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Rhynchosporium is one of the main biotic stresses on barley production worldwide. A set of 312 spring barley accessions was tested in four different locations over 3 years, to identify novel genetic resistances to rhynchosporium and to explore the allelic diversity for resistance genes present in this global germplasm collection. High-density genotypes from exome capture and RNA-seq were used to conduct high-resolution association mapping. Seven quantitative trait loci (QTL) were detected, including one in the Rrs2 region, amongst five containing known resistances. Relatively short physical intervals harbouring these resistances were proposed, providing a platform for the identification of underlying genes and tightly linked genetic markers for use in marker assisted selection. Genes encoding kinases were present in four of the QTL, in addition to Rrs1 and Rrs18, two loci known to contribute to rhynchosporium resistance. The frequencies and distributions of these novel and known QTL were superimposed on the regional origin of the landrace genotypes comprising the genome-wide association studies (GWAS) panel, highlighting the value of genetic resources as a source of diverse genetically controlled resistance to rhynchosporium. The detected QTL along with their linked genetic markers, could be exploited either directly for breeding purposes or for candidate gene identification in future studies. [ABSTRACT FROM AUTHOR]

Barley production worldwide is limited by several abiotic and biotic stresses and breeding of highly productive and adapted varieties is key to overcome these challenges. Leaf scald, caused by Rhynchosporium commune is a major disease of barley that requires the identification of novel sources of resistance. In this study two subsets of genebank accessions were used: one extracted from the Reference set developed within the Generation Challenge Program (GCP) with 191 accessions, and the other with 101 accessions selected using the filtering approach of the Focused Identification of Germplasm Strategy (FIGS). These subsets were evaluated for resistance to scald at the seedling stage under controlled conditions using two Moroccan isolates, and at the adult plant stage in Ethiopia and Morocco. The results showed that both GCP and FIGS subsets were able to identify sources of resistance to leaf scald at both plant growth stages. In addition, the test of independence and goodness of fit showed that FIGS filtering approach was able to capture higher percentages of resistant accessions compared to GCP subset at the seedling stage against two Moroccan scald isolates, and at the adult plant stage against four field populations of Morocco and Ethiopia, with the exception of Holetta nursery 2017. Furthermore, four machine learning models were tuned on training sets to predict scald reactions on the test sets based on diverse metrics (accuracy, specificity, and Kappa). All models efficiently identified resistant accessions with specificities higher than 0.88 but showed different performances between isolates at the seedling and to field populations at the adult plant stage. The findings of our study will help in fine-tuning FIGS approach using machine learning for the selection of best-bet subsets for resistance to scald disease from the large number of genebank accessions. [ABSTRACT FROM AUTHOR]

Barley (Hordeum vulgare) is an important crop in Turkey. In this study, 37 barley fields in Batman central district and Beşiri (Batman), Gercüş (Batman), Hasankeyf (Batman), Kozluk (Batman), Sason (Batman), Kocaköy (Diyarbakır), Kurtalan (Siirt), and Midyat (Mardin) districts were examined for the presence of leaf diseases. In addition, 24 naturally grown wild barley (H. spontaneum) populations in Batman central district and Beşiri, Hasankeyf, Kurtalan, and Midyat districts were inspected for the presence of leaf diseases. In barley fields, scald caused by Rhynchosporium commune was the most common disease, followed by the spot form of net blotch caused by Drechslera teres f. maculata, barley stripe caused by Drechslera graminea, the net form of net blotch caused by Drechslera teres f. teres, spot blotch caused by Cochliobolus sativus, powdery mildew caused by Blumeria graminis f. sp. hordei and brown rust caused by Puccinia hordei. Among the Hordeum spontaneum populations the most common disease was scald, followed by the spot form of net blotch, the net form of net blotch, powdery mildew, and brown rust. [ABSTRACT FROM AUTHOR]

Key message: Association analyses of resistance to Rhynchosporium commune in a collection of European spring barley germplasm detected 17 significant resistance quantitative trait loci. The most significant association was confirmed as Rrs1.Abstract: Rhynchosporium commune is a fungal pathogen of barley which causes a highly destructive and economically important disease known as rhynchosporium. Genome-wide association mapping was used to investigate the genetic control of host resistance to R. commune in a collection of predominantly European spring barley accessions. Multi-year disease nursery field trials revealed 8 significant resistance quantitative trait loci (QTL), whilst a separate association mapping analysis using historical data from UK national and recommended list trials identified 9 significant associations. The most significant association identified in both current and historical data sources, collocated with the known position of the major resistance gene Rrs1. Seedling assays with R. commune single-spore isolates expressing the corresponding avirulence protein NIP1 confirmed that this locus is Rrs1. These results highlight the significant and continuing contribution of Rrs1 to host resistance in current elite spring barley germplasm. Varietal height was shown to be negatively correlated with disease severity, and a resistance QTL was identified that co-localised with the semi-dwarfing gene sdw1, previously shown to contribute to disease escape. The remaining QTL represent novel resistances that are present within European spring barley accessions. Associated markers to Rrs1 and other resistance loci, identified in this study, represent a set of tools that can be exploited by breeders for the sustainable deployment of varietal resistance in new cultivars. [ABSTRACT FROM AUTHOR]

Background: Systemic Epichloë endophytes are common fungal symbionts of many cool-season grasses. They are known for their capability of increasing host plant tolerance against biotic and abiotic stressors, including grass pathogens. However, results on endophyte-mediated disease resistance have been ambiguous, and the underlying mechanisms of disease resistance remain unknown. Aims: We studied how Epichloë endophytes affect naturally occurring pathogen, leaf blotch (Rhynchosporium sp.), infections of wild and cultivated tall fescues (Schedonorus phoenix). Methods: Endophytic and endophyte-free tall fescues were grown in a common garden experiment in southern Finland for eight growing seasons. The experimental plants were subjected to nutrient and water treatments. Results: Our results show that the effects of endophytes on leaf blotch infection incidences varied with plant origins and environmental conditions. Overall, the American cultivar 'Kentucky-31ʹ appeared to have less disease symptoms compared to the Finnish cultivar 'Retu' or the wild grasses. Endophytic wild tall fescues from Gotland Island had lower Rhynchosporium incidences than grasses from Åland Islands or coastal Sweden. Conclusions: These results show that Epichloë endophytes can suppress pathogen Rhynchosporium infections in tall fescues, but pathogen resistance depends on grass origin and environmental conditions. [ABSTRACT FROM AUTHOR]

