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Genotype diversities and their standard errors (in parenthesis) in Rhynchosporium secalis collections made from different host treatments and sampling times in Tel Hadya in 2004 and 2005, and Lattakia in 2004
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ABSTRACT Competition among eight Rhynchosporium secalis isolates was assessed during parasitic and saprophytic phases of the disease cycle in field experiments conducted at two locations and over two growing seasons. The eight isolates were inoculated onto six barley populations exhibiting varying degrees of resistance. Microsatellite analysis of 2...
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Context 1
... diversity in the pathogen collections across host populations. Although not significant, genotype diversity in pathogen collections from all five host treatments at Tel Hadya decreased from early to late season in 2004 ( Table 4). The fungal collection from Arabi Aswad in 2004 consistently had the lowest genotype diversity, while that from WI2291 had the highest diver- F value = 184.08 ...
Context 2
... between Tel Hadya and Lattakia showed that genotype diversities decreased during 2004 at Tel Hadya while increasing over the season at Lattakia. In 2004, the genotype diversities of the pathogen populations from the mixture and Rihane at Tel Hadya were significantly (P < 0.05) lower than the genotype diversities on the same hosts at Lattakia (Table 4). Temporal and spatial variation in fitness and local adapta- tion of pathogen strains. ...
Citations
... using agricolae library. Briefly, a 0-to-5 scale was used, where 0 = symptom free, 1 = traces or small necrotic flecks, 2 = some chlorosis or necrosis along margins, 3 = necroses but less than 40% affected tissue, 4 = necroses on 40 to 80% of the lamina, and 5 = more than 80% and up to a fully wilted leaf (Abang et al., 2006). ...
... The resilience of fifty-five cultivars against a virulent isolate was assessed according to 0-5 scale (Abang et al., 2006). In accordance with the scores of the assessments, Erginel-90 was immune, seven cultivars ( Avcı-2002, Ocak, Kendal, Hevsel, Yüksel, Şahin-91 and Akhisar-98) showed resistance and twenty-nine cultivars exhibited susceptible reactions (Table 1). ...
... The isolates in the previous study and in this study were obtained from the same province, which may indicate the evolution of the pathogen population. The other studies confirm that the pathogen may adopt rapidly, therefore overcoming the resistance of the plants (Williams, 2003;Abang et al., 2006;Zaffarano et al., 2006)866 isolates recovered from the field experiments showed significant, and sometimes opposite, changes in the frequencies of R. secalis genotypes during the growing season (parasitic phase.) ...
Barley is one of the significant cereal used as hay and malt both in the world and in Turkey. There are several abiotic and biotic factors affecting the production and quality of barley. Of these factors, fungal diseases play a vital role. Especially, barley scald (Rhynchosporium commune), a fungal pathogen, is threating the barley grown areas in terms of the quality and the production. One of the most common methods in controlling of this fungal diseasis to develop resistant barley varieties. The study carried out in the laboratories and greenhouses of Field Crop Central Research Institute, Yenimahalle, Ankara in 2020-2021. Aim of this study was to investigate the reaction of 55 registered barley cultivars against barley scald. The results show that Erginel-90 is immun, as well Avcı-2002, Ocak, Kendal, Hevsel, Yükse, Şahin-91 and Akhisar-98 varieties are resistant. On the other hand, Yesevi-93, Tarm-92, Orza-96, Larende, Bülbül-89, Karatay-94 and Ayrancı are detected as susceptible to this disease.
... Nevertheless, localized regional losses of up to 65% might happen during epidemic years [10]. Additionally, yield losses close to 100% have been reported from regions where barley is grown continuously almost without crop rotation, such as in some regions such as Tunisia, Morocco, Eritrea, and Ethiopia [11,13], Peru, Colombia, Bolivia, Ecuador, Turkey, Syria, Iran [10,12,13]. Cope et al. [15], revised that scald disease can also cause about $7.2 yield loss to barley crops in the UK. ...
... Nevertheless, localized regional losses of up to 65% might happen during epidemic years [10]. Additionally, yield losses close to 100% have been reported from regions where barley is grown continuously almost without crop rotation, such as in some regions such as Tunisia, Morocco, Eritrea, and Ethiopia [11,13], Peru, Colombia, Bolivia, Ecuador, Turkey, Syria, Iran [10,12,13]. Cope et al. [15], revised that scald disease can also cause about $7.2 yield loss to barley crops in the UK. ...
