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Barley net form net blotch (NFNB) is a destructive foliar disease caused by Pyrenophora teres f. teres. Barley line CIho5791, which harbors the broadly effective chromosome 6H resistance gene Rpt5, displays dominant resistance to P. teres f. teres. To genetically characterize P. teres f. teres avirulence/virulence on the barley line CIho5791, we generated a P. teres f. teres mapping population using a cross between the Moroccan CIho5791-virulent isolate MorSM40-3 and the avirulent reference isolate 0-1. Full genome sequences were generated for 103 progenies. Saturated chromosome-level genetic maps were generated, and quantitative trait locus (QTL) mapping identified two major QTL associated with P. teres f. teres avirulence/virulence on CIho5791. The most significant QTL mapped to chromosome (Ch) 1, where the virulent allele was contributed by MorSM40-3. A second QTL mapped to Ch8; however, this virulent allele was contributed by the avirulent parent 0-1. The Ch1 and Ch8 loci accounted for 27 and 15% of the disease variation, respectively, and the avirulent allele at the Ch1 locus was epistatic over the virulent allele at the Ch8 locus. As a validation, we used a natural P. teres f. teres population in a genome-wide association study that identified the same Ch1 and Ch8 loci. We then generated a new reference quality genome assembly of parental isolate MorSM40-3 with annotation supported by deep transcriptome sequencing of infection time points. The annotation identified candidate genes predicted to encode small, secreted proteins, one or more of which are likely responsible for overcoming the CIho5791 resistance. [Figure: see text] The author(s) have dedicated the work to the public domain under the Creative Commons CC0 “No Rights Reserved” license by waiving all of his or her rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law, 2024.

Pyrenophora teres f. teres (Ptt), the causal agent of net form net blotch (NFNB) disease, is an important and widespread pathogen of barley. This study aimed to quantify and characterize the virulence of Ptt isolates collected from experimental fields of barley in Hungary. Infection responses across 20 barley differentials were obtained from seedling assays of 34 Ptt isolates collected from three Hungarian breeding stations between 2008 and 2018. Twenty-eight Ptt pathotypes were identified. Correspondence analysis followed by hierarchical clustering on the principal components and host-by-pathogen GGE biplots suggested a continuous range of virulence and an absence of specific isolate × barley differential interactions. The isolates were classified into four isolate groups (IG) using agglomerative hierarchical clustering. One IG could be distinguished from other IGs based on avirulence/virulence on one to five barley differentials. Several barley differentials expressed strong resistance against multiple Ptt isolates and may be useful in the development of NFNB-resistant barley cultivars in Hungary. Our results emphasize that the previously developed international barley differential set needs to be improved and adapted to the Hungarian Ptt population. This is the first report on the pathogenic variations of Ptt in Hungary. [ABSTRACT FROM AUTHOR]

Net form net blotch (NFNB), caused by Pyrenophora teres f. teres, is an important barley disease. The centromeric region of barley chromosome 6H has often been associated with resistance or susceptibility to NFNB, including the broadly effective dominant resistance gene Rpt5 derived from barley line CIho 5791. We characterized a population of Moroccan P. teres f. teres isolates that had overcome Rpt5 resistance and identified quantitative trait loci (QTL) that were effective against these isolates. Eight Moroccan P. teres f. teres isolates were phenotyped on barley lines CIho 5791 and Tifang. Six isolates were virulent on CIho 5791, and two were avirulent. A CIho 5791 x Tifang recombinant inbred line (RIL) population was phenotyped with all eight isolates and confirmed the defeat of the 6H resistance locus formerly mapped as Rpt5 in barley line CI9819. A major QTL on chromosome 3H with the resistance allele derived from Tifang, as well as minor QTL, was identified and provided resistance against these isolates. F2 segregation ratios supported dominant inheritance for both the 3H and 6H resistance. Furthermore, inoculation of progeny isolates derived from a cross of P. teres f. teres isolates 0-1 (virulent on Tifang/avirulent on CIho 5791) and MorSM 40-3 (avirulent on Tifang/virulent on CIho 5791) onto the RIL and F2 populations determined that recombination between isolates can generate novel genotypes that overcome both resistance genes. Markers linked to the QTL identified in this study can be used to incorporate both resistance loci into elite barley cultivars for durable resistance. [ABSTRACT FROM AUTHOR]

Net formnet blotch disease, caused by Pyrenophora teres f. teres, results in significant yield losses to barley industries. Up-to-date knowledge of the genetic diversity and structure of pathogen populations is critical for elucidating the disease epidemiology and unraveling pathogen survival and dispersal mechanisms. Thus, this study investigated long-distance dispersal and adaptation by analyzing the genetic structure of 250 P. teres f. teres isolates collected from Australia, Canada, Hungary, and Republic of South Africa (RSA), and historical isolates from Canada, Denmark, Japan, and Sweden. The population genetic structure detected by discriminant analysis of principal components, with the use of 5,890 Diversity Arrays Technology markers, revealed the presence of four clusters. Two of these contained isolates from all regions, and all isolates from RSA were grouped in these two. Australia and Hungary showed three clusters each. One of the Australian clusters contained only Australian isolates. One of the Hungarian clusters contained only Hungarian isolates and one Danish isolate. STRUCTURE analysis indicated that some isolates from Australia and Hungary shared recent ancestry with RSA, Canada, and historical isolates and were thus admixed. Subdivisions of the neighbor joining network indicated that isolates from distinct countries were closely related, suggesting that multiple introduction events conferred genetic heterogeneity in these countries. Through a neighbor joining analysis and amplification with form-specific DNA markers, we detected two hybrid isolates, CBS 281.31 from Japan and H-919 from Hungary, collected in 1931 and 2018, respectively. These results provide a foundation for exploring improved management of disease incursions and pathogen control through strategic deployment of resistance. [ABSTRACT FROM AUTHOR]

