Blumeria graminis (powdery mildew of grasses and cereals)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Seedborne Aspects
- Plant Trade
- Detection and Inspection
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Blumeria graminis (DC.) Speer
Preferred Common Name
- powdery mildew of grasses and cereals
Other Scientific Names
- Erysiphe graminis DC.
- Oidium monilioides (Nees) Link
International Common Names
- Spanish: cenicilla de los cereales; oidio de los cereales
- French: blanc des cereales; blanc des graminees; oidium des cereales
Local Common Names
- Germany: Mehltau: Getreide
- ERYSGR (Blumeria graminis)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Fungi
- Phylum: Ascomycota
- Subphylum: Pezizomycotina
- Class: Leotiomycetes
- Order: Erysiphales
- Family: Erysiphaceae
- Genus: Blumeria
- Species: Blumeria graminis
Notes on Taxonomy and NomenclatureTop of page This fungus is the only species of the genus Blumeria but it has previously been treated as a species of Erysiphe. According to Braun (1987), it differs from all species of Erysiphe because its anamorph possesses unique features, for example, digitate haustoria, secondary mycelium with bristle-like hyphae and bulbous swellings of the conidiophores, and because of the structure of the ascocarps. Braun (1987) considers that, because of these differences, there should be a separation at generic level. Molecular sequence analyses proved the separate position of the powdery mildew on Poaceae and showed that Blumeria takes a basal position in the phylogenetic trees of the Erysiphales. Hence, Blumeria is only distantly related to Erysiphe and all other genera of the powdery mildew fungi (Saenz and Taylor, 1999; Mori et al., 2000; Braun et al., 2002).
DescriptionTop of page Primary mycelium branched, hyaline and uninucleate; hyphal cells (35-)40(-55) x 3-6 µm; appressoria nipple-shaped, solitary or in opposite pairs, 3.5-7 µm diam.; secondary mycelium consisting of bristle-like hyphae which are straight to falcate, thick-walled, 200-400 x 4-7 µm, hyaline, later ochraceous to rusty or reddish brown; conidiophores arising from the mycelium at a right angle with the host surface, erect, 60-90 x 4-7 µm, foot-cells 20-40 x 5-7 µm, with a basal bulbose swelling, ca 10-15 µm wide, followed by shorter cells, ca 12.5-25 µm long; conidia in chains, mostly uninucleate, occasionally binucleate, hyaline, ellipsoid-ovoid, limoniform, (20-)25-35(-45) x (8)12-16(-20) µm, germinating by a simple germ tube, terminal to lateral, straight to somewhat flexuous, ca 12-50 x 2.5-4 µm, after germination germ tube forming an appressorium in juxtaposition with the host cuticle, a hyphal peg penetrating the cuticle and the subcuticular wall and forming an haustorium in the epidermal cell; haustoria ellipsoid with long, finger-shaped appendages radiating from both ends (the fungus advances no further in plant tissue and the remainder of the mycelium, as well as the ascomata, are entirely extramatrical i.e. on the exterior of the host substratum). Ascomata (chasmothecia) immersed in the mycelial felt, at first globose, becoming strongly depressed, often cupulate, 110-280 µm diam., peridial cells obscure, irregularly polygonal, 8-20 µm diam., with simple, rarely branched appendages, few to numerous, in the lower half, usually shorter than the ascomatal diam., mycelioid, septate, hyaline to pigmented, thin-walled, smooth, asci 6-30, saccate-ovate to subcylindrical, short-stalked, 50-110 x 20-45 µm; usually 8-spored, sometimes 4-spored, but ascospores rarely fully developed; ellipsoid-ovoid, subhyaline to pale brown, 20-24 x 10-14 µm.
See also Kapoor (1967) and Braun (1987, 1995).