Rhynchosporium commune is a destructive pathogen of barley, causing leaf scald. Previous microsatellite studies used Syria as a representative of cultivated barley's centre of origin, the Fertile Crescent. These suggested that R. commune and Hordeum vulgare (cultivated barley) did not co‐evolve in the host's centre of origin. The present study compares R. commune populations from Syria with those from Iran, which represents a secondary centre of origin for barley at the eastern edge of the Iranian Plateau. Results from this study also suggest that R. commune and barley did not co‐evolve in the centre of origin of cultivated barley. This was evidenced by the low pathogen genetic diversity in Iran, which was even lower than in Syria, indicating that the pathogen may have been introduced recently into Iran, perhaps through infected barley seed. Hierarchical analyses of molecular variance revealed that most genetic diversity in Iran and Syria is distributed within populations, with only 14% among populations. Analyses of multilocus association, genotype diversity and mating type frequency suggest that Iranian populations reproduce predominantly asexually. The presence of both mating types on barley and uncultivated grasses suggest a potential for sexual reproduction. Rhynchosporium commune was also found on Hordeum murinum subsp. glaucum, H. vulgare subsp. spontaneum, Lolium multiflorum and, for the first time, on Avena sativa. The variety of wild grasses that can be infected with R. commune in Iran raises concerns of these grasses acting as evolutionary breeding grounds and sources of inoculum. [ABSTRACT FROM AUTHOR]

Pathogen-associated molecular patterns ( PAMPs) are detected by plant pattern recognition receptors ( PRRs), which gives rise to PAMP-triggered immunity ( PTI). We characterized a novel fungal PAMP, Cell Death Inducing 1 (Rc CDI1), identified in the Rhynchosporium commune transcriptome sampled at an early stage of barley ( Hordeum vulgare) infection., The ability of Rc CDI1 and its homologues from different fungal species to induce cell death in Nicotiana benthamiana was tested following agroinfiltration or infiltration of recombinant proteins produced by Pichia pastoris. Virus-induced gene silencing ( VIGS) and transient expression of Phytophthora infestans effectors Pi AVR3a and Pex RD2 were used to assess the involvement of known components of PTI in N. benthamiana responses to Rc CDI1., Rc CDI1 was highly upregulated early during barley colonization with R. commune. Rc CDI1 and its homologues from different fungal species, including Zymoseptoria tritici, Magnaporthe oryzae and Neurospora crassa, exhibited PAMP activity, inducing cell death in Solanaceae but not in other families of dicots or monocots. Rc CDI1-triggered cell death was shown to require N. benthamiana Brassinosteroid insensitive 1-Associated Kinase 1 (NbBAK1), N. benthamiana suppressor of BIR1-1 (NbSOBIR1) and N. benthamiana SGT1 (NbSGT1), but was not suppressed by Pi AVR3a or Pex RD2., We report the identification of a novel Ascomycete PAMP, Rc CDI1, recognized by Solanaceae but not by monocots, which activates cell death through a pathway that is distinct from that triggered by the oomycete PAMP INF1. [ABSTRACT FROM AUTHOR]

Evolution of fungicide resistance is a major threat to food production in agricultural ecosystems. Fungal pathogens rapidly evolved resistance to all classes of fungicides applied to the field. Resistance to the commonly used azole fungicides is thought to be driven mainly by mutations in a gene ( CYP51) encoding a protein of the ergosterol biosynthesis pathway. However, some fungi gained azole resistance independently of CYP51 mutations and the mechanisms leading to CYP51-independent resistance are poorly understood. We used whole-genome sequencing and genome-wide association studies ( GWAS) to perform an unbiased screen of azole resistance loci in Rhynchosporium commune, the causal agent of the barley scald disease. We assayed cyproconazole resistance in 120 isolates collected from nine populations worldwide. We found that mutations in highly conserved genes encoding the vacuolar cation channel YVC1, a transcription activator, and a saccharopine dehydrogenase made significant contributions to fungicide resistance. These three genes were not previously known to confer resistance in plant pathogens. However, YVC1 is involved in a conserved stress response pathway known to respond to azoles in human pathogenic fungi. We also performed GWAS to identify genetic polymorphism linked to fungal growth rates. We found that loci conferring increased fungicide resistance were negatively impacting growth rates, suggesting that fungicide resistance evolution imposed costs. Analyses of population structure showed that resistance mutations were likely introduced into local populations through gene flow. Multilocus resistance evolution to fungicides shows how pathogen populations can evolve a complex genetic architecture for an important phenotypic trait within a short time span. [ABSTRACT FROM AUTHOR]

Background: The Rhynchosporium species complex consists of hemibiotrophic fungal pathogens specialized to different sweet grass species including the cereal crops barley and rye. A sexual stage has not been described, but several lines of evidence suggest the occurrence of sexual reproduction. Therefore, a comparative genomics approach was carried out to disclose the evolutionary relationship of the species and to identify genes demonstrating the potential for a sexual cycle. Furthermore, due to the evolutionary very young age of the five species currently known, this genus appears to be well-suited to address the question at the molecular level of how pathogenic fungi adapt to their hosts. Results: The genomes of the different Rhynchosporium species were sequenced, assembled and annotated using ab initio gene predictors trained on several fungal genomes as well as on Rhynchosporium expressed sequence tags. Structures of the rDNA regions and genome-wide single nucleotide polymorphisms provided a hypothesis for intra-genus evolution. Homology screening detected core meiotic genes along with most genes crucial for sexual recombination in ascomycete fungi. In addition, a large number of cell wall-degrading enzymes that is characteristic for hemibiotrophic and necrotrophic fungi infecting monocotyledonous hosts were found. Furthermore, the Rhynchosporium genomes carry a repertoire of genes coding for polyketide synthases and non-ribosomal peptide synthetases. Several of these genes are missing from the genome of the closest sequenced relative, the poplar pathogen Marssonina brunnea, and are possibly involved in adaptation to the grass hosts. Most importantly, six species-specific genes coding for protein effectors were identified in R. commune. Their deletion yielded mutants that grew more vigorously in planta than the wild type. Conclusion: Both cryptic sexuality and secondary metabolites may have contributed to host adaptation. Most importantly, however, the growth-retarding activity of the species-specific effectors suggests that host adaptation of R. commune aims at extending the biotrophic stage at the expense of the necrotrophic stage of pathogenesis. Like other apoplastic fungi Rhynchosporium colonizes the intercellular matrix of host leaves relatively slowly without causing symptoms, reminiscent of the development of endophytic fungi. Rhynchosporium may therefore become an object for studying the mutualism-parasitism transition. [ABSTRACT FROM AUTHOR]

Background: The outcome of the arms race between hosts and pathogens depends heavily on the interactions between their genetic diversity, population size and transmission ability. Theory predicts that genetically diverse hosts will select for higher virulence and more diverse pathogens than hosts with low genetic diversity. Cultivated hosts typically have lower genetic diversity and thus small effective population sizes, but can potentially harbour large pathogen population sizes. On the other hand, hosts, such as weeds, which are genetically more diverse and thus have larger effective population sizes, usually harbour smaller pathogen population sizes. Large pathogen population sizes may lead to more opportunities for mutation and hence more diverse pathogens. Here we test the predictions that pathogen neutral genetic diversity will increase with large pathogen population sizes and host diversity, whereas diversity under selection will increase with host diversity. We assessed and compared the diversity of a fungal pathogen, Rhynchosporium commune, on weedy barley grass (which have a large effective population size) and cultivated barley (low genetic diversity) using microsatellites, effector locus nip1 diversity and pathogen aggressiveness in order to assess the importance of weeds in the evolution of the neutral and selected diversity of pathogens. Results: The findings indicated that the large barley acreage and low host diversity maintains higher pathogen neutral genetic diversity and lower linkage disequilibrium, while the weed maintains more pathotypes and higher virulence diversity at nip1. Strong evidence for more pathogen migration from barley grass to barley suggests transmission of virulence from barley grass to barley is common. Conclusions: Pathogen census population size is a better predictor for neutral genetic diversity than host diversity. Despite maintaining a smaller pathogen census population size, barley grass acts as an important ancillary host to R. commune, harbouring highly virulent pathogen types capable of transmission to barley. Management of disease on crops must therefore include management of weedy ancillary hosts, which may harbour disproportionate supplies of virulent pathogen strains. [ABSTRACT FROM AUTHOR]

