Powdery mildew (barley)

Powdery mildew is a fungal disease of barley caused by "Blumeria graminis" f. sp. "hordei". The disease has a worldwide distribution and is most damaging in cool, wet climates. The host range of the form species "hordei" is restricted to barley and other "Hordeum species".cite book
last = Wiese
first = M.V.
title = Compendium of wheat diseases
publisher = American Phytopathological Society
date = 1987
pages = 124 pp ] cite book
last = Martens
first = J.W.
coauthors = W.L. Seaman, T.G. Atkinson
title = Diseases of field crops in Canada
publisher = Canadian Phytopathological Society
date = 1984
pages = 160 pp ]

Symptoms

At first, powdery mildew can be observed as small greyish patches of fluffy fungal growth (mycelium) on the upper surface of the lower leaves. These spots resemble small cushions of white powder. Leaf tissue on the opposite side of an infected leaf turns pale green to yellow. The fungus only infects the epidermal layer and can be easily scrapped off with a fingernail. Infections can also occur on the leaf sheaths and ears. Leaves remain green and active for some time following infection, then gradually become chlorotic and die off. As the disease progresses, the mycelium often becomes dotted with minute black points (cleistothecia), which are the sexual fruiting bodies of the fungus.

Disease cycle

The fungus ovewinters as cleistothecia on straw, and in milder climates, also as mycelium and conidia on stubble and straw or volunteer barley and certain grasses. Windborne ascospores or conidia are the primary inoculum and can be dispersed over considerable distances. Infection by conidia requires high humidity, but not free water on the leaf surface. Sporulation and spore dispersal are favored by drier conditions. Thus the disease does well under alternating wet and dry conditions. Production of conidia declines markedly as the colony ages. Cleistothecia develop on older leaves as the plant matures. Low temperatures, together with the wetting of the cleistothecia for at least 72 hours, induces the maturations of the ascospores. Ascospores are released following rains, but are relatively sparse in comparison to the condia.

External links

Extension publications

* [http://209.85.165.104/search?q=cache:odp29TY_Ee8J:archives.eppo.org/EPPOStandards/PP2_GPP/pp2-11-e.doc+barley+diseases+eppo&hl=en&ct=clnk&cd=4&gl=us EPPO - Europe]
* [http://www.sac.ac.uk/consultancy/cropclinic/clinic/diseases/barleymildew Europe: Scotland]
* [http://www.ag.ndsu.edu/pubs/plantsci/smgrains/pp894w.htm US: North Dakota]
* [http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=108 US: Oregon]

Research articles

cite journal
last = Blatter
first = R.H.E
coauthors = J.K.M. Brown, M.S. Wolfe
title = Genetic control of the resistance of Erysiphe graminis f.sp. hordei to five triazole fungicides
journal = Plant Pathology
volume = 47(5)
pages = 570–579
date = 1998
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.1998.00276.x
doi = 10.1046/j.1365-3059.1998.00276.x

cite journal
last = Bousset
first = L.
coauthors = M.S. Hovmøller, V. Caffier, C. de Vallavieille-Pope, H. Østergård
title = Observed and predicted changes over eight years in frequency of barley powdery mildew avirulent to spring barley in France and Denmark
journal = Plant Pathology
volume = 51(1)
pages = 33–44
date = 2002
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.0032-0862.2001.00654.x
doi = 10.1046/j.0032-0862.2001.00654.x

cite journal
last = Bousset
first = L.
coauthors = B. Schaeffer, C. de Vallavieille-Pope
title = Effect of early infection on pathotype frequencies in barley powdery mildew (Blumeria graminis f.sp. hordei) populations in field plots
journal = Plant Pathology
volume = 50(3)
pages = 317–324
date = 2001
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.2001.00532.x
doi = 10.1046/j.1365-3059.2001.00532.x

cite journal
last = Boyd
first = L.A.
coauthors = P.H. Smith, R.M. Green, J.K.M. Brow
title = The relationship between the expression of fefense-related Genes and mildew development in barley
journal = MPMI
volume = 7
pages = 401–410
date = 1994
url = http://www.apsnet.org/mpmi/pdfs/1994/Microbe07-401.pdf

cite journal
last = Caffier
first = V
coauthors = T. Hoffstadt M. Leconte, C. de Vallavielle-Pope
title = Seasonal changes in pathotype complexity in French populations of barley powdery mildew
journal = Plant Pathology
volume = 45(3)
pages = 454–468
date = 1996
url = http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-3059.1996.d01-150.x
doi = 10.1046/j.1365-3059.1996.d01-150.x

cite journal
last = Dreiseitl
first = A.
coauthors = A. Dinoor, E. Kosman
title = Virulence and Diversity of Blumeria graminis f. sp. hordei in Israel and in the Czech Republic
journal = Plant Dis.
volume = 87
pages = 99
date = 2006
url = http://www.apsnet.org/pd/search/2006/pd-90-1031.asp

cite journal
last = Duggal
first = V.
coauthors = G.J. Jellis, T.W. Hollins, R. Stratford
title = Resistance to powdery mildew in mutant lines of the susceptible wheat cultivar Hobbit 'sib'
journal = Plant Pathology
volume = 49(4)
pages = 468–476
date = 2000
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.2000.00471.x
doi = 10.1046/j.1365-3059.2000.00471.x