DistributionTop of page Although powdery mildew of cereals and grasses has a genuinely worldwide distribution, there appear to be fewer reports of it in South America than elsewhere. Powdery mildew is distributed widely in Europe and North America, and in China.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Kong and Dong, 1997; CABI/EPPO, 2004|
|-Beijing||Present||Duan et al., 1999|
|-Hebei||Present||Gao, 1997; CABI/EPPO, 2004|
|-Henan||Present||Wang et al., 1992; CABI/EPPO, 2004|
|-Nei Menggu||Present||CABI/EPPO, 2004|
|-Shanxi||Present||Sheng et al., 1993; CABI/EPPO, 2004|
|-Xinjiang||Present||CABI/EPPO, 2004; Zhang et al., 2014|
|Georgia (Republic of)||Present||CABI/EPPO, 2004|
|India||Present||Basandrai et al., 1996; CABI/EPPO, 2004|
|-Himachal Pradesh||Present||Sharma et al., 1996; CABI/EPPO, 2004|
|-Indian Punjab||Present||CABI/EPPO, 2004|
|-Jammu and Kashmir||Present||CABI/EPPO, 2004|
|-Madhya Pradesh||Present||CABI/EPPO, 2004|
|-Sikkim||Present||Srivastava, 1996; CABI/EPPO, 2004|
|-Tamil Nadu||Present||CABI/EPPO, 2004|
|-Uttar Pradesh||Present||CABI/EPPO, 2004|
|Iran||Present||CABI/EPPO, 2004; Abkhoo, 2015|
|Japan||Present||Morikawa, 1995; CABI/EPPO, 2004|
|Korea, Republic of||Present||Lee and Kim, 1990; CABI/EPPO, 2004|
|Nepal||Present||Ghimire and Pradhanang, 1996; CABI/EPPO, 2004|
|Saudi Arabia||Present||El-Meleig & Al-Rokibah, 1996; CABI/EPPO, 2004|
|Taiwan||Present||Tanda and Su, 1995; CABI/EPPO, 2004|
|Egypt||Present||El-Sayed et al., 1995; CABI/EPPO, 2004|
|Morocco||Present||Arifi, 1995; CABI/EPPO, 2004|
|South Africa||Present||CABI/EPPO, 2004|
|-Canary Islands||Present||Amano, 1986|
|Tunisia||Present||Cherif et al., 1994; Yahyaoui et al., 1997; CABI/EPPO, 2004|
|Western Sahara||Present||Amano, 1986|
|Zimbabwe||Present||Mtisi and Mashiringwani, 1995; CABI/EPPO, 2004|
|-British Columbia||Present||CABI/EPPO, 2004|
|-New Brunswick||Present||CABI/EPPO, 2004|
|-Newfoundland and Labrador||Present||CABI/EPPO, 2004|
|-Northwest Territories||Present||CABI/EPPO, 2004|
|-Nova Scotia||Present||Al-Mughrabi and Gray, 1996; CABI/EPPO, 2004|
|-Ontario||Present||Kasha, 1996; CABI/EPPO, 2004|
|-Prince Edward Island||Present||CABI/EPPO, 2004|
|-Yukon Territory||Present||CABI/EPPO, 2004|
|-District of Columbia||Present||CABI/EPPO, 2004|
|-Georgia||Present||Johnson et al., 1996; CABI/EPPO, 2004|
|-Kansas||Present||Sears et al., 1997; CABI/EPPO, 2004|
|-Kentucky||Present||Pearce et al., 1996; CABI/EPPO, 2004|
|-New Hampshire||Present||CABI/EPPO, 2004|
|-New Jersey||Present||CABI/EPPO, 2004|
|-New Mexico||Present||CABI/EPPO, 2004|
|-New York||Present||CABI/EPPO, 2004|
|-North Carolina||Present||CABI/EPPO, 2004|
|-North Dakota||Present||CABI/EPPO, 2004|
|-Ohio||Present||Gooding et al., 1997; CABI/EPPO, 2004|
|-Rhode Island||Present||CABI/EPPO, 2004|
|-South Carolina||Present||CABI/EPPO, 2004|
|-South Dakota||Present||CABI/EPPO, 2004|
|-West Virginia||Present||CABI/EPPO, 2004|
