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Barley ‘Scald’ is an economically damaging fungal disease that is a global problem, causing significant yield and economical losses in the UK barley feed and malting industries. Presently, a limited number of Rhynchosporium resistance genes exist, but selective pressures on the fungi cause the demand for new sources of resistance. Landraces, such as the Scottish Bere barley, hold potential sources of resistance that can be utilised, with farmers providing anecdotal evidence of resistance in field populations of Bere. This study analysed 131 heritage cultivars and landrace lines, including 37 Bere lines, to screen for resistance using both detached leaf assays (DLAs) and field experiments. Results showed that Bere lines produced smaller, but more necrotic, lesions for the majority of isolates in the DLAs, as well as smaller scores when visually assessed in field conditions. Whilst the infection patterns of the lines differed between isolates and experimental conditions, three Bere lines were identified as consistently showing reduced levels of infection (45 A 23, 58 A 36 Eday, and 8-125). Using genome-wide association analysis, we were able to identify a number of genomic regions associated with reduced infection symptoms, four in regions associated with known resistance genes, but another four associated with new regions that contain promising candidate genes. Further analysis of these new regions and candidate genes should be undertaken to identify targets for future disease-resistance breeding.

Spermospora avenae causes the economically important red leather leaf disease of oats, which reduces grain yield and hay quality. It was first reported in the USA in 1936 and subsequently in Australia in 1978. Despite this, its phylogenetic placement is unknown, attributed merely to Ascomycota. Twenty-three S. avenae single spore isolates were obtained from affected crops in South Australia and western Victoria from 2008 to 2016. DNA was extracted from each and sequenced using Illumina technology. To identify its closest relatives, a draft genome was de novo assembled and contigs with the highest depth, hypothesised to be the rRNA gene region, were compared to NCBI using the BLASTN function. Contigs that had homologous sequence to the rRNA gene region were used to identify closely related species, which turned out to be Rhynchosporium species. Sequence data from the α-tubulin, β-tubulin, and ITS gene regions of Rhynchosporium species, identified as phylogenetically informative for this genus, were mapped to the S. avenae contigs. Phylogenetic analysis of the ITS region and multilocus concatenation demonstrated that S. avenae is nested within Rhynchosporium, closely related to R. orthosporum and R. lolii. When ITS sequences from other related genera sourced from GenBank were added to the analysis, it appears that Rhynchosporium is paraphyletic and should be split into two genera. Culturally, S. avenae prefers a semi-solid low nutrient medium (ie. ¼ strength PDA made with 1.25% agar) and cool temperature (optimum 15 °C). This corresponds well with the cold wet seasonal conditions required for disease development in the field.

Тhe features of the formation of phytopathogenic fond of micromycetes, pathogens of cereal diseases of the right-bank Forest-steppe of Ukraine for 2004– 2019 are analyzed. The leading place in the phytopathogenic complex is occupied by micromycetes, among which the pathogens of root rot and powdery mildew dominate. The area of crops affected by these diseases is 32.5–75.0%, and in some years reaches to 100%, the spread of diseases — 4.2–19.8%, the development of diseases — 1.6–14.0%. In addition, leaf septoria and pyrenophorosis predominate in agrocenoses of winter wheat, at spring wheat — dark brown spotting; spring barley — spotting and rhynchosporium. Olive mold and fusariosis dominate among the diseases of the head. During the study period, a significant development of winter wheat pyrenophorosis was noted — 5.1–16.8% (max 35%), brown leaf rust spread on spring wheat — 4.6–24.4% (max 45%) and spread of spotting of spring barley — up to 50% (max 100%). Exceeding the threshold of harmfulness of root rot (in 2.8–4.0 times), powdery mildew of wheat (in 6.3– 8.2 times) and spotting of barley (in 2.5 times) leads to excessive use of fungicides and causes increased environmental risks in agrocenoses, chemical and biological pollution of agroecosystems, which significantly affects the quality and safety of products.

The analysis of the phytosanitary situation in production, selection and seed crops of winter rye in Kirov region for the period from 1999 to 2018 was carried out in order to adjust the tasks of breeding for resistance to the most harmful diseases. The affection of the sowings (spread of the disease), the development of the disease and the area of the affected crops relative to the number of the examined ones were evaluated. The trend in the development of the diseases was established on the basis of a regression analysis of long-term data of the branch of the FSBI Rosselkhozcentr in Kirov region. The annual (100 %) manifestation of snow mold and ergot has been established. Next according to the frequency of manifestation there are root rots and brown rust – 95 %, powdery mildew – 75 %, sclerotinia – 70 %, Fusarium head blight – 70 %, and stem rust – 50 %. A relatively low frequency of manifestation has been observed with septoriose and rhynchosporium – 35 and 30 %. However, taking into account the development of winter rye diseases which exceed the economic threshold of harmfulness (ETH), the studied pathocomplexes have different levels of danger. Thus, the development of brown rust above ETH was diagnosed 13 times within 19 years. The most severe disease development (20.0-52.0 %) was in 2001, 2005, 2009, and 2010; weak - in 2007 (0.8 %), 2017 (1.4 %), 2015 (2.4 %), and 2011 (5 %). The manifestation of powdery mildew above ETH was observed 6 times within 15 years, disease development was at the level of 13.0-53.0 %. The development of septoriose above ETH was diagnosed 6 times within 7 years with the development of disease from 13.5 to 63.0 %. Development of stem rust above ETH was diagnosed 5 times within 10 years with the status of the sign of 15.0-20.0 %. The cyclicity of spread of the most harmful diseases and trends of their change in agrocenoses of winter rye are shown. Thus, the most epitphytotically dangerous diseases include snow mold, brown rust, stem rust, powdery mildew and septoriose. Constant control is also required in relation to ergot and Fusarium head blight. These diseases should be an object for breeding-and-immunological studies.

