Blumeria graminis

Blumeria graminis
Blumeria graminis on Elymus repens in Sweden
Scientific classification
Kingdom:	Fungi
Division:	Ascomycota
Class:	Leotiomycetes
Order:	Helotiales
Family:	Erysiphaceae
Genus:	Blumeria
Species:	B. graminis
Binomial name
Blumeria graminis (DC.) Speer, 1975
Synonyms
List Erysiphe graminisDC., 1815 Alphitomorpha communis var. graminearumWallr., 1819 Erysibe communis var. graminumLink, 1824 Acrosporium monilioidesNees, 1817 Oidium monilioides(Nees) Link, 1824 Oospora moniliaformeWallr., 1833 Oospora moniliformisWallr., 1833 Torula papillataBonord., 1861 Oidium papillatum(Bonord.) Sacc. & Voglino, 1886 Torula rubellaBonord., 1860 Oidium rubellum(Bonord.) Sacc. & Voglino, 1886 Monilia hyalinaFr., 1815 Acrosporium hyalinum(Fr.) Sumst., 1913 Oidium triticiLib., 1837 Torula tritici(Lib.) Corda, 1842

Blumeria graminis is a species of powdery mildew in the family Erysiphaceae. It is found around the world where it infects a variety of hosts in the family Poaceae (grasses). It was formerly considered to be the only species of powdery mildew infecting grasses, however there are now at least seven other species in the genus Blumeria . ^[1]

Description

The fungus forms thick white mycelial growth on the leaves of its hosts. With time, the mycelium often turns to tan brown. When present, the chasmothecia are often densely packed. This species reportedly thrives in cool, humid climates and proliferates in cloudy weather conditions. ^[2] As with most Erysiphaceae, Blumeria graminis is fairly host-specific, although it still has a large host range compared to many members of the family. Blumeria graminis can be found infecting Aegilops , Brachypodium , Dasypyrum , Elymus (including Hystrix ), Hordeum , Milium , Phleum , Secale , and Triticum . However, many of these genera more commonly host other species of Blumeria (such as Hordeum with Blumeria hordei ). ^[1] Blumeria graminis can be found on all continents bar Antarctica and in any habitats where its host species can be found. All Erysiphaceae are obligate biotrophs which require a living host to survive, and Blumeria graminis is no exception.

Taxonomy

Blumeria graminis was first described by de Candolle in 1815 with the basionym Erysiphe graminis. ^[3] The former anamorph of this species was Oidium monilinoides. The genus Blumeria was apparently erected to accommodate this species due to its differences with Erysiphe by Golovin in 1958, however this was illegitimately created as it came with no Latin description. In 1975, Speer correctly redescribed the genus and coined the new combination Blumeria graminis. The variation in this species had been long observed, and many formae and formae speciales were created throughout the twentieth century. ^[4] In 2021, Blumeria graminis was split up into multiple different species with varying levels of host specificity. ^[1] The generic name Blumeria is in honour of Samuel Blumer, a Swiss botanist and mycologist whose observations originally indicated the powdery mildews on grasses differed from others in the genus Erysiphe.

Pathology

Blumeria graminis in its former, broadly defined, state has been used many times for studies on the evolutionary relationships between hosts and pathogens. Sequencing of the genome of the (then) B. graminis. f. sp. tritici, allowed inference of important aspects of its evolution. The ability to infect tetraploid as well as domesticated hexaploid wheat, was seen to be the result of mildew genomes being mosaics of ancient haplogroups that existed before wheat domestication. ^[5] The species has even been used to investigate the relationship between two different pathogens on the same host. One study found that the number, size, and reproductive capacity of colonies of Blumeria graminis was reduced by the presence of Zymoseptoria tritici . ^[6]

Due to its prevalence globally and its host specificity to a vital crop species, management of Blumeria graminis has been a high priority for millennia of wheat producers. In the modern day, the most common management technique is the application of fungicides. As well as conventional fungicides, another chemical treatment involves treating wheat with a silicon solution or calcium silicate slag. Silicon helps the plant cells defend against fungal attack by degrading haustoria and by producing callose and papilla. With silicon treatment, epidermal cells are less susceptible to powdery mildew. ^[7]

Another way to control wheat powdery mildew is breeding in genetic resistance, using resistance genes to prevent infection. Over 100 formally and/or temporarily designated powdery mildew resistance genes/alleles have so far been identified in wheat. ^{[8] [9] [10]} However, Blumeria graminis can and has evolved to counteract the resistance provided by some alleles. ^[11]

Micromorphology

Description

The primary mycelium is first white, becoming pigmented. The secondary mycelium is dense, appearing woolly to felt-like. It occurs on the leaf in patches, often around chasmothecia. The original colour of mycelium is dingy greyish white to grey, which turns tan-coloured with age. The hyphal appressoria are described as nipple-shaped, occasionally lobe-shaped, occurring either singly or opposite in pairs. Conidia contain germ tubes, in two types: lateral primary germ tubes about 0.5x the width of the conidium lacking an appressorium, which appear within one hour; and the lateral or terminal germ tube which follows this, which is broader, straight or somewhat flexuous and extending to 1.25–3x the width of the conidium. These also have an elongated swollen tip. The chasmothecia (fruiting bodies) are surrounded by bristle-like secondary hyphae. Chasmothecial appendages are found in the lower half, and are simple and myceloid. The peridium of the chasmothecia is obscure and irregularly polygonal. Blumeria graminis has eight spores per ascus which are roughly ellipsoid and colourless. The asci are typically subcylindrical or saccate.