Central America and Caribbean
|Puerto Rico||Present||Amano, 1986|
|Argentina||Present||Molten et al., 1996; CABI/EPPO, 2004|
|Brazil||Present||Felicio et al., 1996; CABI/EPPO, 2004|
|-Mato Grosso do Sul||Present||CABI/EPPO, 2004|
|-Minas Gerais||Present||CABI/EPPO, 2004|
|-Rio Grande do Sul||Present||CABI/EPPO, 2004|
|-Sao Paulo||Present||CABI/EPPO, 2004|
|Chile||Present||Mellado et al., 1994; CABI/EPPO, 2004|
|Venezuela||Present||Schotman, 1989; CABI/EPPO, 2004|
|Austria||Present||Sykora et al., 1995; CABI/EPPO, 2004|
|Belgium||Present||Herman and Couvreur, 1994; CABI/EPPO, 2004|
|Bulgaria||Present||Dobrev and Tufa, 1995; CABI/EPPO, 2004|
|Croatia||Present||Koric, 1994; CABI/EPPO, 2004|
|Cyprus||Present||Kari, 1996; CABI/EPPO, 2004|
|Czech Republic||Present||Dreiseitl & Jarecka, 1997; Hanisova and Hanis, 1997; CABI/EPPO, 2004|
|Denmark||Present||Jorgensen et al., 1995; CABI/EPPO, 2004|
|Estonia||Present||Priiliin et al., 1996; CABI/EPPO, 2004|
|Faroe Islands||Present||CABI/EPPO, 2004|
|Finland||Present||Peusha et al., 1996; CABI/EPPO, 2004|
|France||Present||Steden et al., 1997; CABI/EPPO, 2004|
|Germany||Present||Sachs, 1995; CABI/EPPO, 2004|
|Hungary||Present||Sykora et al., 1995; CABI/EPPO, 2004|
|Italy||Present||Pasquini et al., 1996; CABI/EPPO, 2004|
|Lithuania||Present||Ruzgas and Lintkevicius, 1996; CABI/EPPO, 2004|
|Netherlands||Present||Timmer, 1996; CABI/EPPO, 2004|
|Norway||Present||Assveen and Gunnarstorp, 1996; CABI/EPPO, 2004|
|Poland||Present||Golebrink, 1995; CABI/EPPO, 2004|
|Russian Federation||Present||Terekhov et al., 1997; CABI/EPPO, 2004|
|-Central Russia||Widespread||CABI/EPPO, 2004|
|-Eastern Siberia||Widespread||CABI/EPPO, 2004|
|-Northern Russia||Widespread||CABI/EPPO, 2004|
|-Russian Far East||Widespread||CABI/EPPO, 2004|
|-Southern Russia||Widespread||CABI/EPPO, 2004|
|-Western Siberia||Widespread||CABI/EPPO, 2004|
|Slovakia||Present||Sekerkova, 1996; CABI/EPPO, 2004|
|Spain||Present||Marin et al., 1994; CABI/EPPO, 2004|
|Svalbard and Jan Mayen||Present||Amano, 1986|
|Sweden||Present||Lindblad, 1994; CABI/EPPO, 2004|
|Switzerland||Present||Anon, 1994; CABI/EPPO, 2004|
|UK||Present||Higginbotham et al., 1996; O'Hara and Brown, 1996; CABI/EPPO, 2004|
|-Northern Ireland||Present||Mercer & Ruddock, 2003|
|Ukraine||Present||Lisovoy and Parphenyuk, 1997; CABI/EPPO, 2004|
|Yugoslavia (former)||Present||Stojanovic et al., 1995; CABI/EPPO, 2004|
|Yugoslavia (Serbia and Montenegro)||Present||CABI/EPPO, 2004|
|Australia||Present||Whisson, 1996; CABI/EPPO, 2004|
|-New South Wales||Present||CABI/EPPO, 2004|
|-South Australia||Present||CABI/EPPO, 2004|
|-Western Australia||Present||CABI/EPPO, 2004|
|New Zealand||Present||Cromey & Hansen, 1992; CABI/EPPO, 2004|
Risk of IntroductionTop of page There are no known quarantine regulations on B. graminis perhaps because of its widespread distribution and airborne dissemination.