There are five described Rhynchosporium species, Rhynchosporium commune, R. secalis, R. agropyri, R. orthosporum and R. lolii, that cause scald diseases on Poaceae. This study used morphological (conidial shape and size) and phylogenetic analyses of two loci (the internal transcribed spacer region (ITS) and β-tubulin (TUBB)) to identify Rhynchosporium species and their host ranges in Iran. Despite the large variation observed for Rhynchosporium conidial dimensions, the phylogenetic analyses of the ITS region and concatenated ITS and TUBB loci revealed that all isolates from wild grasses in Iran belong to R. commune. R. commune was isolated from Hordeum murinum ssp. glaucum, Hordeum vulgare ssp. spontaneum, Lolium multiflorum and Avena sativa in Iran. A. sativa has only been reported from Iran as a host for R. commune. After cross inoculation, A. sativa was considered as the most resistant host showing the lowest susceptibility to R. commune isolates. Of the grass hosts tested, H. vulgare ssp. spontaneum was the most susceptible. The most aggressive isolate across all tested hosts was isolated from Hordeum murinum ssp. glaucum. Cross-infection of the R. commune isolates from all hosts onto uncultivated grasses and cultivated barley suggests the potential of the uncultivated grasses as inoculum sources for cultivated barley epidemics and pathogen evolution. Thus, management of uncultivated grasses in the vicinity of barley fields should assist in managing the disease on cultivated barley.

Diagnostic markers for Rrs1Rh4 have been identified by testing for associations between SNPs within the Rrs1 interval in 150 barley genotypes and their resistance to Rhynchosporium commune isolates recognised by lines containing Rrs1. Rhynchosporium or barley scald, caused by the destructive fungal pathogen Rhynchosporium commune, is one of the most economically important diseases of barley in the world. Barley landraces from Syria and Jordan demonstrated high resistance to rhynchosporium in the field. Genotyping of a wide range of barley cultivars and landraces, including known sources of different Rrs1 genes/alleles, across the Rrs1 interval, followed by association analysis of this genotypic data with resistance phenotypes to R. commune isolates recognised by Rrs1, allowed the identification of diagnostic markers for Rrs1Rh4. These markers are specific to Rrs1Rh4 and do not detect other Rrs1 genes/alleles. The Rrs1Rh4 diagnostic markers represent a resource that can be exploited by breeders for the sustainable deployment of varietal resistance in new cultivars. Thirteen out of the 55 most resistant Syrian and Jordanian landraces were shown to contain markers specific to Rrs1Rh4. One of these lines came from Jordan, with the remaining 12 lines from different locations in Syria. One of the Syrian landraces containing Rrs1Rh4 was also shown to have Rrs2. The remaining landraces that performed well against rhynchosporium in the field are likely to contain other resistance genes and represent an important novel resource yet to be exploited by European breeders.

Plant pathogens secrete effector proteins to manipulate the host and facilitate infection. Cognate hosts trigger strong defence responses upon detection of these effectors. Consequently, pathogens and hosts undergo rapid coevolutionary arms races driven by adaptive evolution of effectors and receptors. Because of their high rate of turnover, most effectors are thought to be species-specific and the evolutionary trajectories are poorly understood. Here, we investigate the necrosis-inducing protein 1 (NIP1) effector in the multihost pathogen genus Rhynchosporium. We retraced the evolutionary history of the NIP1 locus using whole-genome assemblies of 146 strains covering four closely related species. NIP1 orthologues were present in all species but the locus consistently segregated presence-absence polymorphisms suggesting long-term balancing selection. We also identified previously unknown paralogues of NIP1 that were shared among multiple species and showed substantial copy-number variation within R. commune. The NIP1A paralogue was under significant positive selection suggesting that NIP1A is the dominant effector variant coevolving with host immune receptors. Consistent with this prediction, we found that copy number variation at NIP1A had a stronger effect on virulence than NIP1B. Our analyses unravelled the origins and diversification mechanisms of a pathogen effector family shedding light on how pathogens gain adaptive genetic variation.

Cultivar mixtures of winter barley and spring barley, together with their component monocultures, were grown in field trials to assess the effect of cultivar combinations on both straw and grain yield. The overall grain yields for all trials were significantly higher for the cultivar mixtures than for the corresponding component monocultures. Also, significant decreases in rhynchosporium disease severity for cultivar mixtures were recorded for most non-fungicide treatments. The size of these responses was often significantly correlated with the component number of the mixtures. The amount of straw produced in mixtures was sometimes changed significantly, but not always in a positive direction and it was only correlated with increasing mixture component number in two environments. No correlation of straw yield potential of cultivars with performance in mixtures was found. Cultivar × cultivar mixture × environment interactions appeared to affect the relative yield of grain and straw differentially and therefore it was not possible to predict the effect of mixtures on the harvest index.

Summary • Winter wheat (Triticum aestivum) and winter barley (Hordeum vulgare) were grown on soil contaminated with different levels of a marked bacterial potato pathogen Erwinia carotovora ssp. atroseptica (Eca) from a previous blackleg-infected potato crop, to determine whether the presence of this pathogen could affect disease development on wheat and barley. • The diseases ‘septoria leaf blotch’ and ‘powdery mildew’ on wheat (caused by Septoria tritici and Blumeria graminis f. sp. tritici, respectively) and ‘scald’ or ‘rhynchosporium’ on barley (caused by Rhynchosporium secalis) were assessed over two growing seasons, and the presence of the marked Eca strain monitored. • Wheat diseases were greater on the areas with high levels of Eca contamination than on areas with low-level contamination. Rhynchosporium on barley was not affected overall, although it decreased on the high-level contamination areas early in the season. The Eca strain was detected on the upper foliage of both wheat and barley. • Increased S. tritici symptoms in the field may be due to ‘synergistic’ interactions between the Eca and the fungal mycelium, as reported in previously published laboratory experiments. The potential importance of such fungal–bacterial interactions is discussed.

