Nejvíce citovaný článek - PubMed ID 30532221
Identification of barley powdery mildew resistances in gene bank accessions and the use of gene diversity for verifying seed purity and authenticity
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
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.
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, 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
Powdery mildew caused by the airborne ascomycete fungus Blumeria graminis f. sp. hordei (Bgh) is one of most common diseases of barley (Hordeum vulgare). This, as with many other plant pathogens, can be efficiently controlled by inexpensive and environmentally-friendly genetic resistance. General requirements for resistance to the pathogens are effectiveness and durability. Resistance of barley to Bgh has been studied intensively, and this review describes recent research and summarizes the specific resistance genes found in barley varieties since the last conspectus. Bgh is extraordinarily adaptable, and some commonly recommended strategies for using genetic resistance, including pyramiding of specific genes, may not be effective because they can only contribute to a limited extent to obtain sufficient resistance durability of widely-grown cultivars. In spring barley, breeding the nonspecific mlo gene is a valuable source of durable resistance. Pyramiding of nonspecific quantitative resistance genes or using introgressions derived from bulbous barley (Hordeum bulbosum) are promising ways for breeding future winter barley cultivars. The utilization of a wide spectrum of nonhost resistances can also be adopted once practical methods have been developed.
- Klíčová slova
- Blumeria graminis f. sp. hordei, Hordeum vulgare, barley, durability of resistance, powdery mildew, specific resistance,
- MeSH
- Ascomycota genetika patogenita MeSH
- fenotyp MeSH
- interakce hostitele a patogenu * MeSH
- ječmen (rod) genetika mikrobiologie MeSH
- nemoci rostlin genetika mikrobiologie MeSH
- odolnost vůči nemocem genetika MeSH
- rostlinné proteiny genetika MeSH
- šlechtění rostlin * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- rostlinné proteiny MeSH