Hosts/Species AffectedTop of page B. graminis is found on numerous species comprising more than 100 genera of Poaceae, with the exception of the Maydeae, Andropogoneae, Zoysieae, Paniceae and Oryzeae (Dickson 1956; Amano, 1986).
Host Plants and Other Plants AffectedTop of page
|Avena sativa (oats)||Poaceae||Main|
|Bromus catharticus (prairiegrass)||Poaceae||Other|
|Elymus smithii (Colorado bluestem)||Poaceae||Other|
|Festuca arundinacea (tall fescue)||Poaceae||Other|
|Hordeum vulgare (barley)||Poaceae||Main|
|Lolium perenne (perennial ryegrass)||Poaceae||Main|
|Phalaris paradoxa (awned canary-grass)||Poaceae||Other|
|Poa pratensis (smooth meadow-grass)||Poaceae||Other|
|Poaceae (grasses)||Poaceae||Wild host|
|Secale cereale (rye)||Poaceae||Main|
|Triticum aestivum (wheat)||Poaceae||Main|
|Triticum turgidum (durum wheat)||Poaceae||Main|
Growth StagesTop of page Flowering stage, Fruiting stage, Seedling stage, Vegetative growing stage
SymptomsTop of page Powdery mildew appears in the form of white, later grey-tan areas on all aerial parts of cereals and grasses i.e. leaves, stems and ears, although leaves are most commonly infected. Initial symptoms are easily overlooked and take the form of chlorotic flecks on plant tissue. This is quickly followed by the development of white patches which produce masses of conidia (asexual spores) and assume a powdery appearance. If the plant is shaken even gently, clouds of conidia are released from the patches. Ascomata (fruit bodies forming sexual spores) may or may not form, but when they do, they occur late in the season and can be found embedded in the mildew colonies as tiny, dark-coloured dots.
List of Symptoms/SignsTop of page
|Inflorescence / lesions on glumes|
|Leaves / abnormal colours|
|Leaves / fungal growth|
|Roots / reduced root system|
|Stems / mycelium present|
Biology and EcologyTop of page B. graminis overwinters mainly as a mycelial mat on leaves of grasses and autumn-sown cereals. Although the ascomata produced during the late summer are fairly resistant to cold and drying out, they appear to be of secondary importance in overwintering and as a source of inoculum in the spring. This is because in temperate regions, fresh host plant material is nearly always available over the winter period. Nevertheless, in humid weather, ascomata release ascospores which can start infections on autumn-sown crops in the autumn and perhaps also in the spring. As temperatures rise in the spring, dormant mycelium commences growth and conidia are produced rapidly. Conidia usually germinate over a range of temperatures from about 3 to 31°C, although 15°C is probably optimal for germination, together with a relative humidity about 95%. Conidial germination is inhibited by free water. Under favourable conditions, fresh conidia can be found in about 7 days and are dispersed within the crop and further afield in the wind. Crucially, therefore, epidemics of powdery mildew will tend to occur during conditions of alternating wet and dry weather, with some wind to ensure dispersal on the conidia.
Mildew is encouraged by very early autumn sowing, especially in barley. In the autumn, heavily infected plants may be less resistant to winter frosts and plants may die. Cereals grown late in the autumn and spring may also be more prone to attack. Powdery mildew is also encouraged by excessive use of nitrogen fertilizer and can be particularly severe in dense crops grown in a sheltered, humid environment.
For further information, see Spencer (1978), Parry (1990) and Manners (1993).
Seedborne AspectsTop of page
Seed treatment with difenoconazole, followed by flutriafol, triticonazole and triadimenol was shown to achieve the highest fungal protection in wheat (Reis et al. 2008).