CYP51 encodes the target site of the azole class of fungicides widely used in plant protection. Some ascomycete pathogens carry two CYP51 paralogs called CYP51A and CYP51B. A recent analysis of CYP51 sequences in 14 European isolates of the barley scald pathogen Rhynchosporium commune revealed three CYP51 paralogs, CYP51A, CYP51B, and a pseudogene called CYP51A-p. The same analysis showed that CYP51A exhibits a presence/absence polymorphism, with lower sensitivity to azole fungicides associated with the presence of a functional CYP51A. We analyzed a global collection of nearly 400 R. commune isolates to determine if these findings could be extended beyond Europe. Our results strongly support the hypothesis that CYP51A played a key role in the emergence of azole resistance globally and provide new evidence that the CYP51A gene in R. commune has further evolved, presumably in response to azole exposure. We also present evidence for recent longdistance movement of evolved CYP5IA alleles, highlighting the risk associated with movement of fungicide resistance alleles among international trading partners. [ABSTRACT FROM AUTHOR]

A family of putative PECTIN ESTERASE INHIBITOR (PEI) genes, which were detected in the genomic region co-segregating with the resistance gene Rrs2 against scald caused by Rhynchosporium commune in barley, were characterized and tested for their possible involvement in mediating resistance to the pathogen by complementation and overexpression analysis. The sequences of the respective genes were derived from two BAC contigs originating from the susceptible cultivar ‘Morex’. For the genes HvPEI2, HvPEI3, HvPEI4 and HvPEI6, specific haplotypes for 18 resistant and 23 susceptible cultivars were detected after PCR-amplification and haplotype-specific CAPS-markers were developed. None of the tested candidate genes HvPEI2, HvPEI3 and HvPEI4 alone conferred a high resistance level in transgenic over-expression plants, though an improvement of the resistance level was observed especially with OE-lines for gene HvPEI4. These results do not confirm but also do not exclude an involvement of the PEI gene family in the response to the pathogen. A candidate for the resistance gene Rrs2 could not be identified yet. It is possible that Rrs2 is a PEI gene or another type of gene which has not been detected in the susceptible cultivar ‘Morex’ or the full resistance reaction requires the presence of several PEI genes. [ABSTRACT FROM AUTHOR]

Seedling reactions of 25 advanced barley lines and 5 barley cultivars to one virulent isolate of Rhychosporium commune were determined under greenhouse conditions. Cultivar Avcı 2002 was found highly resistant and cvs Kalaycı 97 and Bülbül 89 were found susceptible. Barley cultivars Karatay 94 and Efes 3 exhibited a highly susceptible reaction to R. commune. Among the advanced lines, 9 was the most resistant genotype. Barley lines 3, 7, and 11 showed a moderately resistant reaction to the isolate. Genotypes 1, 2, 4, 6, 10, 13, 16, 18, 19, 20, 24, and 25 were susceptible and genotypes 5, 8, 12, 14, 15, 17, 21, 22, and 23 were highly susceptible to the R. commune isolate. Cultivar Avcı 2002 and advanced barley lines 3, 7, 9, and 11 could be used as resistance sources. [ABSTRACT FROM AUTHOR]

The Szum is a right-side tributary of the Tanew River crossing the southern escarpment zone of the Central Roztocze region (SE Poland). Downstream of the strict river break in a section between the 10th and 12th km of the river course in the Szum valley, meadow and peatbog complexes have developed, associated with semi-hydrogenic and marshy soils. In an area of approx. 13 ha of the most valuable non-forest habitats, a variety of plant communities have been identified, including habitats of the Natura 2000 network and habitats that are protected under the Regulation of the Minister of the Environment (2001). These are, for instance, meadow associations Lysimachio vulgaris-Filipenduletum, Lythro-Filipenduletum, Filipendulo ulmariae-Menthetum longifoliae, Angelico-Cirsietum oleracei, and Cirsietum rivularis. The moss-sedge and sphagnum bog communities comprise noteworthy associations Caricetum limosae, Rhynchosporetum albae, Caricetum lasiocarpae, Caricetum paniceo-lepidocarpae, Caricetum davallianae, and Sphagnetum magellanici. These communities are composed of ca. 160 vascular plant species and 40 moss and liverwort species. In 1999-2014, the greatest changes occurred within macroforb meadows, i.e. small Angelico-Cirsietum oleracei and Cirsietum rivularis patches have been transformed into Lysimachio vulgaris-Filipenduletum, while some patches of the latter association have been transformed into a Caricetum acutiformis rush. Several patches of bog-spring associations Caricetum paniceo-lepidocarpae and Carici canescentis-Agrostietum caninae have been irretrievably destroyed. Sphagnetum magellanici appears to be the least stable community among the preserved peatbogs. The changes of meadow and peatbog vegetation observed for the last 15 years are a consequence of natural processes that take place in the river valley and to a large extent human activity connected with the so-called small-scale water retention as well as the presence of a beaver colony in the area and later the abandonment of this area by beavers. Despite the multidirectional changes, the peatbogs of the Szum valley have retained their high species and phytocoenotic diversity, which indicates a substantial degree of naturalness. [ABSTRACT FROM AUTHOR]

The genetic basis of resistance to Rhynchosporium commune was investigated in a winter barley mapping population derived from a cross between cultivars Saffron (moderately susceptible) and Retriever (moderately resistant). Resistance was assessed in field trials through total infection (measured using qPCR), and visible disease symptoms. Phenotypic correlations between both methods of assessing disease severity were high. QTL mapping from three years of field trials identified five significant QTL effects. One QTL effect on chromosome 2H confirms a previously reported resistance from a population derived from the spring cultivar Cocktail and a winter parent derived from the cultivars Pearl and Cocktail. Another QTL effect on 3H corresponds to the reported position of major resistance gene Rrs1. An effect was detected at the mapped position of the semi-dwarfing gene sdw- 1 despite the fact that neither parent has the semi-dwarf phenotype. Of the remaining two QTL effects, one on 6H may represent a previously reported rhynchosporium resistance (QTLRrs6H), whilst the final QTL, represents a novel resistance. In addition, interactions during early infection stages in the parental lines were studied by confocal microscopy of detached leaves inoculated with a GFP-expressing R. commune isolate. This approach identified a number of major differences in fungal growth morphology between the resistant and susceptible parent. [ABSTRACT FROM AUTHOR]

