Nejvíce citovaný článek - PubMed ID 32825722
Specific Resistance of Barley to Powdery Mildew, Its Use and Beyond. A Concise Critical Review
Genetic resistance is a sustainable way to protect crops from diseases, and breeding resistant varieties is a key objective. However, diseases are caused by pathogens with different life cycles, and the importance of individual evolutionary forces plays a key role in the adaptation of their populations. Therefore, strategies for the use of genetic resistance resources can vary depending on the plant pathosystem. Numerous major genes confer hypersensitive resistance to powdery mildew-one of the most common diseases in barley-but these genes conform to the gene-for-gene system of an extremely diverse and adaptable pathogen. When such resistance genes are transferred into commercial varieties, their efficiency in the field is soon overcome and replacement with newly developed resistant varieties can be slow. Hence, specific resistance genes should not be used in barley breeding programs. Only one monogenic, non-hypersensitive, non-specific and durable major resistance Mlo is known. This predominates in Central and Western European spring varieties and should be widely adopted by barley breeders elsewhere and in other crops where such type of resistance is found. In this paper, the relevant aspects involved in breeding barley resistant to powdery mildew are discussed, with conclusions supported by practical examples. Additionally, future directions for barley improvement are proposed.
- Klíčová slova
- Blumeria hordei, Hordeum vulgare, boom-and-bust cycle, durable resistance, gene postulation, major resistance genes, specific resistance,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Mlo is a well-known broad-spectrum recessively inherited monogenic durable resistance to powdery mildew caused by Blumeria hordei found first in barley, originally in an induced mutant in 1942 and later in other mutants and also in Ethiopian landraces. The first commercial varieties possessing Mlo resistance were released during 1979-1986, but these often showed symptoms of necrotic leaf spotting associated with reduced grain yield. However, this yield penalty was successfully reduced by breeding Mlo-resistant varieties of spring barley predominate in Europe; for example, in the Czech Republic, their ratio surpassed 90% of the total number of newly released varieties. However, outside Europe, Mlo-varieties are not yet popular and can be exploited more widely. Winter barley varieties are generally non-resistant, but the use of Mlo for their breeding is controversial despite the limited adaptability of the pathogen to this resistance. The renewal of mechanically disturbed epidermal plant cell walls, including the penetration of mildews, is common in plants, and the Mlo-type resistance is exploited in many other crop species, including wheat.
- Klíčová slova
- Blumeria hordei, Hordeum vulgare, Mlo resistance, barley, durable resistance, powdery mildew, resistance gene postulation, virulence frequency,
- Publikační typ
- časopisecké články MeSH
Barley is an important crop grown on almost 49 Mha worldwide in 2021 and is particularly significant in Europe where powdery mildew is the most frequent disease on susceptible varieties. The most suitable way to protect crops is by exploiting genetic resistance. However, the causal agent Blumeria hordei is an extremely adaptable pathogen. The aims of this research were to increase our knowledge of the rapidly changing pathogen population and detect rare virulences. Random samples of the pathogen were obtained from the air by means of a mobile spore sampler. Spores were collected by driving across the Czech Republic in 2019, 2021 and 2023, and 299 isolates were analyzed on 121 host varieties. No infection occurred on 35 differentials, rare virulence was recorded on 31 varieties and a higher virulence frequency was found on 55 differentials. A core set of differentials along with four additional varieties distinguishes 295 pathotypes (Simple Index = 0.987) and the virulence complexity of isolates varied from 4 to 19 with an average of 10.39. The detection of new virulences, the increasing frequency of previously rare virulences and high pathotype diversity as well as high virulence complexity confirm that using nonspecific durable resistance is crucial for successfully breeding commercial varieties.
- Klíčová slova
- Blumeria graminis f. sp. hordei, Hordeum vulgare, barley, powdery mildew, resistance genes, reverse octal notation, virulence complexity, virulence frequency,
- Publikační typ
- časopisecké články MeSH
Plant research and breeding depends on plant genotypes; therefore, genotype authenticity of accessions is the basic requirement for users of gene banks. Surprisingly, this extremely important topic is rarely reported in the scientific community. Non-authentic are accessions that are mislabelled and undesirable genotypes of heterogeneous accessions. In barley, we try to uncover both named problems on the basis of postulated major powdery mildew resistance genes. These are diverse, environmentally stable and their use is well documented and suitable for genotype characterization. In this contribution, we postulate resistance genes in 15 varieties represented by 157 derived lines of 32 accessions originating from seven foreign gene banks and compare these findings with previous results including those 15 identically labelled varieties from our domestic gene bank. We found that 37.5% of the gene bank accessions investigated herein were heterogeneous, and at least 20.0% were mislabelled. A large-scale molecular characterisation of varieties is now being carried out, and using authentic varieties must be one of the key requirements. Therefore, accessions of each variety from a minimum of three gene banks whose identity has been verified by reliable methods should be compared before starting new experiments. These will involve molecular varietal characterisation to serve as a foundation for future plant science research and effective crop improvement.
Barley is an important crop grown annually on about 55 Mha and intensively cultivated in Europe. In central and north-western Europe, spring and winter barley can be grown in similar environments which creates suitable conditions for the development of barley pathogens, including Blumeria graminis f. sp. hordei, the causal agent of powdery mildew. Apart from pesticide application, it can be controlled by inexpensive and environmentally-friendly genetic resistance. In this contribution, results of the resistance gene identification in 58 barley cultivars to powdery mildew are presented. In 56 of them their resistances were postulated and in two hybrid cultivars a recently developed method of gene identification was used. In total, 18 known resistance genes were found and several unknown genes were detected. In spring barley, a gene of durable resistance mlo is still predominant. MlVe found in winter SU Celly was the only new resistance gene recorded in barley cultivars registered in the Czech Republic in this time span. Since 2001 eight new genes of specific resistance have been identified in cultivars registered in the country and their response under field conditions is discussed, including the corresponding responses of the pathogen population due to directional selection. Different strategies for breeding spring and winter barley are recommended.