cite journal
last = El-Zahaby
first = H.M.
coauthors = G. Gullner, Z. Király
title = Effects of powdery mildew infection of barley on the ascorbate-glutathione cycle and other antioxidants in different host-pathogen interactions
journal = Phytopathology
volume = 85
pages = 1225–1230
date = 1995
url = http://www.apsnet.org/phyto/PDFS/1995/Phyto85n10_1225.PDF
doi = 10.1094/Phyto-85-1225

cite journal
last = Fraaije,
first = B.A.
coauthors = J.A. Butters, J.M. Coelho, D.R. Jones, D.W. Hollomon
title = Following the dynamics of strobilurin resistance in Blumeria graminis f.sp. tritici using quantitative allele-specific real-time PCR measurements with the fluorescent dye SYBR Green I
journal = Plant Pathology
volume = 51(1)
pages = 45–54
date = 2002
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.0032-0862.2001.00650.x
doi = 10.1046/j.0032-0862.2001.00650.x

cite journal
last = Haugaard
first = H.
coauthors = H.J. Lyngs Jørgensen, M.F. Lyngkjær, V. Smedegaard-Petersen, D.B. Collinge
title = Control of Blumeria graminis f.sp. hordei by treatment with mycelial extracts from cultured fungi
journal = Plant Pathology
volume = 50(5)
pages = 552–560
date = 2001
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.2001.00595.x
doi = 10.1046/j.1365-3059.2001.00595.x

cite journal
last = Heide
first = M.
coauthors = V. Smedegaard-Petersen
title = Common antigens between barley and barley powdery mildew and their relation to resistance and susceptibility
journal = CJPP
volume = 7
pages = 341–346
date = 1985
url = http://www.cps-scp.ca/download/cjpp-archive/Vol7/CJPP7(4)341-346(1985).pdf

cite journal
last = Hückelhoven
first = R.
coauthors = K.-H. Kogel
title = Tissue-specific superoxide generation at interaction sites in resistant and susceptible near-isogenic barley lines attacked by the powdery mildew fungus (Erysiphe graminis f. sp. hordei)
journal = MPMI
volume = 11
pages = 292–300
date = 1998
url = http://www.apsnet.org/mpmi/PDFS/1998/0123-01R.pdf

cite journal
last = O'Hara
first = R.B.
coauthors = J.K.M. Brown
title = Immigration of the barley mildew pathogen into field plots of barley
journal = Plant Pathology
volume = 45(6)
pages = 1071–1076
date = 1996
url = http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-3059.1996.d01-192.x
doi = 10.1046/j.1365-3059.1996.d01-192.x

cite journal
last = O'Hara
first = R.B.
coauthors = J.K.M. Brown
title = Spatial aggregation of pathotypes of barley powdery mildew
journal = Plant Pathology
volume = 46(06)
pages = 969–977
date = 1997
url = http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-3059.1997.d01-84.x
doi = 10.1046/j.1365-3059.1997.d01-84.x

cite journal
last = O'Hara
first = R.B.
coauthors = J.K.M. Brown
title = Movement of barley powdery mildew within field plots
journal = Plant Pathology
volume = 47(4)
pages = 394–400
date = 1998
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.1998.00270.x
doi = 10.1046/j.1365-3059.1998.00270.x

cite journal
last = O'Hara
first = R.B.
coauthors = B.J. Nielsen, H. Østergård
title = The effect of fungicide dose on the composition of laboratory populations of barley powdery mildew
journal = Plant Pathology
volume = 49(5)
pages = 558–566
date = 2000
url = http://www.blackwell-synergy.com/doi/full/10.1046/j.1365-3059.2000.00496.x
doi = 10.1046/j.1365-3059.2000.00496.x

cite journal
last = Oslash;stergård
coauthors = M.F. Lyngkjær
title = Interaction between powdery mildew and barley with mlo5 mildew resistance
journal = Plant Pathology
volume = 47(3)
pages = 252–258
date = 1998
url = http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-3059.1998.00234.x
doi = 10.1046/j.1365-3059.1998.00234.x

cite journal
last = Schiffer
first = R.
coauthors = R. Görg, B. Jarosch, U. Beckhove, G. Bahrenberg, K.-H. Kogel, P. Schulze-Lefert
title = Tissue dependence and differential cordycepin sensitivity of race-specific resistance responses in the barley-powdery mildew interaction
journal = MPMI
volume = 10
pages = 830–839
date = 1997
url = http://www.apsnet.org/mpmi/PDFS/1997/0701-01R.pdf

cite journal
last = Vallélian-Bindschedler
first = L.
coauthors = J-P. Métraux, P. Schweizer
title = Salicylic acid accumulation in barley is pathogen specific but not required for defense-gene activation
journal = MPMI
volume = 11
pages = 702–705
date = 1998
url = http://www.apsnet.org/mpmi/PDFS/1998/0422-01N.pdf

cite journal
last = Yahyaoui
first = A.H.
coauthors = M. Reinhold, A.L. Scharen
title = Virulence spectrum in populations of the barley powdery mildew pathogen, Erysiphe graminis f. sp. hordei in Tunisia and Morocco in 1992
journal = Plant Pathology
volume = 46(1)
pages = 139–146
date = 1997
url = http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-3059.1997.d01-11.x
doi = 10.1046/j.1365-3059.1997.d01-11.x

References