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Key message: Gene expression at the RBgh2 locus indicates involvement in cAMP/G-protein-coupled signalling and innate immunity in barley powdery mildew adult plant resistance. Barley powdery mildew is a globally significant disease, responsible for reduced grain yield and quality. A major effect adult plant resistance gene, RBgh2, was previously found in a landrace from Azerbaijan. The atypical phenotype suggested different underlying genetic factors compared to conventional resistance genes and to investigate this, genome-wide gene expression was compared between sets of heterogeneous doubled haploids. RBgh2 resistance is recessive and induces both temporary genome-wide gene expression changes during powdery mildew infection together with constitutive changes, principally at the RBgh2 locus. Defence-related genes significantly induced included homologues of genes associated with innate immunity and pathogen recognition. Intriguingly, RBgh2 resistance does not appear to be dependent on salicylic acid signalling, a key pathway in plant resistance to biotrophs. Constitutive co-expression of resistance gene homologues was evident at the 7HS RBgh2 locus, while no expression was evident for a 6-transmembrane gene, predicted in silico to contain both G-protein- and calmodulin-binding domains. The gene was disrupted at the 5′ end, and G-protein-binding activity was suppressed. RBgh2 appears to operate through a unique mechanism that co-opts elements of innate immunity. [ABSTRACT FROM AUTHOR]

The fungus Blumeria graminis f. sp. tritici causes wheat powdery mildew disease. Here, we study its spread and evolution by analyzing a global sample of 172 mildew genomes. Our analyses show that B.g. tritici emerged in the Fertile Crescent during wheat domestication. After it spread throughout Eurasia, colonization brought it to America, where it hybridized with unknown grass mildew species. Recent trade brought USA strains to Japan, and European strains to China. In both places, they hybridized with local ancestral strains. Thus, although mildew spreads by wind regionally, our results indicate that humans drove its global spread throughout history and that mildew rapidly evolved through hybridization. The fungus Blumeria graminis f. sp. tritici causes wheat powdery mildew disease. Here, Sotiropoulos et al. analyze a global sample of 172 mildew genomes, providing evidence that humans drove global spread of the pathogen throughout history and that mildew rapidly evolved through hybridization with local fungal strains. [ABSTRACT FROM AUTHOR]

The net form net blotch (NFNB) is a significant disease of barley. Its causal agent, Pyrenophora teres f. teres (PTT), has an important economic impact on yield and grain quality globally. However, the molecular interaction between PTT and barley is not fully understood. The plant–pathogen encounter comprises the secretion of diverse molecules involved in plant defence, including pathogenicity-related proteins, and fungal attack, such as proteinaceous toxins called effectors. The forefront of the molecular crosstalk between plant and fungus is the space between plant cells or apoplast. To explore the suitability of studying apoplastic proteins to assist understanding the host–pathogen interaction, a mass spectrometry-based proteomics technique was used to profile apoplastic protein differences in control and NFNB-infected leaves in a susceptible cultivar. The analysis revealed 1130 barley proteins, of which 140 were found to be significantly differentially expressed. This paper presents an overview of the major protein changes induced in the barley apoplast and discusses the involvement of individual proteins in defence and disease development. Our results suggest that the fungus may be hijacking defence signalling pathways. This investigation provides the first in vivo proteomics data for a NFNB–barley interaction, setting a background for further studies. [ABSTRACT FROM AUTHOR]

Knowledge of genetic diversity in A. rabiei provides different levels of information that are important in the management of crop germplasm resources. Gene flow on a regional level indicates a significant potential risk for the regional spread of novel alleles that might contribute to fungicide resistance or the breakdown of resistance genes. Simple sequence repeat (SSR) and mating type (MAT) markers were used to determine the genetic structure, and estimate genetic diversity and the prevalence of mating types in 103 Ascochyta rabiei isolates from seven counties in the Ilam and Kermanshah provinces of western Iran (Ilam, Aseman abad, Holaylan, Chardavol, Dareh shahr, Gilangharb, and Sarpul). A set of 3 microsatellite primer pairs revealed a total of 75 alleles; the number of alleles varied from 15 to 34 for each marker. A high level of genetic variability was observed among A. rabiei isolates in the region. Genetic diversity was high (He = 0.788) within populations with corresponding high average gene flow and low genetic distances between populations. The smallest genetic distance was observed between isolates from Ilam and Chardavol. Both mating types were present in all populations, with the majority of the isolates belonging to Mat1-1 (64%), but within populations the proportions of each mating type were not significantly different from 50%. Results from this study will be useful in breeding for Ascochyta blight-resistant cultivars and developing necessary control measures. [ABSTRACT FROM AUTHOR]

The first predominantly gene-based genetic linkage map of lentil ( Lens culinaris ssp. culinaris) was constructed using an F5 population developed from a cross between the cultivars Digger (ILL5722) and Northfield (ILL5588) using 79 intron-targeted amplified polymorphic (ITAP) and 18 genomic simple sequence repeat (SSR) markers. Linkage analysis revealed seven linkage groups (LGs) comprised of 5–25 markers that varied in length from 80.2 to 274.6 cM. The genome map spanned a total length of 928.4 cM. Clear evidence of a simple and direct macrosyntenic relationship between lentil and Medicago truncatula was observed. Sixty-six out of the 71 gene-based markers, which were previously assigned to M. truncatula genetic and physical maps, were found in regions syntenic between the Lens c. ssp. culinaris and M. truncatula genomes. However, there was evidence of moderate chromosomal rearrangements which may account for the difference in chromosome numbers between these two legume species. Eighteen common SSR markers were used to connect the current map with the most comprehensive and recent map that exists for lentil, providing the syntenic context of four important domestication traits. The composite map presented, anchored with orthologous markers mapped in M. truncatula, provides a strong foundation for the future use of genomic and genetic information in lentil genetic analysis and breeding. [ABSTRACT FROM AUTHOR]

We report the first gene-based linkage map of Lupinus angustifolius (narrow-leafed lupin) and its comparison to the partially sequenced genome of Medicago truncatula. The map comprises 382 loci in 20 major linkage groups, two triplets, three pairs and 11 unlinked loci and is 1,846 cM in length. The map was generated from the segregation of 163 RFLP markers, 135 gene-based PCR markers, 75 AFLP and 4 AFLP-derived SCAR markers in a mapping population of 93 recombinant inbred lines, derived from a cross between domesticated and wild-type parents. This enabled the mapping of five major genes controlling key domestication traits in L. angustifolius. Using marker sequence data, the L. angustifolius genetic map was compared to the partially completed M. truncatula genome sequence. We found evidence of conserved synteny in some regions of the genome despite the wide evolutionary distance between these legume species. We also found new evidence of widespread duplication within the L. angustifolius genome. [ABSTRACT FROM AUTHOR]