stage without producing any disease symptoms [106]. This led to the hypothesis that environmental factors may play a role in the transition from endophytic to necrotrophic growth of R. collo-cygni [107]. Anecdotal reports from barley growers suggested that in years when plants are subjected to waterlogging in the field, RLS symptoms appeared earlier in the growing season compared to years without waterlogging. ...
Dothideomycetes represent one of the largest and diverse class of fungi. This class exhibits a wide diversity of lifestyles, including endophytic, saprophytic, pathogenic and parasitic organisms. Plant pathogenic fungi are particularly common within the Dothideomycetes and are primarily found within the orders of Pleosporales, Botryosphaeriales and Capnodiales. As many Dothide-omycetes can infect crops used as staple foods around the world, such as rice, wheat, maize or banana , this class of fungi is highly relevant to food security. In the context of climate change, food security faces unprecedented pressure. The benefits of a more plant-based diet to both health and climate have long been established, therefore the demand for crop production is expected to increase. Further adding pressure on food security, both the prevalence of diseases caused by fungi and the yield losses associated with abiotic stresses on crops are forecast to increase in all climate change scenarios. Furthermore, abiotic stresses can greatly influence the outcome of the host-pathogen interaction. This review focuses on the impact of abiotic stresses on the host in the development of diseases caused by Dothideomycete fungi.
... Hastalığın arpa bitkisinde tane boyutunda küçülmeye neden olabileceği rapor edilmiştir [10]. Bunun yanı sıra malt kalitesini de etkilemektedir [11,12]. Genel olarak, Ramularia collo-cygni arpa bitkisinde %20-35 arasında verim kaybına yol açmaktadır. ...
... Konukçunun penetrasyonu açık stomalar yoluyla, sporun yaprak yüzeyine tutunması ile başlayan ilk 24 saat içinde gerçekleşmektedir [19]. Ramularia collo-cygni bitkiyi kolonize ederken, fungus gelişimi hücreler arasında olur ve konukçu epidermal hücreleri bozulmaz [11]. Hastalık belirtileri, Ramularia collo-cygni sporulasyon olaylarıyla ilişkilendirilen mezofil dokusunun çökmesinden sonra ortaya çıkmaktadır [26]. ...
... Tohumlar, harici inokulum olmadan kontrollü koşullarda yetiştirildiğinde yapraklarında da fungus tespit edilmiştir [14]. Ramularia yaprak lekesi belirtileri, su basması gibi belirli koşullarda büyüme mevsiminin başlarında ölmekte olan yapraklarda görülebilmektedir [11], ancak RLS belirtileri genellikle çiçeklenme sonrası ortaya çıkmaktadır [18]. ...
Ramularia collo-cygni, arpada (Hordeum vulgare) Ramularia yaprak lekesi hastalığına neden olan fungal bir etmendir. Nekrotik lekelenmeye ve erken yaprak yaşlanmasına neden olarak arpada yeşil yaprak alanı kaybına yol açmakta ve epidemi yapması durumunda %70'e varan verim kaybına neden olmaktadır. Hastalığın geç dönemde ortaya çıkması ve etmenin tanısının zorluğu nedeni ile yüz yıldan fazla süre önce tanımlanmış olmasına rağmen son yıllarda, arpanın önemli bir patojeni olarak kabul edilmiştir. Günümüzde dünya çapında meydana getirdiği epidemiler nedeni ile araştırmacılar tarafından oldukça ilgi görmektedir. Bu derleme, ülkemizde henüz tespiti yapılmamış olan bu fungal etmenin detaylı olarak biyolojisi, epidemiyolojisi, konukçu patojen ilişkilerini tanımlamakta ve mevcut kontrol stratejilerini özetlemektedir.
ABSTRACT Ramularia collo-cygni is a fungal agent that causes Ramularia leaf spot disease on barley (Hordeum vulgare). It causes necrotic spotting and premature leaf aging, leading to loss of green leaf area in barley, and in case of an epidemic, it causes yield loss up to 70%. Although it was defined more than a hundred years ago due to the late emergence of the disease and the difficulty of diagnosis, it has been accepted as an important pathogen of barley in recent years. Today, it attracts a lot of attention by researchers due to the epidemics it creates around the world. This review describes in detail the biology, epidemiology, host-pathogen relationships of this fungal agent, which has not yet been detected in Turkey and summarizes the current control strategies.
... In Finland, Sweden, Denmark, and France, the first records are from the 2000s, and in Estonia, Spain, and Australia, the first records are after 2010 [3]. Since the beginning of 2000, RLS has been considered to be an emerging disease of barley in Europe, South America, and New Zealand [2,4,5]. It is possible that RLS can lead to moderate barley yield losses of 5-20% or greater. ...
... Furthermore, the production of several virulence factors by R. collocygni during leaf infection is probably involved in the development of the symptoms of RLS disease [14]. The visual symptoms of RLS often develop in diseased plants after ear emergence, although, in conducive environmental conditions, symptoms can be detected even sooner [5,15]. ...