The article is devoted to the effect of biofertilizers (Bioklad and Vermix) on the severity of common diseases of spring barley in field trials conducted in the Orel region. The authors estimate risks of spring barley diseases and analyse the results of the three-year experiment, carried out under certain weather and climate conditions. The subject of the research is the spring barley crop Suzdalets under intensive farming (zoned for 2, 3, 5 regions of Russia). For a more comprehensive assessment, the experimental process includes separate and combined application of biofertilizers at two different doses. The results of the experiment shows that spring barley crops have responded to all tested combinations of treatment and, at the same time, biofertilizers Bioklad and Vermix, regardless of the doses of application used, had a positive treatment effect and reduced development of severe plant diseases such as root rot by 8.4%, Helminthosporium spot by 29.2%, powdery mildew by 28.9%, Rhynchosporium by 26.3%, stem rust by 65.9%, Septoria spot by 24.4%, and Fusarium head blight by 12%. The most productive agrocenosis of spring barley was formed with the use of Bioklad: barley yield was 0.59 t/ha at a dose of 1 L/ ha and 0.61 t/ha at a dose of 2 L/ha.

The disease pressure from Pyrenophora teres, Rhynchosporium graminicola, and Ramularia collo– cygni varies widely between years and locations, which highlights the need for using risk models to avoid unnecessary use of fungicides. Three disease risk models were tested in thirty– three field trials during two seasons in five countries in order to validate and identify situations favourable for barley leaf blotch diseases in the Nordic–Baltic region. The tested models were: The Crop Protection Online (CPO), which uses number of days with precipitation (>1 mm), cultivar resistance and disease data as basis for risk assessments; the humidity model (HM) which signals a risk warning after 20 continuous hours with high humidity, and the Finnish net blotch model (WisuEnnuste), which calculates a risk based on previous crop, tillage method, cultivar resistance and weather parameters. The risk models mostly gave acceptable control of diseases and yield responses compared with untreated and reference treatments. In the dry season of 2018, the models recommended 88–96% fewer applications than the reference treatments, while in 2019, the number of applications was reduced by 0–76% compared to reference treatments. Based on yield increases, the recommendations were correct in 50–69% of the trials compared to one–treatment references and 69–80% of the trials when references used mainly two treatments.

The taxonomy of Oculimacula, Rhynchosporium and Spermospora is re-evaluated, along with that of phylogenetically related genera. Isolates are identified using comparisons of DNA sequences of the internal transcribed spacer ribosomal RNA locus (ITS), partial translation elongation factor 1-alpha (tef1), actin (act), DNA-directed RNA polymerase II largest (rpb1) and second largest subunit (rpb2) genes, and the nuclear ribosomal large subunit (LSU), combined with their morphological characteristics. Oculimacula is restricted to two species, O. acuformis and O. yallundae, with O. aestiva placed in Cyphellophora, and O. anguioides accommodated in a new genus, Helgardiomyces. Rhynchosporium s. str. is restricted to species with 1-septate conidia and hooked apical beaks, while Rhynchobrunnera is introduced for species with 1-3-septate, straight conidia, lacking any apical beak. Rhynchosporium graminicola is proposed to replace the name R. commune applied to the barley scald pathogen based on nomenclatural priority. Spermospora is shown to be paraphyletic, representing Spermospora (type: S. subulata), with three new species, S. arrhenatheri, S. loliiphila and S. zeae, and Neospermospora gen. nov. (type: N. avenae). Ypsilina (type: Y. graminea), is shown to be monophyletic, but appears to be of minor importance on cereals. Finally, Vanderaaea gen. nov. (type: V. ammophilae), is introduced as a new coelomycetous fungus occurring on dead leaves of Ammophila arenaria., Fungal Systematics and Evolution, 7 (1)

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.

Fungal plant diseases driven by weather factors are common in European wheat and barley crops. Among these, septoria tritici blotch (Zymoseptoria tritici), tan spot (Pyrenophora tritici-repentis), and stagonospora nodorum blotch (Parastagonospora nodorum) are common in the Nordic-Baltic region at variable incidence and severity both in spring and winter wheat fields. In spring barley, net blotch (Pyrenophora teres), scald (Rhynchosporium graminicola, syn. Rhynchosporium commune) and ramularia leaf spot (Ramularia collo-cygni) are common yield limiting foliar diseases. We analysed data from 449 field trials from 2007 to 2017 in wheat and barley crops in the Nordic-Baltic region and explored the differences in severity of leaf blotch diseases between countries and years, and the impact of the diseases on yield. In the experiments, septoria tritici blotch dominated in winter wheat in Denmark and southern Sweden; while in Lithuania, both septoria tritici blotch and tan spot were common. In spring wheat, stagonospora nodorum blotch dominated in Norway and tan spot in Finland. Net blotch and ramularia leaf blotch were the most severe barley diseases over large areas, while scald occurred more locally and had less yield impact in all countries. Leaf blotch diseases, with severity >50% at DC 73–77, caused an average yield loss of 1072 kg/ha in winter wheat and 1114 kg/ha in spring barley across all countries over 5 years. These data verify a large regional and yearly variation in disease severity, distribution and impact on yield, emphasizing the need to adapt fungicide applications to the actual need based on locally adapted risk assessment systems.