Barley scald is very important in temperate and wet regions worldwide and has become one of the most important foliar diseases. Before the development of recent technologies, several scientists had argued that Rhynchosporium secalis is the causal agent of scald disease. However, the causal agent of this disease was revised and recognized as Rhynchosporium commune. Again recently, Rhynchosporium graminicola was suggested to be replaced as the causal agent of R. commune. The disease outbreak is depending on cool and frequent rainfall. Because of scald disease significance, numerous management practices have been advocated. Then, resistance materials, and mixing of resistant and susceptible cultivars have been used as the best management methods. Several studies have demonstrated that some cultivars and landraces of barley are resistant to scald disease during the seedling and adult growth stages. The first cultivar is “Atlas 46″ which was created from the cultivar “Turk”. From biological method: Bacillus polymyxa, Paenibacillus polymyxa KaI245, and Bacillus subtilis are very effective in treating this disease. Finally, as a last option, different fungicides have been suggested. Pathogenicity testing, seed treatments, tillage, cultivar mixtures, and biological control are all commonly overlooked in developing countries. Cultural practices such as times of fungicide application, appropriate time of sowing to scape disease, and tillage practices which are adopted for other diseases are greatly missed for scald disease. Then, we are intended to assess the various findings available on barley scald biology, taxonomy, and management.
... It is unclear what evolutionary forces would promote the maintenance of high variation for virulence within single, isolated subpopulations, although a similar phenomenon has been observed in fungal pathogen Zymoseptoria tritici (Dutta et al. 2021). One possibility is that diversifying selection acts to favor both highly virulent isolates with increased fitness on healthy hosts as well as less virulent, more saprophytic isolates that are preferentially able to colonize dead tissue, as shown in fungal barley pathogen Rynchosporium secalis (Abang et al. 2006). ...
The development of pepper cultivars with durable resistance to the oomycete Phytophthora capsici has been challenging due to differential interactions between the species that allow certain pathogen isolates to cause disease on otherwise resistant host genotypes. Currently, little is known about the pathogen genes involved in these interactions. To investigate the genetic basis of P. capsici virulence on individual pepper genotypes, we inoculated sixteen pepper accessions – representing commercial varieties, sources of resistance, and host differentials – with 117 isolates of P. capsici, for a total of 1,864 host-pathogen combinations. Analysis of disease outcomes revealed a significant effect of inter-species genotype-by-genotype interactions, although these interactions were quantitative rather than qualitative in scale. Isolates were classified into five pathogen subpopulations, as determined by their genotypes at over 60,000 single-nucleotide polymorphisms (SNPs). While absolute virulence levels on certain pepper accessions significantly differed between subpopulations, a multivariate phenotype reflecting relative virulence levels on certain pepper genotypes compared to others showed the strongest association with pathogen subpopulation. A genome-wide association study (GWAS) identified four pathogen loci significantly associated with virulence, two of which colocalized with putative RXLR effector genes and another with a polygalacturonase gene cluster. All four loci appeared to represent broad-spectrum virulence genes, as significant SNPs demonstrated consistent effects regardless of the host genotype tested. Host genotype-specific virulence variants in P. capsici may be difficult to map via GWAS with all but excessively large sample sizes, perhaps controlled by genes of small effect or by multiple allelic variants that have arisen independently.
... Thus, this permits the compete population to develop and reproduce actively over the parasitic phase (Leach et al., 2001). Several reports have demonstrated that the adaptation of fungal plant pathogens, in terms of parasitic or saprophytic fitness traits, can occur after repeated cycling on the same host (Ahmed et al., 1996;Lehman and Shaner, 1997;Cowger and Mundt, 2002;Akinsanmi et al., 2007;Abang et al., 2006;Wang et al., 2008).The evolution of phytopathogenic organisms when faced with selective pressures in the host may be constrained by fitness costs linked with adaptation to QR (cost of aggressiveness) (Leach et al., 2001). Fusarium head blight (FHB) is an economically principal disease of barley and other small grain cereals (i.e., triticale, rye, oat and wheat) (Parry et al., 1995). ...
... Also, adaptation to quantitative resistance was correlated by an augmentation in aggressiveness, indicating that pathogen populations changeably adapted depending on selective pressures imposed by barley plants with contrasted resistance levels. Such observation has been supported by a study investigating quantitative resistance selection in barley on Rhynchosporium secalis, a scald pathogen (Abang et al., 2006). It has been mainly accepted that highly aggressive FHB isolates may induce more grave symptoms in moderately resistant barley cultivars than do less aggressive isolates; thus, isolate-specific resistance has not been observed (Xu and Nicholson, 2009). ...