Leaf blotch is a globally important disease of barley crops and other grasses that is caused by at least five host-specialized species in the fungal genus Rhynchosporium. The pathogen R. commune (specialized to barley, brome-grass and Italian ryegrass) has long been considered to reproduce only by asexual means, but there has been accumulating evidence for recombination and gene flow from population genetic studies and the detection of complementary MAT1 -1 and MAT 1-2 isolates in a c. 1:1 ratio in the field. Here, it is demonstrated that 28 isolates of the closely related species R. agropyri (on couch-grass) and R. secalis (on rye and triticale), collected from Europe, were also either of MAT 1-1 or MAT 1-2 genotype and that the distribution of mating types did not deviate significantly from a 1:1 ratio. Evidence is then provided for MAT 1-1-1 and MAT 1-2-1 gene expression during mycelial growth for all three species. By contrast, 27 isolates of the more distantly related R. orthosporum (on cocksfoot) and R. lolii (on Italian and perennial ryegrasses) from Europe were exclusively of the MAT 1-1 genotype, and expression of the MAT 1-1-1 gene could not be detected during mycelial growth. These data suggest that cryptic sexual cycles are more likely to exist for R. commune, R. agropyri and R. secalis than for either R. orthosporum or R. lolii. A phylogenetic analysis of partial MAT 1-1 idiomorph sequences resolved these five species into two distinct groups ( R. commune, R. agropyri and R. secalis versus R. orthosporum and R. lolii) but provided only limited resolution within each group. [ABSTRACT FROM AUTHOR]

Genetic drift and selection are ubiquitous evolutionary forces acting to shape genetic variation in populations. While their relative importance has been well studied in plants and animals, less is known about their relative importance in fungal pathogens. Because agro-ecosystems are more homogeneous environments than natural ecosystems, stabilizing selection may play a stronger role than genetic drift or diversifying selection in shaping genetic variation among populations of fungal pathogens in agro-ecosystems. We tested this hypothesis by conducting a QST/FST analysis using agricultural populations of the barley pathogen Rhynchosporium commune. Population divergence for eight quantitative traits (QST) was compared with divergence at eight neutral microsatellite loci (FST) for 126 pathogen strains originating from nine globally distributed field populations to infer the effects of genetic drift and types of selection acting on each trait. Our analyses indicated that five of the eight traits had QST values significantly lower than FST, consistent with stabilizing selection, whereas one trait, growth under heat stress (22°C), showed evidence of diversifying selection and local adaptation (QST>FST). Estimates of heritability were high for all traits (means ranging between 0.55–0.84), and average heritability across traits was negatively correlated with microsatellite gene diversity. Some trait pairs were genetically correlated and there was significant evidence for a trade-off between spore size and spore number, and between melanization and growth under benign temperature. Our findings indicate that many ecologically and agriculturally important traits are under stabilizing selection in R. commune and that high within-population genetic variation is maintained for these traits. [ABSTRACT FROM AUTHOR]

Detailed knowledge of the evolutionary genetics of virulence is needed to understand and predict host-pathogen dynamics. This study used a virulence assay based on digital image analysis and treated virulence as a quantitative rather than a binary trait. Such quantitative data may better reflect the genetic underpinning of virulence in many pathogen systems and provide better resolution in statistical investigations. A greenhouse experiment based on a common garden design was conducted to measure virulence (% of leaf area covered by lesions) of 126 genetically distinct isolates of the barley scald pathogen, Rhynchosporium commune, originating from nine field populations around the world. Virulence in this pathosystem was found to be a quantitative trait with a continuous distribution in all populations. By comparing population genetic differentiation for virulence and neutral microsatellite markers (i.e. a QST/ GST comparison), evidence that virulence is under stabilizing selection across populations was found. Heritability values were high and ranged from 0·52 to 0·96 with a mean heritability of 0·84. Virulence was positively correlated with spore production as predicted by the trade-off theory of virulence evolution. Furthermore, an association analysis between virulence and sequence haplotypes of three known necrosis-inducing effector genes ( NIP1, NIP2 and NIP3) revealed a significant effect of NIP2 haplotypes and NIP1 deletions. Overall, the results support a quantitative model for virulence in the R. commune-barley pathosystem and very high evolutionary potential for this trait. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report the complete mitochondrial genomes of four closely related fungal species. [•] Three mitochondrial genomes significantly expanded as result of intron invasion. [•] The mitochondrial mutation rate was 77 times higher than the nuclear mutation rate. [•] Our study revealed a very dynamic mitochondrial genome evolution. [Copyright &y& Elsevier]

The fungal genus Rhynchosporium (causative agent of leaf blotch) contains several host-specialised species, including R. commune (colonising barley and brome-grass), R. agropyri (couch-grass), R. secalis (rye and triticale) and the more distantly related R. orthosporum (cocksfoot). This study used molecular fingerprinting, multilocus DNA sequence data, conidial morphology, host range tests and scanning electron microscopy to investigate the relationship between Rhynchosporium species on ryegrasses, both economically important forage grasses and common wild grasses in many cereal growing areas, and other plant species. Two different types of Rhynchosporium were found on ryegrasses in the UK. Firstly, there were isolates of R. commune that were pathogenic to both barley and Italian ryegrass. Secondly, there were isolates of a new species, here named R. lolii, that were pathogenic only to ryegrass species. R. lolii was most closely related to R. orthosporum, but exhibited clear molecular, morphological and host range differences. The species was estimated to have diverged from R. orthosporum ca. 5735 years before the present. The colonisation strategy of all of the different Rhynchosporium species involved extensive hyphal growth in the sub-cuticular regions of the leaves. Finally, new species-specific PCR diagnostic tests were developed that could distinguish between these five closely related Rhynchosporium species. [ABSTRACT FROM AUTHOR]

Diseases of rye (Secale cereale), an important crop in Latvia, might be a risk factor for rye production. The aim of the study was to determine features of rye leaf diseases, to estimate the risk of rye diseases under conditions of Latvia, and to compare various schemes of fungicide treatment that possibly might be useful for integrated disease control. Field trials were carried out from 2009 to 2012 in two locations in Latvia -- State Stende Cereals Breeding Institute and State Priekuļi Plant Breeding Institute. Sixteen trials (two cultivars each year, two sites, and four years) were established during the investigations. Each trial was one-factor design with three variants of fungicide treatment: control (without fungicides), standard treatment during heading (GS 51-55), and DSS (Decision support system). Leaf scald caused by Rhynchosporium secalis and brown rust, caused by Puccinia recondita, were found to be the most important rye diseases during the study. Average additional yield achieved by fungicide application was 8%. Number of rainy days (more than seven, starting from GS 31) was not a sufficient threshold for the control of rye diseases. It was necessary to make assessment of the disease development in the the field. Fungicide application might be necessary if symptoms of leaf scald appear on the youngest leaves after beginning of stem elongation (GS 31-32). [ABSTRACT FROM AUTHOR]