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Flowers/Inflorescences/Cones/Calyx||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Leaves||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Stems (above ground)/Shoots/Trunks/Branches||hyphae; spores||Yes||Yes||Pest or symptoms usually visible to the naked eye|
|Plant parts not known to carry the pest in trade/transport|
|Fruits (inc. pods)|
|Growing medium accompanying plants|
|True seeds (inc. grain)|
ImpactTop of page Powdery mildew is one of the most common and destructive diseases of cereals. Actual losses depend on the time of disease epidemic onset and its severity, and can at the extreme reach up to 60% (James, 1991; Oerke, 1994). Although it occurs in most, if not all, parts of the world where cereals are grown, it is not considered to be a major problem in every region. This disease can be very destructive to cereals, but generally seems to cause most damage in temperate latitudes, where economically important cereals are more frequently cultivated. However, powdery mildew can also be a limiting factor for cereal production in subtropical and tropical areas. Yield losses by powdery mildews are generally complex to estimate and depend on several factors such as climate, year, cropping system, cereal species and cultivar.
In some parts of Europe, powdery mildews are a limiting factor to the yield of cereals. In the UK, the Agricultural Development and Advisory Service (ADAS, 1980) estimated that increases in yield of winter barley achieved by controlling B. graminis infection in 1978 and 1979 ranged from 0.11 to 0.65 t/ha. Although Cook and King (1984) ranked B. graminis infection as the principal pathogen of spring barley in England and Wales, yield losses vary on a yearly basis. Cock (1975) estimated that losses in spring barley in 1974 and 1975 were 1.3% and 0.5%, respectively. From 1975 to 1978, powdery mildew was the most frequent foliar pathogen in barley and caused yield losses ranging from 2.8 (James et al., 1991) to 8.7% (King, 1977b). In the period 1976-1986, yield losses of 4-9% were recorded for powdery mildew in spring barley in England and Wales (Polley et al., 1993). Field tests in England have suggested that the effects of B. graminis f.sp. hordei infection on grain-filling in spring barley may be determined partly by temperature during the grain-filling period. Fungicides that controlled mildew increased the total grain yield much more in a warm environment (58.2%) than in a cool environment (17.7%). These results illustrated the potential risks involved in using data obtained under one set of circumstances to predict what will happen in another, especially when environments differ so greatly (Jenkyn, 1984).
Estimated yield losses for wheat grown in England and Wales in the period from 1970 to 1975 were 2.8% (King, 1977a), but from 1981 to 1988 yield losses of only 0.5% were estimated (James et al., 1991). In organic wheat, mildew led to yield losses of around 7% in 1991 (Yarham and Turner, 1992). Yield decreases of up to 30% (-1.61 t/ha) were correlated with the severity of mildew on leaf 2 between the watery and milky ripe (GS 71-75) development stages of wheat (Hardwick et al., 1994).
In Scotland, powdery mildew was by far the most important disease from 1970 to 1973, being responsible for average yield losses of 7.0% in barley (James et al., 1991). In wheat, studies carried out between 1970 and 1974 revealed losses due to powdery mildew of 1.7% (James et al., 1991).
The principal disease of barley in central Europe is powdery mildew (Oerke et al., 1994). Field trials with winter barley in Germany between 1975 and 1981 revealed yield losses of 11% due to powdery mildew (Kolbe, 1982). Despite the use of crop protection measures, Lutze et al. (1982) calculated that the average yield loss due to powdery mildew over 6 years was 5.3% (a range of 3.3 to 6.2% was estimated) in barley cultivated in the east of Germany. Based on a yield level of 7.5 t/ha, heavy infections by powdery mildew resulted in losses of 4.8% in wheat during 1969-79 in Germany (Anderl et al., 1984). In the Czech Republic, yield losses of 17% were reported in wheat growing under a severe infection pressure of powdery mildew (Benada and Vanova, 1984). The crop loss in wheat in the Netherlands despite control practices against powdery mildew in 1980 was 1% (Daamen, 1981). Analysis of epidemics showed mildew damage at growth stages GS 32-83 (second node to early dough) to be described by the simple function D = -0.0013 t/ha per colony-day of mildew per leaf, at yield levels of 7-9 t/ha and independently of wheat cultivar, year or nitrogen supply (Daamen, 1989). In Romania, crop losses due to B. graminis f.sp. tritici varied from 1 to more than 20% depending on the region in which it occurred (Ciurdarescu et al., 1987).