Systemic Epichloe 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, in...

With the threat of certain plant protection products becoming ineffective due to reduced pathogen sensitivity to fungicides or through the removal of products due to changes in legislation, alternative compounds are sought for use in disease management programmes. The effects of an arabinoxylan film-forming polymer derived from maize cell walls to control crop diseases of spring barley was assessed in field experiments. Control of powdery mildew, Rhynchosporium scald, and Ramularia leaf spot on barley was achieved with the polymer but control was inconsistent between trials. However, good levels of disease control were observed when the polymer was applied with a reduced fungicide programme. No yield penalties were associated with use of the polymer in any trial irrespective of the level of disease control. Alternative plant protection products such as this arabinoxylan polymer may be useful components in future integrated disease management strategies aimed at reducing fungicide inputs without any cost to disease control.

The National Centre for Plant Genetic Resources (NCPGRU) formed a genetic collection of spring barley comprising 315 accessions from 25 countries with identified genes of resistance to major diseases, which is of practical value for breeding. The aim and tasks of the study was to analyze literature, to estimate the new gene pool of spring barley, to systematize and select accessions, to form a genetic collection by resistance to disease. Materials and methods. The study material was spring barley collection accessions. The genetic collection of spring barley includes 114 reference accessions. Results and discussion . Multi-year field studies revealed highly resistance to powdery mildew in accessions carrying genes Ml-a3; Ml-g; Ml-a13; Ml-a12 (Reg1t12) reg 6e; Ml- (la), Ml-a7; Ml-k; Reg 1g7; Reg 4ac; Reg 2ac . 7-9 point resistance to dwarf rust was determined by genes Rph12 and Rph3. Genes Un2; Run3; Un-3, Un4, Un5, Un6, rh6, and rh7 were effective against loose smut in our environment. Resistance to rhynchosporium leaf scald was observed in accessions with genes Rh4; Rh-1 . Conclusions. As a result of multi-year studies, the genetic collection by resistance to diseases, which comprises 315 accessions with 113 expression levels carrying 86 gene groups, was formed. It can substantially cover breeding needs for developing modern spring barley varieties that would be resistant to powdery mildew, dwarf rust, loose smut and rhynchosporium leaf scald. Among accessions, we also found sources of valuable traits, in particular, of high 1000-grain weight (Maris Concord – 49.1 g; Harry – 49.3 g; Medina – 49.0 g; Delita – 49.8 g; and Quantum Plus - 50.3 g) and of high yield capacity (Regatta - 780 g/m 2 ; Tennis - 900 g/m 2 ; Keti - 790 g/m 2 ; Jarek - 815 g/m 2 ; and Femina - 820 g/m 2 ). Use of collection accessions with identified genes will improve the breeding efficiency and accelerate breeding under the conditions of the Forest-Steppe of Ukraine

Cultivars and some cultivar mixtures of spring barley were grown under inversion and non-inversion tillage conditions for three or four years and assessed for disease and yield in order to obtain genotypes that can be used to determine the mechanisms of cultivation adaptation. In general, the higher-yielding cultivars under inversion tillage conditions gave lower yields under non-inversion tillage, whereas low-yielding older cultivars showed relatively smaller reductions in yield under non-inversion tillage. A few cultivars showed preferential yield performance for either inversion or non-inversion tillage and this was irrespective of their overall yield performance. There was no pedigree or breeding programme link between these cultivars and no above-ground gross morphological trait observed was associated with tillage adaptation. Root hairs may contribute to inversion tillage adaptation as a root hair absence mutant was associated with non-inversion adaptation and it is likely that other root-associated traits are responsible also for tillage adaptation. There was no overall cultivar or tillage interaction with rhynchosporium symptoms but a differential tillage interaction may occur in individual years. We have identified clearly contrasting cultivars and tested their across-season robustness with respect to tillage treatment for further detailed mechanistic studies and identification of tillage adaptation traits.

Integrated Pest Management (IPM) offers a suite of ways by which to reduce the need for pesticide use, thus minimising environmental damage and pathogen resistance build-up in crop production. Farmers and agronomists active in the Scottish spring barley sector were surveyed to determine the extent to which they currently use or are open to implementing three IPM measures – varietal disease resistance, crop rotation, and forecasting disease pressure – in order to control three important fungal diseases. Overall, the survey results demonstrate that farmers and agronomists are open to using the three IPM techniques. However, gaps between actual and perceived recent practice were large: despite over 60% of farmers stating that they sowed varieties highly resistant to Rhynchosporium or Ramularia, less than one third of reportedly sown varieties were highly resistant to these diseases. Similarly, over 80% of farmers indicated that they used crop rotations, yet 66% of farmers also reported sowing consecutive barley often/always. Further research is needed in order to understand why these gaps exist, and how they can be reduced in future in order to increase IPM uptake and optimise pesticide use.

Major resistance gene to rhynchosporium, Rrs18, maps close to the telomere on the short arm of chromosome 6H in barley. Rhynchosporium or barley scald caused by a fungal pathogen Rhynchosporium commune is one of the most destructive and economically important diseases of barley in the world. Testing of Steptoe × Morex and CIho 3515 × Alexis doubled haploid populations has revealed a large effect QTL for resistance to R. commune close to the telomere on the short arm of chromosome 6H, present in both populations. Mapping markers flanking the QTL from both populations onto the 2017 Morex genome assembly revealed a rhynchosporium resistance locus independent of Rrs13 that we named Rrs18. The causal gene was fine mapped to an interval of 660 Kb using Steptoe × Morex backcross 1 S2 and S3 lines with molecular markers developed from Steptoe exome capture variant calling. Sequencing RNA from CIho 3515 and Alexis revealed that only 4 genes within the Rrs18 interval were transcribed in leaf tissue with a serine/threonine protein kinase being the most likely candidate for Rrs18.