Fusarium head blight (FHB) leads to significant quality and yield losses makes the FHB disease an important threat in all barley-growing areas of the world. Till now, available empirical data are limited on the efficiency of quantitative barley resistance expected to reduce in several generations because of the selection of FHB isolates with a high level of quantitative component of pathogenicity, i.e., aggressiveness, because of the difficulty of conducting such studies in the field. To achieve this goal, the evolutionary aggressiveness response were analyzed in four FHB pathogens faced with selective pressure using in vitro serial passage assays on susceptible “S” and moderately resistant “MR” barley. Differences due to the selective effect of a cultivar among non-selected and selected FHB isolates were quantified for traits participating to parasitic (area under disease progress curve ( AUDPC ) and latent period (LP)) fitness. The pathogen populations adapted quickly to the “MR” cultivar than the “S” cultivar. The selective barley impact on the analyzed FHB pathogens seemed to be species-specific. The results showed that selected isolates on the “MR” cultivar presenting a high level of aggressiveness than selected isolates from “S” cultivar, as they had a shorter LP (21.8%) and a higher level of AUDPC (22.1%). These findings provide the first direct evidence that FHB pathogens evolve rapidly to adapt by increasing aggressiveness to barley, indicating a risk of directional selection (i.e., deployment of a resistance gene) and possible erosion, evolution of aggressiveness due to resistance selection pressure over generations can lead to quantitative resistance erosion, of barely resistance, a vital component for the progress of durable control policies for resistant barley cultivars to FHB infection.
... The presence of high levels of phenotypic variability in aggressiveness traits is a key basis for rapid adaptation, and selection for these traits can happen during a shorter number of generations Mundt, 2014). Former experimental researches on fungal plant pathogens have proposed that the erosion of quantitative plant resistance comes with the selection of greater pathogen aggressiveness (Ahmed et al., 1996;Lehman and Shaner, 1997;Cowger and Mundt, 2002;Abang et al., 2006;Wang et al., 2008). Aggressiveness traits directly related to parasitic fitness can be evaluated by assessing multiple quantitative components such as infection efficiency, infectious period, latent period, sporulation rate and lesion size (Pariaud et al., 2009). ...
... Thus, this permits the compete population to grow and reproduce actively during the parasitic phase (Leach et al., 2001). Various researches have provided evidence that the adaptation of fungal plant pathogens, in terms of parasitic or saprophytic fitness traits, can occur after repeated cycling on the same host (Ahmed et al., 1996;Lehman and Shaner, 1997;Cowger and Mundt, 2002;Abang et al., 2006;Akinsanmi et al., 2007;Wang et al., 2008). "Serial passage assays" were designed, accompanied by the inoculation of a host plant with a pathogen population, followed by the inoculation of a novel series of plants with the progeny of the initial pathogen population, repeated during diverse cycles. ...
... To date, the findings that are accessible tend to assist the conclusion that plant pathogen rearing for several generations on resistant hosts select for more aggressive pathogens than do susceptible hosts (Lehman and Shaner, 1997;Cowger and Mundt, 2002;Abang et al., 2006;Delmas et al., 2016). It seems that isolates with higher aggressiveness will increase in frequency due to directional selection on quantitatively resistant cultivars that are cultivated over a large area for several years, eroding the efficacy of the resistance (McDonald and Linde, 2002). ...
... It is unclear what evolutionary forces would promote the maintenance of high variation for virulence within single, isolated subpopulations, although a similar phenomenon has been observed in fungal pathogen Zymoseptoria tritici (Dutta et al. 2021). One possibility is that diversifying selection acts to favor both highly virulent isolates with increased fitness on healthy hosts as well as less virulent, more saprophytic isolates that are preferentially able to colonize dead tissue, as shown in fungal barley pathogen Rynchosporium secalis (Abang et al. 2006). ...
