Powdery mildew, caused by Blumeria graminis f. sp. tritici, is one of the most important wheat diseases in the world. In this study, a single dominant powdery mildew resistance gene MlIW172 was identified in the IW172 wild emmer accession and mapped to the distal region of chromosome arm 7AL (bin7AL-16-0.86-0.90) via molecular marker analysis. MlIW172 was closely linked with the RFLP probe Xpsr680-derived STS marker Xmag2185 and the EST markers BE405531 and BE637476. This suggested that MlIW172 might be allelic to the Pm1 locus or a new locus closely linked to Pm1. By screening genomic BAC library of durum wheat cv. Langdon and 7AL-specific BAC library of hexaploid wheat cv. Chinese Spring, and after analyzing genome scaffolds of Triticum urartu containing the marker sequences, additional markers were developed to construct a fine genetic linkage map on the MlIW172 locus region and to delineate the resistance gene within a 0.48 cM interval. Comparative genetics analyses using ESTs and RFLP probe sequences flanking the MlIW172 region against other grass species revealed a general co-linearity in this region with the orthologous genomic regions of rice chromosome 6, Brachypodium chromosome 1, and sorghum chromosome 10. However, orthologous resistance gene-like RGA sequences were only present in wheat and Brachypodium. The BAC contigs and sequence scaffolds that we have developed provide a framework for the physical mapping and map-based cloning of MlIW172.
The novel wheat powdery mildew and stripe rust resistance genes Pm5V/Yr5V are introgressed from Dasypyrum villosum and fine mapped to a narrowed region in 5VS, and their effects on yield-related traits were characterized. The powdery mildew and stripe rust seriously threaten wheat production worldwide. Dasypyrum villosum (2n = 2x = 14, VV), a relative of wheat, is a valuable resource of resistance genes for wheat improvement. Here, we describe a platform for rapid introgression of the resistance genes from D. villosum into the wheat D genome. A complete set of new wheat-D. villosum V (D) disomic substitution lines and 11 D/V Robertsonian translocation lines are developed and characterized by molecular cytogenetic method. A new T5DL·5V#5S line NAU1908 shows resistance to both powdery mildew and stripe rust, and the resistances associated with 5VS are confirmed to be conferred by seedling resistance gene Pm5V and adult-plant resistance gene Yr5V, respectively. We flow-sort chromosome arm 5VS and sequence it using the Illumina NovaSeq 6000 system that allows us to generate 5VS-specific markers for genetic mapping of Pm5V/Yr5V. Fine mapping shows that Pm5V and Yr5V are closely linked and the location is narrowed to an approximately 0.9 Mb region referencing the sequence of Chinese Spring 5DS. In this region, a NLR gene in scaffold 24,874 of 5VS orthologous to TraesCS5D02G044300 is the most likely candidate gene for Pm5V. Soft- and hard-grained T5DL·5V#5S introgressions confer resistance to both powdery mildew and stripe rust in diverse wheat genetic backgrounds without yield penalty. Meanwhile, significant decrease in plant height and increase in yield were observed in NIL-5DL·5V#5S compared with that in NIL-5DL·5DS. These results indicate that Pm5V/Yr5V lines might have the potential value to facilitate wheat breeding for disease resistance.
- MeSH
- Basidiomycota * MeSH
- Poaceae genetics MeSH
- Plant Diseases genetics MeSH
- Disease Resistance genetics MeSH
- Triticum * genetics MeSH
- Plant Breeding MeSH
- Publication type
- Journal Article MeSH
Human activities including those in crop gene banks are subject to errors, especially during seed multiplication and maintenance of seed germination. Therefore, the most serious problem of gene banks is authenticity of the accessions and their genotypic purity. There are many methods for determining the identity of varieties, but comparisons between current data and past records are not easy since the latter are often missing. Breeding barley resistant to powdery mildew caused by Blumeria graminis f. sp. hordei (Bgh) was traditionally based on incorporating major genes into new varieties and the results have been published. Our goal was to identify resistance genes to powdery mildew in accessions of the Czech spring barley core collection and compare these data with earlier information to establish the authenticity of the accessions. Two hundred and twenty-three accessions of the collection including 665 single plant progenies were tested. Sixty-four selected reference isolates of Bgh representing the world diversity of the pathogen were used for resistance tests. Twenty-two known resistance genes were postulated either separately or in combinations. In the collection, 151 homogeneous accessions were found, but the resistances of nine of them were inconsistent with published data and in 12 accessions their authenticity is doubtful. The remaining 72 accessions were heterogeneous and comprised 176 resistance genotypes, 54 of which were probably mechanical admixtures of other varieties. There are several pathogens of cereals, e.g. rusts and mildews, against which many resistance genes in host crops have also been exploited. Knowledge of these resistances can assist in maintaining pure and genuine stocks in gene banks. Seed purity and the authenticity of accessions can subsequently be checked with more advanced methods.