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. Postprint

Use of multiline crop cultivars enhances guaranteed production, besides managing disease pathogens. However, the exact mode of action on disease pathogens is not well understood. Management of air-borne disease pathogens (Septoria spp., Helminthosporium spp., Rhynchosporium spp., and Pseudocercosporella herpotrichoides), soil-borne disease pathogens (Helminthosporium victoria, Rhizoctonia solani, Pseudocercosporella herpotrichoides, Phytophthora sojae, and Cephalosporium gramineum), viral diseases (oat yellow dwarf, wheat mosaic), and multiple diseases by using multiline crop cultivars have been discussed in this chapter. Management of insect pests (corn leafhopper, oat aphids, and leafhoppers on potato, cabbage, and lima bean) and weeds are also discussed.

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 (QTLTritonRrs6H271), 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.

The use of chemical fertilizers have been negative impact on environment, especially in increased the gas emissions and reduced the diversity of microbes, such as bacteria, actinomycetes, and soil fungi. As the one of the alternatively is used the combined compost. For instance, grass compost with the added of inorganic fertilizer (chemical), oil palm empty fruit bunches compost with the added of inorganic fertilizer, and the inorganic fertilizer without compost. The measuring of gas emissions was carried out on CH4, CO2 and N2O at several of the oil palm planting holes. Every sample gases were collected by the chambers installed with syringe. .Thus, the gas emissions were analyzed by chromatography gas type GHG 450 Shimadzu. Besides that, the diversity of soil fungi were also determined by the characterization and identification. The result of this research showed of reducting on CH4 that was appplied by the combined of oil palm empty fruit bunch compost with inorganic fertilizers i.e., 0.019 until-0.316 g CH4.m-2.h-1. The same patterns were also demonstrated by CO2 from the treament of oil palm empty fruit bunch with inorganic fertilizers, viz 755.246 untill-2.331 g CO2.m-2.h-1. Relating to N2O, it has undergone reduced by grass compost with inorganic fertilizers, viz-27.726 until-25.622 mg N2O.m-2.h-1 . Meanwhile, the genera of soil fungi that were found on the sites after applying combining compost, viz Aspergillus, Bipolaris, Gonatobotrys, Gonatorrhodiella, Oidiodendron, Penicillium, Rhynchosporium, Rhizopus, Trichoderma, and Trichocladium. Therefore, the use of compost with combining chemical fertilizers are potentially to apply into the oil palm field on wetlands.

Field experiments were conducted over two years to quantify the yield response to fungicide of spring barley ( Hordeum vulgare L.) genotypes differing in disease severity and canopy structure. Fourteen genotypes were selected from a doubled-haploid mapping population to represent three distinct canopy phenotypes; tall with prostrate leaves, medium height with prostrate leaves and medium height with erect leaves. The fungicide treatments were based on a triazole plus strobilurin and chlorothalonil programme applied at the start of stem extension and during booting. Untreated plots served as controls. The major foliar diseases and disorders were powdery mildew and brown spotting in 2006 and powdery mildew, rhynchosporium barley leaf blotch and brown spotting in 2007, and genotypes differed significantly in the severity of each. Fungicide reduced powdery mildew and rhynchosporium symptoms in susceptible genotypes, but had little effect on spotting. The yield response to fungicide averaged across genotypes was approximately 1 t ha −1 and there was no significant difference in response between canopy types or genotype. The increase in yield was mostly via an increase in grain numbers m −2 with smaller or non-significant effects of fungicide on mean grain weight. When effects of fungicide on radiation interception were plotted against those on yield, a yield response of 0.8–1.4 t ha −1 was indicated in the absence of visible disease. The results show that the effects of fungicide treatment on grain numbers cannot be explained just in terms of protection of green area and increase in radiation interception. Nor were they the result of a delay in leaf senescence. Other possible explanations include control of symptomless infection at critical developmental stages, or direct effects of fungicides on plant metabolism. These findings have important implications for fungicide stewardship and disease management in barley, because the requirement for fungicide, as defined in terms of the likely yield response of the crop, cannot be predicted just from an assessment of the amount visible disease present or the risk of a disease epidemic developing.

Summary 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 (qPCR) 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.

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 7 cm depth and ploughed treatments followed by power harrowing consisting of (T3) conventional plough to 20 cm depth, (T4) plough to 20 cm followed by compaction by wheeling the entire plot with a tractor fitted with 8.8 Mg total load and (T5) deep plough to 40 cm 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.

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 13.5 m 2 plots, one with 0.4 m 2 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.

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.

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 MAT1-2 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 MAT1-1 or MAT1-2 genotype and that the distribution of mating types did not deviate significantly from a 1:1 ratio. Evidence is then provided for MAT1-1-1 and MAT1-2-1 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 MAT1-1 genotype, and expression of the MAT1-1-1 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 MAT1-1 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.

Ramularia leaf spot and Rhynchosporium leaf scald are two of the major diseases of barley crops in cooler temperate countries. The methods below are aimed at the identification and quantification of fungal DNA in leaf samples but can also be used for pathogen detection from seed or DNA extracted from environmental samplers. The methods describe in detail two individual quantitative PCR tests. The successful multiplexing of assays will lead to faster throughput of samples.

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.