The structure of the commercial fungicide hymexazol, 3-hydroxy-5-methylisoxazol, was transformed to acyloxy, 3-alkoxy, alkylcarbamoyloxy and acylamino derivatives, and their antifungal activities or disease control activities were examined. The 3-acyloxy derivatives were much more active than the other derivatives, and some of the 3-acyloxy derivatives exhibited antifungal activities or disease control activities against a wide range of pathogens, such as Pyrenophora graminea, Alternaria alternata, Cercospora beticola, Rhynchosporium secalis, Septoria tritici, Microdochium nivale, Rhizoctonia solani, Puccinia recondita, and Blumeria graminis. Among them, 5-methyl-3-isoxazolyl (a)-naphthoate and (o)-toluate and 2,2-dichloro-1,3,3-trimethylcyclopropanecarboxylate completely inhibited the mycelial growth of Rhizoctonia solani and M. nivale at 25 mg/L, respectively. [ABSTRACT FROM AUTHOR]

To predict the response of plant pathogens to climate warming, data are needed on current thermal adaptation, the pathogen's evolutionary potential, and the link between them. We conducted a common garden experiment using isolates of the fungal pathogen Rhynchosporium commune from nine barley populations representing climatically diverse locations. Clonal replicates of 126 genetically distinct isolates were assessed for their growth rate at 12°C, 18°C, and 22°C. Populations originatingfrom climates with higher monthly temperature variation had higher growth rate at all three temperatures compared with populations from climates with less temperature fluctuation. Population differentiation in growth rate (QST) was significantly higher at 22°C than population differentiation for neutral microsatellite loci (GST), consistent with local adaptation for growth at higher temperatures. At 18°C, we found evidence for stabilizing selection for growth rateas QST was significantly lower than GST. Heritability of growth rate under the three temperatures was substantial in all populations (0.58-0.76). Genetic variation was lower in populations with higher growth rate at the three temperatures and evolvability increased under heat stress in seven of nine populations. Our findings imply that the distribution of this pathogen is unlikely to be genetically limited under climate warming, due to its high genetic variation and plasticity for thermal tolerance. [ABSTRACT FROM AUTHOR]

Rhynchosporium commune is a haploid fungus causing scald or leaf blotch on barley, other Hordeum spp. and Bromus diandrus. Taxonomy Rhynchosporium commune is an anamorphic Ascomycete closely related to the teleomorph Helotiales genera Oculimacula and Pyrenopeziza. Disease symptoms Rhynchosporium commune causes scald-like lesions on leaves, leaf sheaths and ears. Early symptoms are generally pale grey oval lesions. With time, the lesions acquire a dark brown margin with the centre of the lesion remaining pale green or pale brown. Lesions often merge to form large areas around which leaf yellowing is common. Infection frequently occurs in the leaf axil, which can lead to chlorosis and eventual death of the leaf. Life cycle Rhynchosporium commune is seed borne, but the importance of this phase of the disease is not fully understood. Debris from previous crops and volunteers, infected from the stubble from previous crops, are considered to be the most important sources of the disease. Autumn-sown crops can become infected very soon after sowing. Secondary spread of disease occurs mainly through splash dispersal of conidia from infected leaves. Rainfall at the stem extension growth stage is the major environmental factor in epidemic development. Detection and quantification Rhynchosporium commune produces unique beak-shaped, one-septate spores both on leaves and in culture. The development of a specific polymerase chain reaction ( PCR) and, more recently, quantitative PCR (q PCR) has allowed the identification of asymptomatic infection in seeds and during the growing season. Disease control The main measure for the control of R. commune is the use of fungicides with different modes of action, in combination with the use of resistant cultivars. However, this is constantly under review because of the ability of the pathogen to adapt to host plant resistance and to develop fungicide resistance. [ABSTRACT FROM AUTHOR]

Abstract: Cereal farming is moving rapidly towards reduced tillage, with over 100 million ha of land currently tilled using minimum tillage implements. This study reports five years of data from a field experiment investigating the response of different barley cultivars and mixtures to soil tillage practice and nitrogen fertiliser levels. Five tillage treatments were established that imposed different amounts of soil disturbance: (T1) zero tillage, (T2) minimum tillage to 7cm depth and ploughed treatments followed by power harrowing consisting of (T3) conventional plough to 20cm depth, (T4) plough to 20cm followed by compaction by wheeling the entire plot with a tractor fitted with 8.8 Mg total load and (T5) deep plough to 40cm depth, all on the same site each year. Four winter barley cultivars (Sumo, Fanfare, Pastoral and Pipkin) were selected based on contrasting rooting characteristics, disease resistance and yield sensitivity. They were planted in plots as monocultures and as all 2-, 3- and 4-component mixtures thereof. Significant differences in soil physical properties and carbon content were observed over the five years of the study. Grain yield varied by 13% between tillage treatments, with conventional and deep plough conditions generally the highest yielding and zero tillage the lowest. Sumo gave the highest yield overall under deep plough conditions, whereas Pipkin was the best cultivar under conventional and zero tillage conditions. Rhynchosporium was the most common disease and the mixture gave decreased infection in all years and tillage conditions. Complex mixtures gave around 32% less disease than the simple mixtures. There was an overall differential cultivar response to soil tillage conditions that was buffered by cultivar mixtures. Mixtures offered benefits in both yield response and disease control under all soil tillage conditions. [Copyright &y& Elsevier]

A growth assay was established for the barley pathogen Rhynchosporium commune with EGFP-tagged fungal mutants. This assay was used to study the effect of four antibiotics (hygromycin B, nourseothricin, kanamycin, phleomycin) and a herbicide (phosphinothricin) on fungal development. Fitting the growth curves to the modified Gompertz model allowed calculating growth parameters, such as lag periods of fungal colony formation and mycelial growth rates as well as EC50 values. Except kanamycin all compounds were efficient inhibitors so that the corresponding resistance-conferring genes can be used as markers for selection of fungal transformation-based mutants. In addition the assay was used to quantify the inhibitory activity of a barley secondary metabolite, the indole alkaloid gramine. [ABSTRACT FROM AUTHOR]

Abstract: The effects of field-trial scale, including plot size, and its interaction with fertiliser level and barley germplasm on mixture efficacy in controlling powdery mildew were investigated. Two groups of cultivars, one from cultivars grown in the UK and the other from cultivars grown in Poland, along with all their respective three-component mixtures, were grown in three field trials, one with 13.5m2 plots, one with 0.4m2 plots, and the third in intermediate size plots, which included a mixture of all the cultivars in both groups in equal size treatments of structured spatial arrangements. Another trial utilised similar structured spatial arrangements to trial 3 was carried out using a combination of cultivars with appropriate matching virulence levels (trial 4). Mixtures showed either a reduction in powdery mildew infection compared with the component monoculture mean, or no significant effect. There was a trend towards greater reductions at the low fertiliser level and smaller plot size. The most structured spatial arrangement was most effective for reducing infection in trials 3 and 4, but the complex-homogeneous arrangement in the fourth trial was also effective. Rhynchosporium was reduced by a similar and substantial amount by both spatial treatments in trial 3. The plot size and structuring effects may be explained by the interaction between host heterogeneity structure and pathogen dispersal scale effects, but resource exploitation for yield was best in the complex-homogeneous arrangement in trial 3 where all components were present to respond directly. These findings have implications for methods of trialling mixtures for large-scale field use and for testing component combining ability. [Copyright &y& Elsevier]