The development of pepper cultivars with durable resistance to the oomycete Phytophthora capsici has been challenging due to differential interactions between the species that allow certain pathogen isolates to cause disease on otherwise resistant host genotypes. Currently, little is known about the pathogen genes that are involved in these interactions. To investigate the genetic basis of P. capsici virulence on individual pepper genotypes, we inoculated sixteen pepper accessions — representing commercial varieties, sources of resistance, and host differentials — with 117 isolates of P. capsici , for a total of 1,864 host-pathogen combinations. Analysis of disease outcomes revealed a significant effect of inter-species genotype-by-genotype interactions, although these interactions were quantitative rather than qualitative in scale. Isolates were classified into five pathogen subpopulations, as determined by their genotypes at over 60,000 single-nucleotide polymorphisms (SNPs). While absolute virulence levels on certain pepper accessions significantly differed between subpopulations, a multivariate phenotype reflecting relative virulence levels on certain pepper genotypes compared to others showed the strongest association with pathogen subpopulation. A genome-wide association study (GWAS) identified four pathogen loci significantly associated with virulence, two of which colocalized with putative RXLR effector genes and another with a polygalacturonase gene cluster. All four loci appeared to represent broad-spectrum virulence genes, as significant SNPs demonstrated consistent effects regardless of the host genotype tested. Host genotype-specific virulence variants in P. capsici may be difficult to map via GWAS, perhaps controlled by many genes of small effect or by multiple alleles that have arisen independently at the same loci.
... So far, 148 quantitative trait loci (QTL) for scald resistance have been reported in barley (reviewed in Zhang et al. 2020) including the following major resistance genes (R-genes): Rrs14 on chromosome 1H, Rrs17 on 2H, Rrs1 and Rrs4 on 3H, Rrs16 on 4H, Rrs13 and Rrs18 on 6H, Rrs2, Rrs 12, Rrs15, on 7H. R. commune is a genetically highly diverse pathogen (Abang et al. 2006;McDonald 2015), which emphasizes the importance of using partial resistance over single R-genes and also the need to find new resistance mechanisms to replace the ones that are already overcome by pathogen evolution. For example, the effector protein NIP1, which is the product of the R. commune avirulence gene Avr-Rrs1 (Rohe et al. 1995), is recognized by cultivars carrying the major R-gene Rrs1. ...
... R-genes trigger plant defence responses by directly or indirectly recognizing the products of avirulence genes expressed by the pathogen during infection. However, due to the simple genetic architecture of this interaction, major gene-mediated resistance can be broken down after only a short period of commercial cultivation (Abang et al. 2006), unless the avirulence gene product is essential to the pathogen. Partial resistance is shown to reduce scald severity (Williams and Owen 1975;Kari and Griffiths 1993;Looseley et al. 2012). ...
Genome-Wide Association Studies (GWAS) of four Multi-parent Advanced Generation Inter-Cross (MAGIC) populations identified nine regions on chromosomes 1H, 3H, 4H, 5H, 6H and 7H associated with resistance against barley scald disease. Three of these regions are putatively novel resistance Quantitative Trait Loci (QTL). Barley scald is caused by Rhynchos-porium commune, one of the most important barley leaf diseases that are prevalent in most barley-growing regions. Up to 40% yield losses can occur in susceptible barley cultivars. Four MAGIC populations were generated in a Nordic Public-Private Pre-breeding of spring barley project (PPP Barley) to introduce resistance to several important diseases. Here, these MAGIC populations consisting of six to eight founders each were tested for scald resistance in field trials in Finland and Iceland. Eight different model covariate combinations were compared for GWAS studies, and the models that deviated the least from the expected p-values were selected. For all QTL, candidate genes were identified that are predicted to be involved in pathogen defence. The MAGIC progenies contained new haplotypes of significant SNP-markers with high resistance levels. The lines with successfully pyramided resistance against scald and mildew and the significant markers are now distributed among Nordic plant breeders and will benefit development of disease-resistant cultivars.
... These various life-history tactics are projected to produce various epidemiological patterns and impose markedly varied selection regimes on hosts and their diseases[51]. Indeed, as the barley scald pathogen Rhynchosporium secalis demonstrates, selection pressures may be considerably different between the parasitic and saprophytic stages of the life cycle[72]. Examples of this kind of hostpathogen interaction include assault by several leaf diseases (e.g.,Meadowsweet [Filipendula ulmaria] was attacked by Triphragmium [biotrophic rust] and Ramularia [necrotrophic leaf blight]) or pathogens targeting many organs of a plant (e.g., Populus spp. ...