- Publication type
- Meeting Abstract MeSH
Spot blotch (SB) caused by Bipolaris sorokiniana and powdery mildew (PM) caused by Blumeria graminis f. sp. hordei are two important diseases of barley. To map genetic loci controlling susceptibility and resistance to these diseases, a mapping population consisting of 138 recombinant inbred lines (RILs) was developed from the cross between Bowman and ND5883. A genetic map was constructed for the population with 852 unique single nucleotide polymorphism markers generated by sequencing-based genotyping. Bowman and ND5883 showed distinct infection responses at the seedling stage to two isolates (ND90Pr and ND85F) of Bipolaris sorokiniana and one isolate (Race I) of Blumeria graminis f. sp. hordei. Genetic analysis of the RILs revealed that one major gene (Scs6) controls susceptibility to Bipolaris sorokiniana isolate ND90Pr, and another major gene (Mla8) confers resistance to Blumeria graminis f. sp. hordei isolate Race I, respectively. Scs6 was mapped on chromosome 1H of Bowman, as previously reported. Mla8 was also mapped to the short arm of 1H, which was tightly linked but not allelic to the Rcs6/Scs6 locus. Quantitative trait locus (QTL) analysis identified two QTLs, QSbs-1H-P1 and QSbs-7H-P1, responsible for susceptibility to spot blotch caused by Bipolaris sorokiniana isolate ND85F in ND5883, which are located on chromosome 1H and 7H, respectively. QSbs-7H-P1 was mapped to the same region as Rcs5, whereas QSbs-1H-P1 may represent a novel allele conferring seedling stage susceptibility to isolate ND85F. Identification and molecular mapping of the loci for SB susceptibility and PM resistance will facilitate development of barley cultivars with resistance to the diseases.
- MeSH
- Ascomycota * MeSH
- Genotype MeSH
- Hordeum * MeSH
- Chromosome Mapping MeSH
- Plant Diseases MeSH
- Disease Resistance MeSH
- Publication type
- Journal Article MeSH
A segment of Triticum militinae chromosome 7G harbors a gene(s) conferring powdery mildew resistance which is effective at both the seedling and the adult plant stages when transferred into bread wheat (T. aestivum). The introgressed segment replaces a piece of wheat chromosome arm 4AL. An analysis of segregating materials generated to positionally clone the gene highlighted that in a plant heterozygous for the introgression segment, only limited recombination occurs between the introgressed region and bread wheat 4A. Nevertheless, 75 genetic markers were successfully placed within the region, thereby confining the gene to a 0.012 cM window along the 4AL arm. In a background lacking the Ph1 locus, the localized rate of recombination was raised 33-fold, enabling the reduction in the length of the region containing the resistance gene to a 480 kbp stretch harboring 12 predicted genes. The substituted segment in the reference sequence of bread wheat cv. Chinese Spring is longer (640 kbp) and harbors 16 genes. A comparison of the segments' sequences revealed a high degree of divergence with respect to both their gene content and nucleotide sequence. Of the 12 T. militinae genes, only four have a homolog in cv. Chinese Spring. Possible candidate genes for the resistance have been identified based on function predicted from their sequence.
- MeSH
- Molecular Sequence Annotation MeSH
- Ascomycota physiology MeSH
- Bread MeSH
- Chromosomes, Plant genetics MeSH
- Genetic Variation * MeSH
- Genetic Loci * MeSH
- Cloning, Molecular MeSH
- Chromosome Mapping MeSH
- Plant Diseases genetics immunology microbiology MeSH
- Disease Resistance genetics MeSH
- Triticum genetics immunology microbiology MeSH
- Genes, Plant * MeSH
- Publication type
- Journal Article MeSH
- Publication type
- Meeting Abstract MeSH