Rhynchosporium consists of two species, R. secalis and R. orthosporum. Both are pathogens of grasses with R. secalis infecting a variety of Poaceae hosts and R. orthosporum infecting Dactylis glomerata. Phylogenetic analyses of multilocus DNA sequence data on R. secalis isolates originating from cultivated barley, rye, triticale and other grasses, including Agropyron spp., Bromus diandrus and Hordeum spp., resolved the monophyletic groups into three species according to their respective hosts. Host specificity according to phylogenetic lineages was confirmed with pathogenicity studies. Because R. secalis was described first on rye this name is retained for Rhynchosporium isolates infecting rye and triticale. Rhynchosporium isolates infecting cultivated barley and other Hordeum spp. and Bromus diandrus belong to a distinct species, R. commune. Similarly isolates infecting Agropyron spp. represent a distinct species of Rhynchosporium, namely R. agropyri. A PCR-RFLP assay was developed as a rapid tool for species identification of R. secalis and R. commune. [ABSTRACT FROM AUTHOR]

Both airborne spores of Rhynchosporium secalis and seed infection have been implied as major sources of primary inoculum for barley leaf blotch (scald) epidemics in fields without previous history of barley cropping. However, little is known about their relative importance in the onset of disease. Results from both quantitative real-time PCR and visual assessments indicated that seed infection was the main source of inoculum in the field trial conducted in this study. Glasshouse studies established that the pathogen can be transmitted from infected seeds into roots, shoots and leaves without causing symptoms. Plants in the field trial remained symptomless for approximately four months before symptoms were observed in the crop. Covering the crop during part of the growing season was shown to prevent pathogen growth, despite the use of infected seed, indicating that changes in the physiological condition of the plant and/or environmental conditions may trigger disease development. However, once the disease appeared in the field it quickly became uniform throughout the cropping area. Only small amounts of R. secalis DNA were measured in 24 h spore-trap tape samples using PCR. Inoculum levels equivalent to spore concentrations between 30 and 60 spores per m3 of air were only detected on three occasions during the growing season. The temporal pattern and level of detection of R. secalis DNA in spore tape samples indicated that airborne inoculum was limited and most likely represented rain-splashed conidia rather than putative ascospores. [ABSTRACT FROM AUTHOR]

We examined the variation and relationships between pathogenicity and a microsatellite-based haplotype in 79 Tunisian Rhynchosporium secalis isolates that were collected from the most commonly cultivated barley populations in Tunisia, Rihane cv. and local landraces, with the goal of finding genes that might be used to monitor resistance to scald. Isolates could be classified into three distinct virulence groups based on artificial inoculation of 19 differential cultivars with known scald resistance genes. The resistance gene BRR2 carried by the Astrix differential cultivar appeared to be the most effective in Tunisia. Pathotypes sampled from the Rihane host were more virulent than those sampled from local barley landraces. Because some differential cultivars that carried the same resistance genes showed different reaction patterns to 48 of the isolates, we postulated that other unknown resistance gene(s) specific to Tunisian isolates may be prevalent and could be used in Tunisian barley breeding programs. Microsatellite fingerprinting allowed the detection of 11 alleles linked to the virulence and pathogenic identification of 52% of the tested isolates. Thus, microsatellite analysis may provide a rapid tool for pathogen detection, without an inoculation step that requires long incubation periods before ultimate disease assessment. [ABSTRACT FROM AUTHOR]

Mycochaetophora gentianae, the causal agent of brown leaf spot on gentian ( Gentiana scabra), is characterized by its hyaline besom-like sporophore, although its conidiogenesis and phylogenetic position have so far remained unknown. We isolated the causal fungus from a new host, G. triflora, in Iwate, Japan. Both the G. triflora isolate and the ex-type M. gentianae isolate produced symptoms on G. triflora but not on G. scabra. Microscopic observations of the diseased leaves indicated that conidiogenesis was blastic from short conidiophores, and schizolytic secession of conidia left unthickened and inconspicuous conidial scars on the conidiogenous cells. Conidia were catenate, in branched acropetalous chains; secondary conidia were blastically produced from the first or second cell at the base of primary conidium. The G. triflora isolate was identified as M. gentianae because of its identity to the ex-type in characteristics of culture, pathogenicity, and conidia. Phylogenetic analyses using three ribosomal DNA (rDNA) sequences combined [small subunit (SSU) + large subunit (LSU) + 5.8S rDNA] indicated that both isolates clustered with Rhexocercosporidium carotae, and the cluster was placed within Helotiales–Rhytismatales. Additional analyses using internal transcribed spacers including 5.8S rDNA sequences revealed that both isolates were monophyletic and that they were closely related to three helotialean Pseudocercosporella-like hyphomycetous genera: Helgardia, Rhexocercosporidium and Rhynchosporium. [ABSTRACT FROM AUTHOR]

Two barley populations, i.e. 135 doubled haploid (DH) lines of the cross ‘Igri’ ( rrs1) × ‘Triton’ ( Rrs1) (I × T) and 76 DH lines of the cross ‘Post’ × ‘Vixen’ (both rrs1) (P × V), were analysed to identify QTL for Rhynchosporium secalis resistance independent of the Rrs1 locus by using the single spore R. secalis isolate 271 ( Rrs1-virulent). A major QTL with its positive allele derived from cv. ‘Triton’ was detected in the I × T population on chromosome 2HS explaining almost 80% of the phenotypic variance. Thus, it can be considered as an R-gene corresponding to the already described Rrs15CI8288 on chromosome 2HS. In addition, two minor QTL were identified, one in the centromeric region of 6H in a highly polymorphic region with already several mapped R-genes and a second one at the end of the short arm of chromosome 7H which may be an allele of Rrs2 because of its chromosomal position. Regarding the DH population P × V different minor QTL were identified on chromosomes 6H and 7H. The first one is corresponding to the genomic region of the Rrs13 gene whereas the QTL on chromosome 7H maps in a genomic region where several R-genes against different pathogens have been localized. A comparison of both QTL analyses reveals no R. secalis isolate 271-specific resistance locus but leads to the hypothesis that two of the identified QTL may be alleles of the R-genes Rrs15CI8288 and Rrs2. [ABSTRACT FROM AUTHOR]