Genetic resistance to net form of net blotch in the international barley differential Canadian Lake Shore (CLS) was characterized and mapped. A doubled haploid (DH) population generated from a cross between CLS and susceptible cultivar Harrington was evaluated at the seedling stage using eight diverse Pyrenophora teres f. teres (Ptt) isolates and at the adult stage in the field using natural inoculum. To effectively map the CLS resistance, comparative marker frequency analysis (MFA) was performed using 8,762 polymorphic DArT-seq markers, where ‘resistant’ and ‘susceptible’ groups each comprised 40 DH lines displaying the most extreme phenotypes. Five DArTseq markers were consistently detected in eight disease assays, which was designated qPttCLS and deemed to harbor the locus underpinning CLS resistance. Four of these markers were present onto the barley DArTseq physical map and spans a region between 398203862 and 435526243 bp which were found to consist several genes involved in important plant functions such as disease response and signaling pathways. While MFA only detected the 3H region, genetic analyses based on segregation patterns were inconsistent, suggesting complex inheritance or variation in phenotypic expression of qPttCLS, particularly in the field. This study represents progress toward connecting Ptt pathotype surveys with the corresponding resistance genes in barley differentials. The markers associated with qPttCLS are useful for marker-assisted selection in breeding programs.

Genetic resistance to net form of net blotch in the international barley differential Canadian Lake Shore (CLS) was characterized and mapped. A doubled haploid (DH) population generated from a cross between CLS and susceptible cultivar Harrington was evaluated at the seedling stage using eight diverse Pyrenophora teres f. teres (Ptt) isolates and at the adult stage in the field using natural inoculum. To effectively map the CLS resistance, comparative marker frequency analysis (MFA) was performed using 8,762 polymorphic DArT-seq markers, where 'resistant' and 'susceptible' groups each comprised 40 DH lines displaying the most extreme phenotypes. Five DArTseq markers were consistently detected in eight disease assays, which was designated qPttCLS and deemed to harbor the locus underpinning CLS resistance. Four of these markers were present onto the barley DArTseq physical map and spans a region between 398203862 and 435526243 bp which were found to consist several genes involved in important plant functions such as disease response and signaling pathways. While MFA only detected the 3H region, genetic analyses based on segregation patterns were inconsistent, suggesting complex inheritance or variation in phenotypic expression of qPttCLS , particularly in the field. This study represents progress toward connecting Ptt pathotype surveys with the corresponding resistance genes in barley differentials. The markers associated with qPttCLS are useful for marker-assisted selection in breeding programs. [ABSTRACT FROM AUTHOR]

Net form net blotch (NFNB), caused by Pyrenophora teres f. teres Drechs., is prevalent in barley-growing regions worldwide. A population of 132 recombinant inbred lines (RILs) developed from a cross of the barley varieties ‘Falcon’ and ‘Azhul’ were used to evaluate resistance to NFNB due to their differential reactions to isolates of P. teres f. teres from Australia, Canada, Japan, and the USA. Falcon is a six-rowed, hulless feed barley harboring resistance to NFNB, while Azhul is a six-rowed, hulless food barley with high levels of susceptibility to many P. teres f. teres isolates. Seedling disease resistance data were collected on seedlings of parents, RILs, and checks in a growth chamber. The population was genotyped using Illumina’s GoldenGate assay, and quantitative trait loci (QTL) were detected on chromosomes 2H, 3H, 4H, and 6H. We identified a single genetic region on barley chromosome 4H that provided varying levels of resistance to all P. teres f. teres isolates evaluated. [ABSTRACT FROM AUTHOR]

Barley net form net blotch ( NFNB), caused by the necrotrophic fungus Pyrenophora teres f. teres, is a destructive foliar disease in barley-growing regions worldwide. Little is known about the genetic and molecular basis of this pathosystem. Here, we identified a small secreted proteinaceous necrotrophic effector ( NE), designated PttNE1, from intercellular wash fluids of the susceptible barley line Hector after inoculation with P. teres f. teres isolate 0-1. Using a barley recombinant inbred line (RIL) population developed from a cross between the sensitive/susceptible line Hector and the insensitive/resistant line NDB 112 ( HN population), sensitivity to PttNE1, which we have named SPN1, mapped to a common resistance/susceptibility region on barley chromosome 6H. PttNE1- SPN1 interaction accounted for 31% of the disease variation when the HN population was inoculated with the 0-1 isolate. Strong accumulation of hydrogen peroxide and increased levels of electrolyte leakage were associated with the susceptible reaction, but not the resistant reaction. In addition, the HN RIL population was evaluated for its reactions to 10 geographically diverse P. teres f. teres isolates. Quantitative trait locus ( QTL) mapping led to the identification of at least 10 genomic regions associated with disease, with chromosomes 3H and 6H harbouring major QTLs for resistance/susceptibility. SPN1 was associated with all the 6H QTLs, except one. Collectively, this information indicates that the barley- P. teres f. teres pathosystem follows, at least partially, an NE-triggered susceptibility ( NETS) model that has been described in other necrotrophic fungal disease systems, especially in the Dothideomycete class of fungi. [ABSTRACT FROM AUTHOR]