- Klíčová slova
- Blumeria graminis f. sp. hordei, Hordeum vulgare, infection response arrays, pathogen isolates, resistance gene postulation,
- MeSH
- ječmen (rod) * genetika MeSH
- nemoci rostlin genetika MeSH
- šlechtění rostlin MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
- Evropa MeSH
Cultivation of resistant varieties is an environmentally friendly and inexpensive method of crop protection. Numerous alleles of specific disease resistance occur in cereals and other crops, and knowledge of their presence in individual varieties has wide utilization in research and practice. Postulation based on phenotyping host-pathogen interactions and the gene-for-gene model is a common way of identifying these genes. The same technique and design of tests are used for postulating virulence when pathogen populations are studied. Powdery mildews caused by different formae speciales of Blumeria graminis (Bg) are important cereal diseases. In this contribution, experimental methods are described that use a model organism Bg f. sp. hordei, which can be employed for other cereal mildews and possibly rusts. It includes illustrations and a summary of our long-term practical experience. It also critically evaluates the benefits of leaf segment tests compared with screening whole plants.
- Klíčová slova
- Blumeria graminis f. sp. hordei, Hordeum vulgare, barley powdery mildew, biotrophic pathogens, cereals, resistance gene postulation,
- Publikační typ
- časopisecké články MeSH
The main problems of crop gene banks comprise heterogeneity of accessions, resulting from mechanical admixtures or out-crossing during their multiplication, and especially the mislabeling of accessions. These discrepancies can adversely affect the results of many expensive research and breeding projects that are based on the use of gene bank resources. To tackle these problems, 860 single-plant progenies (SPPs) of 172 accessions of the Czech winter barley core collection were grown and tested with a set of 53 isolates representing the global virulence/avirulence diversity of powdery mildew. Seventy-one resistance phenotypes encompassed the diversity of known specific resistances and their combinations. Based on testing groups of five SPPs, 94 accessions had one phenotype found in all five SPPs (homogeneous accessions), whereas in 78 accessions (45.3%) more than one phenotype was identified (heterogeneous accessions). In three varieties, specific resistances against the whole set of isolates were detected, but due to high adaptability of the pathogen, they are not recommended for breeding resistant cultivars. Selected SPPs were integrated in the gene bank and are now a reliable source of genotypically pure seed with defined powdery mildew resistance genes that can be used by breeders and researchers. The results obtained can be used to verify authenticity of accession genotype and pedigree, particularly for older varieties for which no other original criteria are available.
Powdery mildew (Blumeria graminis f. sp. tritici) is a common pathogen of bread wheat (Triticum aestivum L.), and genetic resistance is an effective and environmentally friendly method to reduce its adverse impact. The introgression of novel genes from wheat progenitors and related species can increase the diversity of disease resistance and accumulation of minor genes to improve the crop's resistance durability. To accomplish these two actions, host genotypes without major resistances should be preferably used. Therefore, the main aim of this study was to carry out seedling tests to detect such resistances in a set of wheat accessions from the Czech gene bank and to group the cultivars according to their phenotype. Ear progenies of 448 selected cultivars originating from 33 countries were inoculated with three isolates of the pathogen. Twenty-eight cultivars were heterogeneous, and 110 cultivars showed resistance to at least one isolate. Fifty-nine cultivars, mostly from Northwest Europe, were resistant to all three isolates were more than three times more frequently recorded in spring than in winter cultivars. Results will facilitate a rational and practical approach preferably using the set of cultivars without major resistances for both mentioned methods of breeding wheat cultivars resistant to powdery mildew.
- Klíčová slova
- Blumeria graminis f. sp. hordei, Blumeria graminis f. sp. tritici, infection response arrays, resistance postulation, single ear progenies,
- Publikační typ
- časopisecké články MeSH
Powdery mildew, a common cereal disease caused by the fungus Blumeria graminis, is a major limiting factor of barley production and genetic resistance is the most appropriate protection against it. To aid the breeding of new cultivars and their marketing, resistance genes can be postulated in homogeneous accessions. Although hybrid cultivars (F1) should be homogeneous, they are often not genetically uniform, especially if more than two genotypes are involved in their seed production or due to undesirable self-pollination, out-crossing and mechanical admixtures. To overcome these problems the accepted method of postulating specific resistance genes based on comparing response type arrays (RTAs) of genetically homogeneous cultivars with RTAs of standard genotypes was substituted by analysing the frequency of response types to clusters of pathogen isolates in segregating F2 generations. This method combines a genetic and phytopathological approach for identifying resistance genes. To assess its applicability six hybrid cultivars were screened and from three to seven with a total of 14 resistance genes were found. Two genes were newly located at the Mla locus and their heritability determined. In addition, three unknown dominant genes were detected. This novel, comprehensive and efficient method to identifying resistance genes in hybrid cultivars can also be applied in other cereals and crops.
- MeSH
- Ascomycota patogenita MeSH
- ječmen (rod) genetika růst a vývoj mikrobiologie MeSH
- kvantitativní znak dědičný MeSH
- mapování chromozomů MeSH
- nemoci rostlin mikrobiologie MeSH
- odolnost vůči nemocem * MeSH
- regulace genové exprese u rostlin MeSH
- rostlinné proteiny genetika MeSH
- šlechtění rostlin MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- rostlinné proteiny MeSH