Agriculture played a significant role in increasing the number of pathogen species and in expanding their geographic range during the last 10,000 years. We tested the hypothesis that a fungal pathogen of cereals and grasses emerged at the time of domestication of cereals in the Fertile Crescent and subsequently speciated after adaptation to its hosts. Rhynchosporium secalis, originally described from rye, causes an important disease on barley called scald, although it also infects other species of Hordeum and Agropyron. Phylogenetic analyses based on four DNA sequence loci identified three host-associated lineages that were confirmed by cross-pathogenicity tests. Bayesian analyses of divergence time suggested that the three lineages emerged between ∼1200 to 3600 years before present (B.P.) with a 95% highest posterior density ranging from 100 to 12,000 years B.P. depending on the implemented clock models. The coalescent inference of demographic history revealed a very recent population expansion for all three pathogens. We propose that Rhynchosporium on barley, rye, and Agropyron host species represent three cryptic pathogen species that underwent independent evolution and ecological divergence by host-specialization. We postulate that the recent emergence of these pathogens followed host shifts. The subsequent population expansions followed the expansion of the cultivated host populations and accompanying expansion of the weedy Agropyron spp. found in fields of cultivated cereals. Hence, agriculture played a major role in the emergence of the scald diseases, the adaptation of the pathogens to new hosts and their worldwide dissemination. [ABSTRACT FROM AUTHOR]

Rhynchosporium secalis is one of the most destructive pathogens of barley worldwide, causing yield decreases of up to 40% and reduced grain quality. Rhynchosporium is a polycyclic disease. Primary inoculum includes conidia produced on crop debris, infected seeds and possibly ascospores, although these have not yet been identified. Secondary disease spread is primarily by splash dispersal of conidia produced on infected leaves, which may be symptomless early in the growing season. Host resistance to R. secalis is mediated by both ‘major’ or host-specific genes (complete resistance) and ‘minor’ genes of smaller, generally additive effects (partial resistance). Crop growth stage and plant or canopy architecture can modify the expression of resistance. Resistance genes are distributed unevenly across the barley genome, with most being clustered on the short arms of chromosomes 1H, 3H, 6H and 7H, or in the centromeric region or on the long arm of chromosome 3H. Strategies used to manage rhynchosporium epidemics include cultivar resistance and fungicides, and also cultural practices such as crop rotation, cultivar mixtures and manipulation of sowing date, sowing rate or fertiliser rate. However, the high genetic variability of R. secalis can result in rapid adaptation of pathogen populations to render some of these control strategies ineffective when they are used alone. Sustainable control of rhynchosporium needs to integrate major-gene-mediated resistance, partial resistance and other strategies such as customized fungicide programmes, species or cultivar rotation, resistance gene deployment, clean seed and cultivar mixtures. [ABSTRACT FROM AUTHOR]

Plectosporium alismatis is a fungal pathogen that is being investigated as a biocontrol agent for suppressing starfruit (Damasonium minus), a significant weed of Australian rice fields. The aim of this research was to study the effect of the fungus on weed competition and its interactions with chemical herbicides. Conidial germination was significantly reduced by Londax® (bensulfuron-methyl), while MCPA had no effects. Glasshouse trials showed evidence of synergism between the fungus and 1.56% of the recommended dose of Londax®, in reducing the weed growth. The application of inoculum (conidia suspended in water) in the glasshouse eliminated weed competition with rice. In the field, the reduction in weed growth caused by the fungus did not significantly eliminate starfruit competition with rice. This is thought to be due to the presence of other weeds. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the production of chlamydospores and conidia of Rhynchosporium alismatis in a liquid Czapex-Dox based medium supplemented with increasing concentrations of sodium nitrate and malt extract. In addition, the germination of chlamydospores was evaluated. A high concentration of malt extract (4.4 g L -1 ) as the sole carbon source and a high level of sodium nitrate as the sole nitrogen source (3.3 g L -1 ) were shown to increase chlamydospore production while agitation (150 rpm) enhanced conidial yields. Maximum chlamydospore production (2.03×10 5 ±0.7 total chlamydospores mg DW -1 ) was achieved in cultures grown in a medium supplemented with 8.8 g L -1 malt extract and 5.74 g L -1 sodium nitrate. Two days growth was required for maximum chlamydospore and conidial production, while 6 days was necessary to obtain maximum dry weight accumulation (350 mg per flask). Germination of chlamydospores (90%) was significantly higher than germination of conidia (47%) after 2 days growth. [ABSTRACT FROM AUTHOR]

The resistance of barley (Hordeum vulgareL.) toRhynchosporium secalis(scald) has been investigated in two crosses between the susceptible cv.‘Ingrid’ and two resistant Ethiopian landraces,‘Steudelli’ and‘Jet’. Doubled haploids were inoculated in replicated tests using two isolates ofR. secalis,‘4004’ and‘WRS1872’. Expression of resistance differed widely between replicated tests. AFLP, SSR and RFLP markers were used to develop chromosome maps.Results have been analysed using partial least squares regression (PLSR) and interval mapping. In PLSR the major covariance structures or‘latent variables’ between X (markers) and Y (isolates, tests) are modelled as principal components and their optimal number determined by cross-validation. In‘Steudelli’ two QTL were detected, one on each of chromosomes 3H and 7H, in 4 out of 5 tests, while in‘Jet’ only one (different) allele at the 3H locus was found. The validated R2 varied between 11.0% and 64.9% in the replicated tests with‘4004’.With isolate‘WRS1872’ the 7H locus and another 3H locus were detected. By interval mapping the QTL detected were less stable and generally gave lower R2 values than PLSR. PLSR does not depend on maps, but interval mapping based on values predicted by PLSR had R2 around 90%. It is suggested that PLSR may be a useful tool in QTL analysis. [ABSTRACT FROM AUTHOR]

The phytopathogen Rhynchosporium alismatis, occurring on Alisma, Sagittaria and other genera in the Alismataceae, is under investigation as a mycoherbicide for alismataceous weeds in Australian rice crops. The type species of Rhynchosporium, R. secalis, belongs in the Helotiales while the phylogenetic relationships of R. alismatis were unknown. To identify fungi related to R. alismatis, the internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1, 5.8S rRNA gene, ITS2) of 56 isolates was sequenced and compared to those available in databases. Analysis of ITS sequences revealed close relationships between R. alismatis and the teleomorph genus Plectosphaerella, as well as several anamorphic fungi which were primarily species of Verticillium. Rhynchosporium alismatis and Plectosphaerella cucumerina clustered together with 98% bootstrap support. Morphological comparisons supported this relationship indicating that R. alismatis and the anamorphic genus Plectosporium are congeneric. Rhynchosporium alismatis is transferred to Plectosporium, a name proposed for conservation. [ABSTRACT FROM AUTHOR]

The fungal pathogen Rhynchosporium alismatis is being developed for biological control of starfruit ( Damasonium minus ), an important aquatic weed in Australian rice fields. The development of R. alismatis in starfruit differs between juvenile and adult plants. Juvenile starfruit plants are stunted as a result of fungal infection, while in adult plants, the main effect is necrosis and chlorosis of floating leaves. A conidial concentration of 1×10 4 conidia mL -1 was adequate to cause disease symptoms on floating leaves, but the stunting effect on juveniles was caused by concentrations of at least 1×10 5 conidia mL -1 . To successfully inoculate juvenile plants, the water must be drained before inoculation to expose plants to the inoculum. The artificial addition of dew periods did not enhance disease development in plants. The stunting of juvenile starfruit plants caused by the infection of R. alismatis may give rice plants a competitive advantage over the weed at the seedling stage [ABSTRACT FROM AUTHOR]