Solar radiation, particularly its UV wavelengths, greatly influences conidium survival and this study looked at the impact of radiation and its interactions with temperature on Plectosporium alismatis and Colletotrichum orbiculare, two fungi that are potential mycoherbistats. UV radiation, rather than temperature, was found to be the primary cause of conidium mortality; however, there were interactions between these factors leading to the enhancement of the lethal effects of UVB on conidium germination at high temperatures. C. orbiculare was more sensitive than P. alismatis with conidium germination being halved by UVB doses of 1.47 and 13.1 kJ m−2, respectively, for the two pathogens. Conidium mortality was dose-dependent and for P. alismatis exposed to a dose of 3.7 kJ m−2 reciprocity was observed. However, for C. orbiculare equivalent doses were not reciprocal as higher doses for short periods were more lethal than lower doses of longer duration. Low UVB doses only caused delays in conidium ge...

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.

To prolong the effective life of the newer, more active DeMethylation Inhibitor (DMI) fungicides, two-spray programmes were evaluated for their effectiveness in combining good control of rhynchosporium on winter barley with prevention of the build-up of DMI-resistant pathogen strains. Programmes were based on the DMI epoxiconazole alone or in combination or alternation with three partner fungicides with different modes of action, fenpropimorph (a morpholine), cyprodinil (an anilinopyrimidine), azoxystrobin (a QoI/strobilurin fungicide). In the majority of six field trials in Northern Ireland and South-west England (1998–2000), DMI sensitivity of Rhynchosporium secalis isolates was lower after fungicide treatment than before and the least sensitive isolates came from the plots treated with two half-rate applications of epoxiconazole alone. All fungicide programmes reduced disease compared with the untreated control. Epoxiconazole used alone gave the poorest disease control, but did increase the yield. The three partner fungicides all improved disease control and yield; two applications of half-rate epoxiconazole with half-rate azoxystrobin or cyprodinil performed best overall. With the range of pathogen sensitivities found in the present study, a DMI such as epoxiconazole remains a useful component of a control programme for R. secalis, but should be supplemented by a partner fungicide with a different mode of action such as a strobilurin or anilinopyrimidine.

Rhynchosporium secalis causes an economically important foliar disease of barley, rye, and other grasses known as leaf blotch or scald. This species has been difficult to classify due to a paucity of morphological features; the genus Rhynchosporium produces conidia from vegetative hyphae directly, without conidiophores or other structures. Furthermore, no teleomorph has been associated with R. secalis, so essentially nothing is known about its phylogenetic relationships. To identify other fungi that might be related to R. secalis, the 18S ribosomal RNA gene and the internal transcribed spacer (ITS) region (ITS1, 5.8S rRNA gene, and ITS2) were sequenced and compared to those in databases. Among 31 18S sequences downloaded from GenBank, the closest relatives to R. secalis were two species of Graphium (hyphomycetes) and two other accessions that were not identified to genus or species. Therefore, 18S sequences were not useful for elucidating the phylogenetic relationships of R. secalis. However, analyses of 76 ITS sequences revealed very close relationships among R. secalis and species of the discomycete genera Tapesia and Pyrenopeziza, as well as several anamorphic fungi including soybean and Adzuki-bean isolates of Phialophora gregata. These species all clustered together with 100% bootstrap support. On the basis of these results, the teleomorph of R. secalis, if it exists, most likely will be a small apothecium produced directly on dead, infected host tissue. The ITS analysis also indicated that higher-level classifications within the discomycetes need to be revised, and that Tapesia and Pyrenopeziza probably do not belong in the Dermateaceae.

Evolution of resistance to drugs and pesticides poses a serious threat to human health and agricultural production. CYP51 encodes the target site of azole fungicides, widely used clinically and in agriculture. Azole resistance can evolve due to point mutations or overexpression of CYP51, and previous studies have shown that fungicide-resistant alleles have arisen by de novo mutation. Paralogs CYP51A and CYP51B are found in filamentous ascomycetes, but CYP51A has been lost from multiple lineages. Here, we show that in the barley pathogen Rhynchosporium commune, re-emergence of CYP51A constitutes a novel mechanism for the evolution of resistance to azoles. Pyrosequencing analysis of historical barley leaf samples from a unique long-term experiment from 1892 to 2008 indicates that the majority of the R. commune population lacked CYP51A until 1985, after which the frequency of CYP51A rapidly increased. Functional analysis demonstrates that CYP51A retains the same substrate as CYP51B, but with different transcriptional regulation. Phylogenetic analyses show that the origin of CYP51A far predates azole use, and newly sequenced Rhynchosporium genomes show CYP51A persisting in the R. commune lineage rather than being regained by horizontal gene transfer; therefore, CYP51A re-emergence provides an example of adaptation to novel compounds by selection from standing genetic variation.

An outline is given of results for the transfer of new resistances against leaf rust and barley mosaic viruses from Hordeum bulbosum into winter barley. Progenies from backcrosses of barley cultivars with H. bulbosum hybrids were tested both in conventional breeding trials and in additional tests under controlled conditions. Resistance to both pathogens proved to be stable and of good heritability, with differences occurring which depended on the combinations used. Lines with resistance to all leaf rust and mosaic viruses tested, or to either one, were selected. Both resistances segregated independently.