The simultaneous genetic change in interacting species as a result of mutually imposed natural selection is known as co-evolution. Many biologists believe that the process of co-evolution between plants and the biota that surrounds them, which includes mammals, viruses, fungus, bacteria, insects, and nematodes, is responsible for most of the earth’s biological variety. While most of the debate around plant co-evolution focuses on one host–one pathogen, two or more hosts–one pathogen, and one host–two contrasting co-occurring pathogens single plant–pathogen interactions, a wide range of many other micro-and macroevolutionary processes occur concurrently in a single plant, posing the issue of whether or not we should even discuss it. In this review, we have discussed the framework of co-evolution theory, as well as the complexities of investigating co-evolution in natural conditions.
... Scald attacks barley under very different agro-ecological conditions in Tunisia, from the low rainfall zone of central Tunisia to the high rainfall zone of northwestern Tunisia. The physical environment plays an important role in shaping the genetic structure of local R. secalis populations [20]. Dinoor and Eshed [21] suggested that under adverse, variable climatic conditions, pathogen populations need to maintain higher aggressiveness in order to survive and high genetic diversity is required for adaptability. ...
... Understanding the consequences of selection by host resistance on pathogen population structure provides useful insights into the dynamics of host-parasite co-evolution processes and is crucial for effective disease management through resistant cultivars [20,22,23]. Host selection can have a profound impact on the genetic structure of pathogen populations, especially in pathosystems characterized by the rapid breakdown of race-specific resistance. ...
... However, the cultivar continues to be grown over large areas and currently represents a considerable percentage of the acreage grown to barley in the country. In Syria, Abang et al. [20] found that the selection coefficients of five R. secalis genotypes on Rihane were low relative to those on the moderately resistant cultivar Arabi Aswad, suggesting that Rihane exerts weak selection pressure on R. secalis populations. In this study, we sought to find out if the breakdown of scald resistance in Rihane was accompanied by the selection and eventual predominance of one or a few pathotypes/genotypes that overcame the resistance of this cultivar following its release over 20 years ago. ...
... Differential set for barley scald disease, previously used by Abang et al. (2006), was selected in this experiment. This differential set contained 17 barley scald differential cultivars were obtained from the International Center for Agricultural Research in the Dry Areas (ICARDA), The United States Department of Agriculture (USDA), and Dr. T. Fukuyama (Niigata University, Japan). ...
... In another research carried out in Tunisia, Astrix cultivar was determined as the most resistant cultivar against 75 pathotypes of R. secalis (Bouajila et al. 2010). In a study performed by Abang et al. (2006), 8 isolates tested using barley scald differential cultivars, Armelle, Astrix and Atlas 46 cultivars were found as the most resistant cultivars against all isolates, and Digger cultivar was the most susceptible cultivar to all isolates. In their study, Igri, La Mesita, Jet, and Forrajera cultivars showed susceptible reactions to 6 isolates (76% of isolates) of R. secalis. ...
... Abyssinia cultivar was found as susceptible to 2 isolates and resistant to the 6 isolates. In contrast to Abang et al. (2006) study, Arabi et al. (2008) tested 63 isolates of R. secalis on Igri and 5 other cultivars and reported that Igri which carry BRR4 resistance gene showed resistant reaction to the majority of 46 isolates. Moreover, in Syria, Arabi et al. (2009) assessed 115 isolates of scald against 10 barley differential genotypes. ...
Barley (Hordeum vulgare L.) is one of the important cereal crops grown in the vast area of the world and Turkey. This crop is the second most important cereal in Turkey grown in 2.611.940 hectares of land, and 7.000.000 tonnes of yield was produced (TUİK 2018). Barley scald caused by Rhynchosporium commune Zaffarano, McDonald, and Linde (formerly Rhynchosporium secalis (Oudem.) J.J. Davis) (Zaffarano et al. 2011) is one of the important barley diseases in Turkey (Karakaya et al. 2014). Yield losses of 10%-70% due to this pathogen have been reported (Aktaş 1984, Sheikh Jabbari 2008, Shipton et al. 1974, Zhang et al. 1992). Barley scald is controlled using chemical, agronomical, and genetic resistance measures. Introducing new sources of resistance to scald is accomplished by screening barley genotypes as well as determining the degree of pathogenic variation in R. commune populations. This method may omit the control of this fungus by chemical measures and help to implement environmentally friendly ways of disease control. Knowing pathogenic variability and obtaining barley genotypes resistant to scald can lead to the prevention of disease losses. In this study, surveys were conducted during 2012, 2013, and 2014 in different regions of Turkey, and pathotypes of R. commune in some barley growing areas of Turkey were determined.