A partial genetic linkage map was constructed on 71 doubled-haploid lines derived from a cross between the barley lines Tadmor and WI2291 with 181 molecular markers. The segregating population was used to detect markers linked to the geneMlg conferring resistance to powdery mildew (Erysiphe graminis f. sp. hordei) and to genes for quantitative resistance to scald (Rhynchosporium secalis). The gene Mlg on chromosome 4H was flanked by two AFLP markers at a distance of 2.0 and 2.4 cM, respectively. QTLs for resistance to scald were detected on chromosomes 2H and 3H. This association of molecular markers with qualitative and quantitative disease resistance loci represents a valuable starting-point for marker-assisted selection. [ABSTRACT FROM AUTHOR]

Rhynchosporium secalis isolates E97-2 and H97-2, represented the major pathotypes in populations on barley in Alberta, Canada, but differed widely in their virulence. Following greenhouse co-inoculation with the two pathotypes, E97-2, originally isolated from resistant cv. ‘CDC Earl’, predominated over H97-2, isolated from the susceptible cv. ‘Harrington’, from the first to the last of four infection cycles on both ‘CDC Earl’ and ‘Harrington’. These results indicated that the host can rapidly influence pathotype composition and that pathotype E97-2 may have a competitive advantage over H97-2 on these cultivars. DNA polymorphisms were found between isolates from single or mixed inoculations on cvs ‘CDC Earl’ and ‘Harrington’ for four successive cycles. Co-inoculation with the two isolates resulted in a shift to a molecular phenotype more similar to E97-2 than H97-2. The competitive advantage of E97-2 over H97-2, combined with the selective pressure exerted by the host, would explain the increased susceptibility of cv. ‘CDC Earl’ and other cultivars with similar sources of scald resistance, in fields across Alberta. However, H97-2 will likely remain one of the major pathotypes in Alberta due to the relatively large acreage of cv. ‘Harrington’ in this province. [ABSTRACT FROM AUTHOR]

Atypical, green leaf blotch lesions were observed on senescent leaves in winter barley crops and sometimes developed on barley leaves inoculated with conidia of Rhynchosporium secalis in a glasshouse. Similar atypical lesions were induced on barley leaves inoculated with conidia of R. secalis and then grown in controlled environments at 10 °C and 80% rh. Microscopic examination of green lesions from these three sources showed that hyphae of R. secalis had colonized the subsidiary cells of stomata so that guard cells were swollen, resulting in enlarged stomatal pores. Additionally, spore initials bad erupted through the leaf cuticle of some leaves. Most spore initials did not develop into mature conidia when leaves were incubated for 24 h at 20 °C in a closed chamber at 100% rh, but aerial hyphae grew out from the leaf surface. Thus, atypical green lesions produced a much smaller number of spores than typical leaf blotch lesions. [ABSTRACT FROM AUTHOR]

The aim of this investigation was the incorporation of resistance to BaYMV and Rhynchosporium secalis into German winter barley varieties together with the maintenance of their high agronomic characters. The agronomic value of DH-lines after two backcrosses and three haploid steps were compared with the original parents. Lines with similar or superior results could be selected for all the agronomic features evaluated. This method of recurrent selection with repeated haploid steps can therefore lead to the development of lines useful for practical purposes. [ABSTRACT FROM AUTHOR]

Seven winter barley cultivars expressing different field resistance against leaf blotch (Rhynchosporium secalis) and 60 doubled haploid (DLI) lines descending from an F1 hybrid resistant × susceptible were used to develop a test for the quantitative determination of disease severity. Differences in the level of resistance could be measured very precisely after artificial infection of seedlings at the 4-leaf-stage and a subsequent incubation at 7 C. The protein of six isolates was used for antiserum production which was subsequently supplied for serological testing (Enzyme-Linked-lmmunosorbent-Assay) of infected leaves. The results of visible scoring of the seedlings was significantly correlated with measuring with the ELISA reader. The results of the seedling test also corresponded to field scores after natural infection. [ABSTRACT FROM AUTHOR]

In 1992, samples of Rhynchosporium secalis from 19 winter barley crops in England and Wales were examined for carbendazim resistance. Of the 120 isolates obtained, 142% were resistant to carbendazim. A larger survey was carried out in England and Wales in 1993 when samples from 74 crops were examined. On this occasion 1&6% of the 639 isolates obtained were resistant to carbendazim, and resistant isolates were detected in 46% of crops. [ABSTRACT FROM AUTHOR]

Thirty single-spore isolates of Rhynchosporium secalis were assayed in vitro to assess relative sensitivities to the fungicide triadimenol. Minimum inhibitory concentrations ranged from 0.2 to 3.2 μg/ml. Isolates collected in 1981 from winter barley crops treated with triadimenol + fuberidazole, triadimefon, or prochloraz were as sensitive as those from untreated crops, and four isolates collected prior to the widespread use of these fungicides were not especially sensitive. All isolates tested in the greenhouse on winter and spring barley were controlled by Baytan (tria-dimenol and fuberidazole). [ABSTRACT FROM AUTHOR]

This article cites a study that determined the species of Rhynchosporium (R.) occurring on Lolium (L.) multiflorum, their relative frequency, and the host range of common isolates. The variation between and within cultivars was assessed with a view to increasing the level of resistance in L. multiflorum by breeding. R. orthosporum was isolated from L. multiflorum from breeders' plots at Aberystwyth, Wales twice as often as R. secalis. Of 20 genotypes of L. multiflorum, 17 ranked similarly for level of resistance to both pathogen species.

Modern cereal cultivars are highly adapted to, and normally bred and trialled under, high input, high soil disturbance conditions. On-farm conditions are often suboptimal for high yield and frequently use minimal soil tillage, sometimes no-tillage, and therefore, cultivars may be differentially adapted to such conditions. We report a series of trials across 10 years comparing multiple cultivars within years and smaller numbers across years to identify stable cultivars showing preferential adaptation to different levels of soil tillage. Cultivars responded differentially to inversion and non-inversion tillage but were not affected by the level of cultivation within each of these tillage types. Yield declined over time but much more so in the non-inversion tillage treatment. Rhynchosporium symptoms were also increasingly suppressed in the non-inversion tillage type. Several cultivars were identified that showed strong adaptation to tillage type, and some of these were consistent across several trial years. These cultivars can be used to identify traits and genotypes associated with tillage adaptation to target breeding for on-farm conditions. [ABSTRACT FROM AUTHOR]

The reactions of 37 cultivars and two candidate lines of barley to five isolates of Rhynchosporium secalis and their mixtures were determined in assays under greenhouse conditions. Fungal isolates were collected from Ankara province and surrounding areas in Turkey. There were clear differences in the reactions of the cultivars to the fungal isolates and isolates differed in pathogenicity for each cultivar. Of all genotypes tested, seven cultivars (cvs Erginel 90, Şahin 91, Kıral 97, Akhisar 98, Çetin 2000, Çumra 2001, Avcı 2002) and one candidate line (candidate 4) were found to be resistant to all isolates and their mixtures. A5 was found to be the most virulent fungal isolate. [ABSTRACT FROM AUTHOR]