Spring barley cultivars currently grown in Germany are all more or less susceptible to Rhynchosporium secalis (Oudem.) J.J. Davis, but there are obvious differences in the degree of susceptibility under field conditions. Small genotypic differences may be caused by both genetic and environmental effects, respectively. To minimize the influence of environmental variation on disease expression, several inoculation methods were developed in the present study. In two experiments the effectiveness of the inoculation by spraying of single spore isolates was tested in the glasshouse and in the field, respectively. High infection levels were achieved in the glasshouse. Despite the infection of barley in the field, disease expression levels remained low due to unfavourable conditions. Another experiment showed the usefulness of infected straw applied in the autumn only for testing the seedling infection type of spring barley cultivars against R, secalis. Seedling assay scores and field infection levels were closely related (r = 0.796, P < 0.01; r = 0.911, P < 0.001). Therefore, both the spray infection technique in the glasshouse and the inoculation technique using infected straw in the field appear to be suitable to detect genetic differences in resistance/susceptibility of spring barley cultivars against leaf blotch. Zusammenfassung Aktuelle europaische Sommergerstensorten sind mehr Oder weniger anfallig gegen Rhynchosporium secalis(Oudem.) J.J. Davis, aber unter variierenden Freilandbe-dingungen sind doch signifikante Sortenunterschiede feststellbar. Dabei konnen gentoypische Differenzierungen sowohl durch genetische als auch durch umweltbedingte Effekte verursacht sein. In der vorliegenden Studie wurden verschiedene kunstliche Inokulationsmethoden unter verschiedenen Bedingungen erprobt, um den Ein-fluβ der naturlichen Umweltverhaltnisse zu minimieren. In zwei Exprimenten wurde die Effekivitat einer Spruh-inokulation mit Einzelsporensuspensionen im Gewachs-haus und Freiland untersucht. Dabei wurden gerade im Gewachshaus hohe Infektionsraten erzielt, wahrend der Infektionserfolg unter Feldbedingungen aufgrund ungunstiger Bedingungen weitgehend gering blieb. In einem weiteren Versuch zeigte sich die gunstige Wirkung von infiziertem Gerstenstroh bei Ausbringung im Herbst fur die Prufung von Gerstenkeimlingen bzw. Jungpflanzen auf Resistenz gegen R. secalis. Die Keim-lingsreaktion und die Reaktion erwachsener Pflanzen unter ublichen Freilandbedingungen zeigten eine relative enge Korrelation (r = 0.796, P < 0.01; r = 0.911, P < 0.001). Daraus kann gefolgert werden, daβ sowohl eine Spruhinokulation im Gewachshaus als auch eine kunstliche Infektion mit Hilfe von infiziertem Stroh unter Freilandbedingungen dafur geeignet sind genetische Differenzierungen im Hinblick auf Resistenz/Anfalligkeit von Sommergerstensorten gegen Rhynchosporium Blattflecken zu erfassen.

The literature reports that evaluations over a number of growing seasons are required to identify stable disease resistance in rice (Oryza sativa L.). CIAT's Rice Breeding Program aims to develop lines with stable resistance; therefore, the knowledge of how long a germplasm should be assessed before being used in crosses is important. For this research, 69 commercial cultivars grown in Latin America and the Caribbean were evaluated during 11 growing seasons in a 'hot spot' site for the four most important diseases of rice: leaf and panicle blast (caused by Pyricularia grisea Sacc.), leaf scald [caused by Microdochium oryzae (Hashioka & Yokogi) Samuels & I.C. Hallett syn. Gerlachia oryzae (Hashioka & Yokogi) W. Gams syn. Rhynchosporium oryzae (Hashioka & Yokogi)], and grain discoloration (caused by species of Sarocladium, Bipolaris, Alternaria, Gerlachia, Fusarium, Phoma, Curvularia, Trichoconiella, and Pseudomonas). Cultivar mean disease severity (M), its response to increase in disease pressure (b), and the standard deviations from the regression (Sb) were calculated. Eleven evaluation seasons were considered as the most reliable period, in which an ideal set of 13 cultivars was identified based on their disease resistance stability (M, b, and Sb values). To identify the minimum number of seasons required to assess stability of resistance, simulations were made with these 13 cultivars and the 11 seasons and the coincidence in selection and the number of misclassified entries were calculated. The M and b correlation values and the number of misclassified entries suggested that seven consecutive growing seasons (two per 12-mo. period) are necessary to identify germplasm with stable reaction to leaf and panicle blast, leaf scald, and grain discoloration.

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., PLoS ONE, 8 (10), ISSN:1932-6203

The fungicide propiconazole, applied as a foliar spray to swards of perennial ryegrass (Lolium perenne) at four sites in England from 1990 to 1992, reduced the incidence of powdery mildew (Blumeria graminis), Drechslera leaf spot (Drechslera spp.) and Rhynchosporium leaf blotch (Rhynchosporium spp.), increased the number of leaves per tiller and reduced the proportion of dead leaves. Propiconazole increased yield, by 6–7%, at harvests in mid-May, but had no effect at harvests in late June, when the cut herbage was dried to produce hay, although in one hay crop, in vitro organic matter digestibility was increased from 575.6 to 588.5 g kg−1 (P < 0.05). Further research is required to determine the rationale and optimum timing of fungicide application to grassland.