Measurements

Primary hyphal cells measure 30–55 x 3–7 µm. Secondary hyphal cells measure 220–500 x 3–7 µm. Hyphal appressoria are 3.5–7 µm wide. Conidiophores are 60–170 × 4–7 µm with foot cells measuring (20–)25–35(–40) × 5–7 µm. Conidia are (23–)28–40(–45) × (10–)14–18(–20.5) µm. The chasmothecia are 175–245(–260) µm in diameter when mature with peridium cells 8–20 µm in diameter. Asci are (50–)80–95(–105) × 20–45 µm with ascospores measuring 20–24 × 10–14 µm.

References

1. Liu, Miao; Braun, Uwe; Takamatsu, Susumu; Hambleton, Sarah; Shoukouhi, Parivash; Bisson, Kassandra R.; Hubbard, Keith (2021-05-20). "Taxonomic revision of Blumeria based on multi-gene DNA sequences, host preferences and morphology". Mycoscience. 62 (3): 143–165. doi:10.47371/mycosci.2020.12.003. ISSN   1340-3540. PMC   9157761 . PMID   37091321.
2. Huang, X. Q.; Hsam, S. L. K.; Zeller, F. J.; Wenzel, G.; Mohler, V. (2000). "Molecular mapping of the wheat powdery mildew resistance gene Pm24 and marker validation for molecular breeding:". Theoretical and Applied Genetics. 101 (3): 407–414. doi:10.1007/s001220051497. ISSN   0040-5752.
3. Braun, Uwe; Cook, Roger T. A. (2012). Taxonomic manual of the Erysiphales (powdery mildews). CBS biodiversity series. Utrecht: CBS-KNAW fungal biodiversity centre. ISBN   978-90-70351-89-2.
4. Wyand, Rebecca A.; Brown, James K. M. (2003). "Genetic and forma specialis diversity in Blumeria graminis of cereals and its implications for host-pathogen co-evolution". Molecular Plant Pathology. 4 (3): 187–198. doi:10.1046/j.1364-3703.2003.00167.x. ISSN   1364-3703.
5. Wicker, Thomas; Oberhaensli, Simone; Parlange, Francis; Buchmann, Jan P; Shatalina, Margarita; Roffler, Stefan; Ben-David, Roi; Doležel, Jaroslav; Šimková, Hana; Schulze-Lefert, Paul; Spanu, Pietro D; Bruggmann, Rémy; Amselem, Joelle; Quesneville, Hadi; Ver Loren van Themaat, Emiel (2013). "The wheat powdery mildew genome shows the unique evolution of an obligate biotroph". Nature Genetics. 45 (9): 1092–1096. doi:10.1038/ng.2704. ISSN   1061-4036.
6. Orton, Elizabeth S.; Brown, James K. M. (2016-05-31). "Reduction of Growth and Reproduction of the Biotrophic Fungus Blumeria graminis in the Presence of a Necrotrophic Pathogen". Frontiers in Plant Science. 7. doi: 10.3389/fpls.2016.00742 . ISSN   1664-462X. PMC   4885842 . PMID   27303429.
7. Bélanger, R. R.; Benhamou, Nicole; Menzies, J. G. "Cytological Evidence of an Active Role of Silicon in Wheat Resistance to Powdery Mildew (Blumeria graminis f. sp. tritici)" (PDF). www.siliforce.com. Archived from the original (PDF) on 2018-06-12. Retrieved 2025-10-09.
8. Wang, Bo; Meng, Ting; Xiao, Bei; Yu, Tianying; Yue, Tingyan; Jin, Yuli; Ma, Pengtao (2023-08-22). "Fighting wheat powdery mildew: from genes to fields". Theoretical and Applied Genetics. 136 (9): 196. doi:10.1007/s00122-023-04445-4. ISSN   1432-2242.
9. Chen, Xiangdong; Wang, Haobo; Fang, Kaiqiang; Ding, Guohui; Dong, Nannan; Dong, Na; Zhang, Man; Zang, Yihao; Ru, Zhengang (2025-06-12). "Genome-Wide Association Analysis Identifies Loci for Powdery Mildew Resistance in Wheat". Agronomy. 15 (6): 1439. doi: 10.3390/agronomy15061439 . ISSN   2073-4395.
10. Mapuranga, Johannes; Chang, Jiaying; Yang, Wenxiang (2022-12-16). "Combating powdery mildew: Advances in molecular interactions between Blumeria graminis f. sp. tritici and wheat". Frontiers in Plant Science. 13. doi: 10.3389/fpls.2022.1102908 . ISSN   1664-462X. PMC   9800938 . PMID   36589137.
11. Xiao, Jun; Liu, Bao; Yao, Yingyin; Guo, Zifeng; Jia, Haiyan; Kong, Lingrang; Zhang, Aimin; Ma, Wujun; Ni, Zhongfu; Xu, Shengbao; Lu, Fei; Jiao, Yuannian; Yang, Wuyun; Lin, Xuelei; Sun, Silong (2022). "Wheat genomic study for genetic improvement of traits in China". Science China Life Sciences. 65 (9): 1718–1775. doi:10.1007/s11427-022-2178-7. ISSN   1674-7305.