... Furthermore, the production of several virulence factors by R. collo-cygni during leaf infection is probably involved in the development of the symptoms of RLS disease [14]. The visual symptoms of RLS often develop in diseased plants after ear emergence, although, in conducive environmental conditions, symptoms can be detected even sooner [5,15]. It is still poorly understood why R. collo-cygni became an aggressive pathogen in most European countries at the beginning of the 2000s. ...
Ramularia leaf spot (RLS), caused by the fungus Ramularia collo-cygni, has recently become widespread in Europe. Succinate dehydrogenase inhibitor (SDHI) and demethylation inhibitor (DMI) fungicides are mainly applied for disease control on barley fields, but pathogen isolates with a reduced sensitivity can cause difficulties. There is an urgent need for new spring barley cultivars that are more resistant to RLS development and can inhibit R. collo-cygni epidemics.
... Over the last years, Ramularia leaf spot (RLS) disease has become one of the most important threats in barley (Hordeum vulgare L.). The causal agent of this late season disease is Ramularia collo-cygni B. Sutton and J.M. Waller which is an important pathogen of barley across many climates (Havis et al., 2015;McGrann & Havis, 2017) and has been detected in barley samples worldwide (Stam et al., 2019). The fungal pathogen causes necrotic leaf spots with the awns and grains also affected. ...
Winter barley (Hordeum vulgare L.) is the third most cultivated crop after corn and wheat in Austria but one of the most challenging for disease control. The foliar pathogen Ramularia collo-cygni B. Sutton and J.M. Waller, causing Ramularia leaf spots (RLS), is one of the most important diseases in barley. In the recent years, control has only been achieved using fungicide mixtures including the multi-site inhibitor chlorothalonil, however this compound is totally banned in the EU. The objective of this study was to assess fungicide dose-rates and spray mixtures for RLS control. Furthermore, a field monitoring within the main barley growing areas of Austria was carried out, to analyse the current resistance situation to DMI and SDHI fungicides, which are still the backbone in RLS control. The results indicate that only the mixture with chlorothalonil achieved a good RLS control. Prothioconazole or benzovindiflupyr (alone or additively) decrease the severity of RLS but increase the local frequency of Cyp51 and sdhC mutations, especially the high dose rates. Based on a low Cyp51 mutation frequency of 16% in untreated control this frequency increased over 3.8 times following an application with 300 g ha−1 prothioconazole. The cumulative-sdhC mutations were even more increased after an application with benzovindiflupyr. This study showed that Ramularia collo-cygni is present in 91% of barley fields presented in this field survey. Widespread use of chlorothalonil fungicide maintained a low to moderate mutation frequency (Cyp51-I325T, Cyp51-I328L, sdhC-H146R and sdhC-H153R) in Austrian barley regions with no increase between 2017 and 2019.
... Barley yields are threatened by various pests and diseases [3]. Ramularia leaf spot (RLS) caused by Ramularia collo-cygni is a late-season disease that has emerged as a major problem in barley production in Europe, South America, and New Zealand over the last 20 years [3][4][5]. The first case of RLS was identified in Estonia 9 years ago in 2012 in a spring barley field [6], but in recent years RLS has become more widespread and is found every season in the majority of the spring and winter barley fields in Estonia. ...
... R. collo-cygni grows initially as an endophyte and after a long latent period, it can then undergo a developmental switch to become an aggressive necrotrophic pathogen, initiated by several factors (e.g., nutrient deficiency, plant senescence) [10][11][12]. In diseased plants, RLS symptoms typically develop after ear emergence, although symptoms can be observed earlier in the season in especially conducive environmental conditions [5,13]. Expression of diverse R. collo-cygni virulence factors at the time of leaf infection is likely to promote RLS disease symptoms [14]. ...
Ramularia leaf spot caused by the fungus Ramularia collo-cygni, has recently become widespread in Estonian barley fields. Currently, disease control in barley fields relies on SDHI and DMI fungicides, which might be threatened by R. collo-cygni isolates that are well-adapted to fungicide pressure. In a two-year study, 353 R. collo-cygni isolates were collected from spring barley fields in Estonia. A total of 153 R. collo-cygni isolates were examined for sensitivity to azoles (DMIs; prothioconazole-desthio, epoxiconazole, mefentrifluconazole) and succinate dehydrogenase inhibitors (SDHIs; boscalid, fluxapyroxad). Epoxiconazole was the least effective and a new fungicide mefentrifluconazole was the most effective DMI. Among SDHIs, fluxapyroxad was more effective than boscalid. Also, single R. collo-cygni isolates with high resistance to tested fungicides occurred, which could affect fungicide control of the pathogen. The entire collection of R. collo-cygni was analysed for mutations in fungicide target proteins. Six mutations were identified in CYP51 gene, the most dominant being I381T, I384T, and S459C. Also, numerous point mutations in the SdhC gene were present. The mutation G143A in strobilurin target protein CytB dominates in over 80% of the R. collo-cygni population, confirming the low efficacy of strobilurin fungicides in barley disease control.
