Home • Blumeria graminis f.sp. hordei DH14
Please note that this organism is for archival use only. Please see the current Blumeria graminis f. sp. hordei DH14 site for the latest data and information.
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Figure 1. A confocal image of B. graminis hyphae stained with Alexa 488-wheat germ agglutinin (5). On the surface (septate) hyphae, small secondary appressoria develop: these produce a penetration peg and secondary haustoria. In this image two young haustoria can be seen: the finger-like projections are beginning to form, but have not yet fully extended. Picture by Pietro D. Spanu
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Figure 2. A colony of the barley powdery mildew fungus (Blumeria graminis f. sp. hordei) growing on the leaf surface. The network of hyphae expanding over the leaf surface is visible in the foreground. The erect conidiophores generate masses of airborne conidia visible to the naked eye as a dry powdery mass that is easily dispersed by air currents. Picture by Pietro D. Spanu

The genome sequence and gene predictions of Blumeria graminis were not determined by the JGI, but were downloaded from ENSEMBL and have been published (Pietro D. Spanu et al., 2010). Please note that this copy of the genome is not maintained by the author and is therefore not automatically updated.

The genome of Blumeria graminis f. sp. hordei strain DH14 was sequenced by BBSRC-INRA funded project and annotated manually by a community effort involving researchers in many institutions world-wide (1).

B. graminis causes powdery mildews in grasses, including the common cereals wheat and barley. Host specificity of the “formae specialis” is high: for example f. sp. hordei is capable of infecting barley but not wheat, whist the f. sp. tritici grows only on wheat. Like all powdery mildew fungi, B. graminis is an obligate biotroph: it requires a living host to grow and reproduce. No significant development has been ever observed in axenic culture.  On a host, the mildew fungi conidium germinates to produce a hypha that differentiates an appressorium and a peg that penetrates directly into the epidermal cell. Once inside the cell, the hypha develops a multidigitate haustorium, surrounded by a matrix and a membrane continuous with the host plasma membrane. The haustorium takes up nutrients from the host and is believed to deliver effectors to target the plant’s metabolism and immune system. The haustoria effectively feed the rest of the colony which expands on the surface of the plant, first as a network of branched hyphae (which produce further, secondary haustoria (Fig. 1) and then develops conidiophores which grow perpendicular to the leaf surface and generate masses of conidiophores that are visible as a white powdery mass (hence the name of the disease (Fig.2). The conidia are dispersed by air currents.

The genome of B. graminis f. sp. hordei is estimated to be larger than 130Mb and, like all the other genomes of powdery mildew fungi, is extremely rich in repetitive elements derived mostly from retrotransposons. The wealth of repetitive elements has thus far prevented a full assembly of the contigs (N50 ~ 18kbp). The annotation identified 6,470 genes, which is notably fewer than related non-biotrophic ascomycetes. The low gene count is due to extensive reduction in the size of gene families (few paralogs), and the loss of genes encoding enzymes on specific metabolic pathways, transporters and carbohydrate active enzymes (CAZy). Some of these losses are convergent with losses observed in other unrelated obligate biotrophic pathogens of plants such as the rusts (basidiomycetes) and the downy mildews (oomycetes).  The only protein coding genes that have bucked the gene loss trend are those of candidate secreted effector proteins, which account for over 7% of the overall gene coding capacity(2). The genomes of related B. graminis (other strains (3) and the wheat pathogen (4)) have also been published.

A website dedicated to the release of data on the genomics of B. graminis can be accessed at: http://www.blugen.org/

Genome Reference(s)



  1. Spanu PD et al. Genome expansion and gene loss in powdery mildew fungi reveal tradeoffs in extreme parasitism. Science. 2010 Dec 10;330(6010):1543-6. doi: 10.1126/science.1194573. PubMed PMID: 21148392.
  2. Pedersen C, Ver Loren van Themaat E, McGuffin LJ, Abbott JC, Burgis TA, Barton G, Bindschedler LV, Lu X, Maekawa T, Wessling R, Cramer R, Thordal-Christensen H, Panstruga R, Spanu PD. Structure and evolution of barley powdery mildew effector candidates. BMC Genomics. 2012 Dec 11;13:694. doi: 10.1186/1471-2164-13-694. PubMed PMID: 23231440; PubMed Central PMCID: PMC3582587.
  3. Hacquard S, Kracher B, Maekawa T, Vernaldi S, Schulze-Lefert P, Ver Loren van Themaat E. Mosaic genome structure of the barley powdery mildew pathogen and conservation of transcriptional programs in divergent hosts. Proc Natl Acad Sci U S A. 2013 Jun 11;110(24):E2219-28. doi: 10.1073/pnas.1306807110. Epub 2013 May 21. PubMed PMID: 23696672; PubMed Central PMCID: PMC3683789.
  4. Wicker T, Oberhaensli S, Parlange F, Buchmann JP, Shatalina M, Roffler S, Ben-David R, Doležel J, Šimková H, Schulze-Lefert P, Spanu PD, Bruggmann R, Amselem J, Quesneville H, Ver Loren van Themaat E, Paape T, Shimizu KK, Keller B. The wheat powdery mildew genome shows the unique evolution of an obligate biotroph. Nat Genet. 2013 Sep;45(9):1092-6. doi: 10.1038/ng.2704. Epub 2013 Jul 14. PubMed PMID: 23852167.
  5. Pliego C, Nowara D, Bonciani G, Gheorghe DM, Xu R, Surana P, Whigham E, Nettleton D, Bogdanove AJ, Wise RP, Schweizer P, Bindschedler LV, Spanu PD. Host-induced gene silencing in barley powdery mildew reveals a class of ribonuclease-like effectors. Mol Plant Microbe Interact. 2013 Jun;26(6):633-42. doi: 10.1094/MPMI-01-13-0005-R. PubMed PMID: 23441578.