European Journal of Plant Pathology, 129 (4), ISSN:0929-1873, ISSN:1573-8469

Summary Samples from 200–400 randomly selected winter barley crops were taken annually at growth stage 71–73 from 1981 to 1991, with the exception of 1984 and 1985. The number of samples from each region was proportional to the area of barley growth in each region. The percentage of the area of the top two leaves affected by diseases and the severity of stem base diseases were recorded. Mildew (Erysiphe graminis) was the most widespread of the foliar diseases and in three years (1982, 1986 and 1991) was also the most severe. Rhynchosporium (Rhynchosporium secalis), net blotch (Pyrenophora teres) and brown rust (Puc-cinia hordei) were also prevalent in some years. Of the stem base diseases, fusarium was often the most widespread. Eyespot (Pseudocercosporella her-potrichoides) severity varied widely from year to year ranging from 1.2% of stems affected by moderate or severe symptoms in 1982 to 24.1% in 1988. There were regional differences in the severity of mildew, rhynchosporium, brown rust, halo spot (Selenophoma donacis) and eyespot. Cultivar resistance affected disease severity and previous cropping affected eyespot and less frequently mildew, rhynchosporium and net blotch. Eyespot, and to a lesser extent, sharp eyespot, were less severe in late- than in early-sown crops. The percentage of crops treated with a fungicidal spray increased from 72% in 1981 to 95% in 1991. The use of benzimidazole fungicides for the control of eyespot declined in response to the development of resistance, and more recently the use of prochlo-raz also declined. Broad spectrum DMI fungicides were widely used, and the use of morpholines to improve mildew control increased significantly. The proportion of crops grown from seed treated with a non-mercurial fungicidal seed dressing reached a peak of 47% in 1986 but subsequently declined to 22% in 1990 and 1991.

Summary Samples from 200–300 randomly selected spring barley crops were taken annually at growth stage 73–77 (milky ripe) from 1976 to 1980. The number of samples from each region was proportional to the area of barley grown in each region. The percentage of the area of the top two leaves affected by diseases was recorded. Mildew (Erysiphe graminis) was the most widespread and severe disease recorded. Brown rust (Puccinia hordei) and rhynchosporium (Rhyn-chosporium secalis) occurred frequently but at relatively low levels. Yellow rust {Puccinia striiformis) and septoria (Septoria nodorum) were seen on less than 50% of the samples in most years, and halo spot (Selenophoma donacis) and net blotch (Pyrenophora teres) were rarely recorded. There was an association between the severity of rhynchosporium and the number of rain days in May and June. The highest levels of brown rust occurred in the south and east and rhynchosporium was more common in Wales and the south-west than in the east, but there were no differences in the regional distribution of other diseases. Cultivar resistance, sowing date, previous cropping and fungicide usage were all found to be associated with altered disease levels. The proportion of crops treated with a foliar fungicidal spray rose from 26% in 1976 to 47% in 1980. The use of tridemorph declined but that of triadimefon increased reaching 29% of crops treated by 1980. The use of ethirimol as a seed treatment declined from 16% of crops grown from treated seed in 1976 to 7% in 1980. Estimated yield losses between 1976 and 1980 varied between 4% and 9% due to mildew, between 0.3% and 0.8% due to brown rust and between 0.2% and 0.5% due to rhynchosporium.

Laboratory tests on 2000 isolates of Rhynchosporium secalis from throughout the UK over a 4-year period revealed a decline in sensitivity to triadimenol and propiconazole but not to prochloraz. Change occurred throughout the UK irrespective of disease pressure, and was not correlated with fungicide use. Resistant isolates were no less pathogenic than sensitive ones. Selection with triadimenol generated a bimodal population distribution, whereas propiconazole produced a gradual shift of unimodal population towards a less sensitive mean. Some cross-resistance occurred between triadimenol, propiconazole and a third triazole, tebuconazole, although the change in sensitivity to tebuconazole was always less than to the other two triazoles. No cross-resistance was observed to the imidazole demethylation inhibitor (DMI), prochloraz. Field-trial data collected over several years showed that the performance of triadimenol, and to a lesser extent, of propiconazole, had declined. Control of Rhynchosporium with these fungicides could be improved by using mixtures with carbendazim. Tebuconazole, either alone or in mixtures with carbendazim or tridemorph, provided the best disease control, and did not appear to select for lower sensitivity. The findings emphasize that certain DMI fungicides may still be used in strategies where performance of other DMIs has been altered because of resistance.

The incidence and severity of infection by fungal diseases was recorded on youngest fully expanded leaves of perennial ryegrass (Lolium perenne) in May and/or September from 1985 to 1987 at 16 sites in England and Wales. Leaves were collected from swards of a single cultivar, Melle, given the same management at each site. Drechslera spp. were present at all sites, and infection exceeded 10% of leaves at eight sites. Rhynchosporium spp. were present at 15 sites but infection exceeded 10% of leaves at only two sites in southern England. Powdery mildew (Erysiphe graminis) was present at 10 sites and infection exceeded 20% of leaves at four sites. Crown rust (Puccinia coronata) was present at six sites, mainly in central and southern England, and infection exceeded 10% of leaves at two sites. Mildew and rust were present only in September, Drechslera was more frequent in September than May and Rhynchosporium was about equally frequent in May and September. The area of leaf damaged by Rhynchosporium ranged from 5 to 23% overall; the range for the other diseases was 1–3%.

Penetration and colonization of orchardgrass by Rhynchosporium orthosporum and production of conidia by the fungus were investigated by light, fluorescent, and scanning electron microscopy. Conidia...

A total of 1,366 Rhynchosporium secalis isolates causing scald on barley, rye, and wild barley (Hordeum spontaneum) were assayed for restriction fragment length polymorphism loci, DNA fingerprints, and mating type, to characterize global genetic structure. The isolates originated from 31 field populations on five continents. Hierarchical analysis revealed that more than 70% of the total genetic variation within regions was distributed within a barley field. At the global level, only 58% of the total genetic variation was distributed within fields, while 11% was distributed among fields within regions, and 31% was distributed among regions. A significant correlation was found between genetic and geographic distance. These findings suggest that gene flow is common at the local level while it is low between regions on the same continent, and rare between continents. Analyses of multilocus associations, genotype diversity, and mating type frequencies indicate that sexual recombination is occurring in most of the populations. We found the highest allele richness in Scandinavia followed by Switzerland. This suggests that R. secalis may not have originated at the center of origin of barley, the Fertile Crescent, nor in a secondary center of diversity of barley, Ethiopia.