Genetics of Powdery Mildew Resistance in Barley

Jørgensen, J. Helms; Wolfe, Martin S.

doi:10.1080/07352689409701910

Cited by 304 publications

(264 citation statements)

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“…This finding is in agreement with the results of the previous study in which the putative presence of this resistance was postulated based on tests using 23 differential isolates (Czembor 2000). This is the first rapport about discovery of spontaneous Mlo resistance in barley landrace originating from a country other than Ethiopia (Jørgensen 1971(Jørgensen , 1992 and Turkey (Czembor and Frese 2001, unpubl. data).…”

Section: Discussionsupporting

confidence: 92%

“…Because of this, the durability of resistance genes may be increased by use of multiline cultivars, by combining (pyramiding) different resistance genes into one variety and by deploying many cultivars with different resistance genes in space (cultivar mixtures) or time (winter versus spring barley) (Wolfe and McDermott 1994, Finckh et al 1999, Jalli et al 1999). In addition, there are still many resistance genes that have not been exploited so far, and new sources of resistance are still being found in barley landraces and barley wild relatives (Jørgensen 1994, Dreiseitl and Bockelman 1997, Czembor 2001. North Africa, including Libya, is characterised by big contrast in its natural conditions because of their mountainous topography and big contrasts in climate (transitional location between the Mediterranean winter-rain zone and the Sahara desert).…”

Section: Parentsmentioning

confidence: 99%

“…About 1970, it was also discovered as a spontaneous gene in barley landraces from Ethiopia collected by German expeditions in the 1930s. In 1985, Negassa described Mlo resistant barley landraces collected in southern Ethiopia (Jørgensen 1971, 1994, Negassa 1985, Schwarzbach 1998. Currently 25 different mlo resistance alleles are known.…”

Section: Parentsmentioning

confidence: 99%

“…Currently 25 different mlo resistance alleles are known. All of them with exception of mlo11 were produced by mutagenesis (Jørgensen 1994, Schwarzbach 1998. The first in Europe Mlo resistant barley variety Atem (released in The Netherlands in 1979) derived its resistance (mlo11) from the Ethiopian landrace L92.…”

Section: Parentsmentioning

confidence: 99%

“…Identification of powdery mildew resistance genes based on tests performed on seedlings using isolates with different virulence spectra is effective and sufficient for breeders and pathologist needs (Brückner 1964, Dreiseitl 1999, Dreiseitl and Jørgensen 2000. However, confirmation of putative resistance genes or alleles can only be established through the evaluation of progeny from crosses among appropriate genotypes (Jørgensen 1994, Czembor and Johnston 1999. Vavilov (1926) proposed that the region of Mediterranean Sea is major center of crop origin.…”

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confidence: 99%

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Selections from barley landrace collected in Libya as new sources of effective resistance to powdery mildew (Blumeria graminis f.sp. hordei)

Czembor¹,

Czembor²

2002

PLANT SOIL ENVIRON

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Powdery mildew on barley (Hordeum vulgare L.) caused by the pathogen Blumeria graminis f.sp. hordei occurs worldwide and can result in severe yield loss. Because agronomical methods to control the disease are not completely effective, cultivars with genetic resistance are needed. Therefore, there is a need to describe new sources of genes that confer resistance to barley powdery mildew. This study was conducted to determine the genetic basis of resistance to powdery mildew in three selections 995-1-1, 995-1-2, 995-1-3 from barley landrace 995 (ICB 112840) collected in Al Aziziyah district, Tripolitania, Libya. Landrace originated from International Center for Agricultural Research in the Dry Areas ICARDA, Aleppo, Syria. To determine the number of genes, the types of genes action and the gene loci in tested lines two types of crosses were made: (1) the lines were crossed to the susceptible cultivar Pallas, (2) the lines were crossed with Pallas isoline P22 carrying gene mlo5. The parents and progeny F 2 were evaluated with isolate R303.1 for the powdery mildew resistance. Based on segregation ratios we found that resistance in these three selections was determined by a single recessive gene allelic to the Mlo locus occurring in Pallas isoline P22. In addition tested lines showed resistance reaction type 0(4) characteristic only for genes mlo. The value of new identified sources of highly effective powdery mildew resistance to breeding programs and barley production is discussed.

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Section: Discussionsupporting

confidence: 92%

Section: Parentsmentioning

confidence: 99%

Section: Parentsmentioning

confidence: 99%

Section: Parentsmentioning

confidence: 99%

mentioning

confidence: 99%

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Selections from barley landrace collected in Libya as new sources of effective resistance to powdery mildew (Blumeria graminis f.sp. hordei)

Czembor¹,

Czembor²

2002

PLANT SOIL ENVIRON

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Powdery Mildews

Ridout

2009

Encyclopedia of Life Sciences

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Powdery mildews are an important group of parasitic fungi causing disease in over 7600 species of host plants. They are obligate biotrophic parasites, obtaining their nutrients from the host through intracellular feeding structures known as haustoria. Many species of powdery mildews have a high degree of host specialization, infecting only one or a few closely related host genera. Some powdery mildews have well‐documented gene‐for‐gene (GFG) resistance interactions with their host plant, revealing information about the nature of host specificity. This article focuses on the interactions between powdery mildews and the host plant. Events in the establishment of haustoria and biotrophy are reviewed and their influence of infection on host metabolism described. GFG, durable mlo and nonhost‐resistance mechanisms are also described. Key Concepts Importance of powdery mildews : Powdery mildews are extremely successful fungal parasites. Over 700 species have been described infecting over 7600 species of host plants, many of which are important crops species. Chemicals (fungicides) and resistance genes are used against them, but powdery mildews have the ability to rapidly adapt and defeat these control measures. Obligate biotrophy : All powdery mildews are obligate biotrophs, requiring a living host to grow and reproduce. Haustoria : The feeding structures produced by powdery mildews to obtain nutrients from epidermal cells of the host plants. Host specificity : Many powdery mildews have a high degree of host specialization, and can only grow on one or a few closely related plant genera. Infection can even be restricted to single genotypes of a specific host, as typified by gene‐for‐gene (GFG) resistance. GFG resistance : GFG resistance has been extensively investigated in the interaction between barley powdery mildew ( Blumeria graminis f. sp. hordei ) and the host plant, barley. In GFG resistance, an avirulence ( avr ) gene in the parasite matches a resistance ( R ) gene in the host causing a recognition event that triggers defence responses and prevents infection by the parasite. If either the avr gene or the R gene is lacking, the parasite is not recognized and can become established as a parasite. In barley, over 85 powdery mildew R genes have been described, and over 25 avr gene loci have been mapped in Bgh. mlo resistance : A loss‐of‐function mutation in the barley MLO protein results in failure of Bgh to establish a successful infection. mlo resistance has been widely used in barley breeding, and has so far proved to be durable. Nonhost resistance : Plants are resistant to most invading pathogens, a feature described as nonhost resistance (NHR). Only those adapted microbes that are able to overcome this NHR are able to infect and become pathogens. The extreme specificity of some powdery mildew/host interactions has enabled investigation into the basis of NHR. A series of pen Arabidopsis mutants with enhanced penetration by nonadapted Bgh have been defined. Genes coding for pen1‐pen3 have been identified, enabling key proteins required for NHR to be identified.

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