Powdery mildew is a destructive disease of wheat in the mid-Atlantic states of the USA in most years. For example, yield losses in Virginia ranging from 12 to 20% have been observed in susceptible cultivars (Griffey et al., 1993). In North Carolina, yield reductions of ca 17% were reported in the susceptible cultivar Saluda when disease severity reached 10% on the flag leaf by heading stage. It has been concluded that powdery mildew can limit yield in modern soft red winter wheat cultivars, although current levels of resistance in certain cultivars are sufficient to prevent large yield reductions (Leath and Bowen, 1989). In Kentucky, USA, an average yield loss of 20% was associated with powdery mildew over two experimental years in soft red winter wheat (Pearce et al., 1996).
Among the pathogens of wheat in Argentina, powdery mildew practically occurs every year in the wheat cropping area, particularly in the first growth stages and less frequently in later stages. In general, it is not economically important in the crop area of La Pampa Humeda, in contrast to areas with higher temperatures such as Santa Fe, Entre Rios and Chaco, where the disease also occurs at later growth stages and can therefore cause significant yield losses. However, no precise data on losses by powdery mildew is available for wheat in Argentina (Molteni, 1996). In field experiments carried out in the south of Brazil during 1981, powdery mildew reduced the yield of a wheat susceptible cultivar by 8% (Luz, 1984). In 1986, experimental results showed that yield losses attributed to the lack of fungicide control of powdery mildew varied from 20-23% (in susceptible cultivars) to 55% (in a highly susceptible wheat cultivar), when compared with conditions where the control was situated (Linhares, 1988).
Based on figures from the Chinese crop protection authorities, Teng (1986) quoted losses nationwide due to powdery mildew in wheat as 3.4%. According to the average wheat yield in China, the permissible loss was 1.7% (Lu and Gong, 1986).
In New Zealand, Cromey et al. (1992) reported losses in winter wheat of up to 63% following wheat diseases including powdery mildew infection. Infection of up to 70% leaf area damage resulted in a 40-60% reduction in grain yield in barley grown in Australia (Chan et al., 1990).
DiagnosisTop of page Because, under favourable conditions, powdery mildew can infect leaves and commence sporulating within 7-8 days, and is easily identified, specific diagnostic methods are usually not required. B. graminis is an obligate biotroph and cannot be cultured axenically.
Detection and InspectionTop of page Powdery mildew is easily detected in the crop since the white, fluffy colonies are easily seen on the foliage.
Prevention and ControlTop of page Cultural Control and Sanitary Methods
Since volunteer cereals act as overwintering sources of inoculum and stubble and crop debris may be infested with cleistothecia, eradication of volunteers and disposing of stubble and debris are important aspects of cultural control. Isolation of autumn-sown and spring-sown cereals (i.e. not growing them too close together) will reduce the risk of infection of the autumn-sown crop spreading to the spring-sown crop. In addition, because nitrogen fertilizer promotes lush crop growth and encourages mildew development, excessive use of nitrogen should be avoided.
Host-plant resistance is very important in the control of powdery mildew on cereals. A wide range of resistance to powdery mildew is exhibited by varieties of wheat, barley and oats, and in those countries where mildew is widespread, it is prudent to choose a variety with a good disease resistant rating. If the variety grown has poor resistance to powdery mildew, careful crop monitoring will be necessary in order to optimise the timing of fungicide applications.
Spread of mildew from one field to another can be reduced by the correct diversification of varieties. In the UK, the National Institute of Agricultural Botany (NIAB) produces a leaflet on Diversification Schemes which gives information on good combinations of varieties. Growing mixtures of varieties is also an option to reduce mildew (Chin and Wolfe, 1984).
Rubiales et al. (2001) found that chromosomal addition lines of Hordeum vulgare and Hordeum chilense possessed resistance to wheat powdery mildew. This resistance was expressed as a reduction of disease severity and is of broad genetic basis, conferred by gene (s) present on different chromosomes of both H. vulgare and H. chilense. This resistance may be useful in breeding new wheat varieties with resistance to powdery mildew. In addition, a powdery mildew resistance gene, originating from wild emmer wheat (Triticum dicoccoides) accession C20, from Israel, was successfully transferred to hexaploid wheat through crossing and backcrossing (Lin et al., 2002). Genetic analyses revealed that a single dominant gene controls the powdery mildew resistance at the seedling stage. The gene was assigned to chromosome area 5BS and appears to be a new gene, designated PM30.
A range of spring barley mixtures including one set made from cultivars grown in the UK and one from cultivars grown in Poland, were examined, along with their component cultivars, in nine trials at Scottish Crop Research Institute, Dundee, UK, or at the Experimental Plant Breeding Station of the IHAR, Bakow near Kluczbork, Poland, over five seasons. In four trials where inoculum pressure was controlled, mixtures reduced infection more at lower inoculum pressures, but this did not translate into yield benefit. Smaller plots increased mildew in monocultures but not mixtures. Fertilizer levels increased mildew levels but did not affect mixture efficacy. There were large differences between both Polish and UK germplasm, and between Polish and UK trial sites, but the performance of the mixtures compared with their respective monoculture components was similar within both germplasm groups and trial sites. Mixtures reduced lodging and affected plant height and heading date. The advantages of mixtures for improving yield, reducing fungicide applications and improving agronomic characteristics was demonstrated and there seems to be great potential for their further improvement and exploitation.
Fungicides are widely used in the control of powdery mildew in cereals. Mildew on wheat and barley can be controlled using morpholines (e.g., fenpropidin), triazoles (e.g., tebuconazole and cyproconazole) and the more recent strobilurin fungicides. Differences in the efficacy of fungicides used in mildew control are due, in large part, to the development of isolates of B. graminis which are tolerant to fungicide groups. Tolerance has been detected to the triazoles, for example, flutriafol, propiconazole and triadimefon. However, these are often combined with another active ingredient, commonly a morpholine such as tridemorph, in order to increase efficacy and reduce pressure on the pathogen to produce triazole-tolerant isolates. Resistance to strobilurin fungicides has been detected in isolates from B. graminis f.sp. tritici from commercial crops in England and Germany (Fraaije et al., 2002). These workers developed a quantitative real-time PCR diagnostic procedure for the early detection of resistance genes at low frequency which, if used with risk evaluation, would be invaluable for further resistance risk assessment and validation of anti-resistance strategies.
Mildew infection on oats can also be controlled using morpholines and triazoles, although in some countries such as the UK, the range of fungicides approved for oats is limited compared to other cereals. A new fungicide, Falcon 460 EC containing the new active ingredient spiroxamine, was introduced in Slovenia in 2000 for the control of a range of diseases including powdery mildew on cereals (Kraner, 2001). In addition, simeconazole (2-[4-fluorophenyl)-1-(1H-1,2, 4-triazol-l-yl)3-trimethylsilylpropan-2-01), a novel triazole fungicide with broad spectrum activity was launched as a new seed treatment (Tsuda et al., 2000). It has activity against powdery mildew (B. graminis) and has been shown to increase wheat yields by 10% compared to untreated crops.
Computer based decision support systems (DSS), for example, EPIPRE, have been developed to aid fungicide spray recommendations for the main diseases on wheat including powdery mildew (Forrer, 1992) and a DSS for disease in spring barley is under development
For further information, see Parry (1990).
ReferencesTop of page
Anderl A; Mangstl A; Reiner L, 1984. The effect of fungicides on yield and yield structure in winter wheat, investigated on the database or ISPFLANZ. Bayerisches Landwirtschaftliches Jahrbuch, 61(6):816-849
Braun U, 1995. The Powdery Mildews (Erysiphales) of Europe. Jena, Germany: Gustav Fischer Verlag, 337 pp.
Cherif M; Harrabi M; Morjane H, 1994. Distribution and importance of wheat & barley diseases in Tunisia 1989-1991. Rachis, 13:25-34.
Cock LJ, 1975. The control of cereal diseases in the UK. In: Proceedings of the 8th British Insecticide and Fungicide Conference, Brighton, UK: BCPC, 859.
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