Goatgrasses with U- and M-genomes are important sources of new alleles for wheat breeding to maintain yield and quality under extreme conditions. However, the introgression of beneficial traits from wild Aegilops species into wheat has been limited by poor knowledge of their genomes and scarcity of molecular tools. Here, we present the first linkage map of allotetraploid Aegilops biuncialis Vis., developed using 224 F2 individuals derived from a cross between MvGB382 and MvGB642 accessions. The map comprises 5663 DArTseq markers assigned to 15 linkage groups corresponding to 13 chromosomes. Chromosome 1Mb could not be constructed due to a lack of recombination caused by rearrangements in the MvGB382 accession. The genetic map spans 2518 cM with an average marker density of 2.79 cM. The skeleton map contains 920 segregating markers, divided between the Mb sub-genome (425 markers) and the Ub sub-genome (495 markers). Chromosomes of the Mb sub-genome, originating from Aegilops comosa Sm. in Sibth. et Sm., show well-preserved collinearity with Triticum aestivum L. chromosomes. In contrast, chromosomes of the Ub sub-genome, originating from Aegilops umbellulata Zhuk., exhibit a varying degree of collinearity, with 1Ub, 3Ub, and 5Ub retaining a substantial level of collinearity with Triticum aestivum, while 2Ub, 4Ub, 6Ub, and 7Ub show significant rearrangements. A quantitative trait locus affecting fertility was identified near the centromere on the long arm of chromosome 3Mb, explaining 23.5% of the variance. The genome structure of Aegilops biuncialis, highlighted by the genetic map, provides insights into the speciation within the species and will support alien gene transfer into wheat.

• MeSH
• Aegilops * genetika   MeSH
• chromozomy rostlin genetika   MeSH
• genetická vazba MeSH
• genetické markery MeSH
• genom rostlinný * MeSH
• mapování chromozomů MeSH
• pšenice * genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• genetické markery MeSH

Characterisation and genetic mapping of a key gene defining root morphology in bread wheat. Root morphology is central to plants for the efficient uptake up of soil water and mineral nutrients. Here we describe a conditional mutant of hexaploid wheat (Triticum aestivum L.) that when grown in soil with high Ca2+ develops a larger rhizosheath accompanied with shorter roots than the wild type. In wheat, rhizosheath size is a reliable surrogate for root hair length and this was verified in the mutant which possessed longer root hairs than the wild type when grown in high Ca2+ soil. We named the mutant Stumpy and showed it to be due to a single semi-dominant mutation. The short root phenotype at high Ca2+ was due to reduced cellular elongation which might also explain the long root hair phenotype. Analysis of root cell walls showed that the polysaccharide composition of Stumpy roots is remodelled when grown at non-permissive (high) Ca2+ concentrations. The mutation mapped to chromosome 7B and sequencing of the 7B chromosomes in both wild type and Stumpy identified a candidate gene underlying the Stumpy mutation. As part of the process to determine whether the candidate gene was causative, we identified wheat lines in a Cadenza TILLING population with large rhizosheaths but accompanied with normal root length. This finding illustrates the potential of manipulating the gene to disconnect root length from root hair length as a means of developing wheat lines with improved efficiency of nutrient and water uptake. The Stumpy mutant will be valuable for understanding the mechanisms that regulate root morphology in wheat.

• MeSH
• kořeny rostlin genetika   MeSH
• mapování chromozomů MeSH
• mutace MeSH
• pšenice * metabolismus   MeSH
• půda * MeSH
• voda metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• půda * MeSH
• voda MeSH

Semidwarfing genes have greatly increased wheat yields globally, yet the widely used gibberellin (GA)-insensitive genes Rht-B1b and Rht-D1b have disadvantages for seedling emergence. Use of the GA-sensitive semidwarfing gene Rht13 avoids this pleiotropic effect. Here, we show that Rht13 encodes a nucleotide-binding site/leucine-rich repeat (NB-LRR) gene. A point mutation in the semidwarf Rht-B13b allele autoactivates the NB-LRR gene and causes a height reduction comparable with Rht-B1b and Rht-D1b in diverse genetic backgrounds. The autoactive Rht-B13b allele leads to transcriptional up-regulation of pathogenesis-related genes including class III peroxidases associated with cell wall remodeling. Rht13 represents a new class of reduced height (Rht) gene, unlike other Rht genes, which encode components of the GA signaling or metabolic pathways. This discovery opens avenues to use autoactive NB-LRR genes as semidwarfing genes in a range of crop species, and to apply Rht13 in wheat breeding programs using a perfect genetic marker.

• Klíčová slova
• Triticum aestivum L. (wheat), autoactive NB-LRR, reduced-height (Rht) gene, semidwarfing gene,
• MeSH
• nanismus * MeSH
• nukleotidy metabolismus   MeSH
• pšenice * genetika   metabolismus   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• šlechtění rostlin MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• nukleotidy MeSH
• rostlinné proteiny MeSH

Wheat is one of the most important staple crops worldwide and also an excellent model species for crop evolution and polyploidization studies. The breakthrough of sequencing the bread wheat genome and progenitor genomes lays the foundation to decipher the complexity of wheat origin and evolutionary process as well as the genetic consequences of polyploidization. In this study, we sequenced 3286 BACs from chromosome 7DL of bread wheat cv. Chinese Spring and integrated the unmapped contigs from IWGSC v1 and available PacBio sequences to close gaps present in the 7DL assembly. In total, 8043 out of 12 825 gaps, representing 3 491 264 bp, were closed. We then used the improved assembly of 7DL to perform comparative genomic analysis of bread wheat (Ta7DL) and its D donor, Aegilops tauschii (At7DL), to identify domestication signatures. Results showed a strong syntenic relationship between Ta7DL and At7DL, although some small rearrangements were detected at the distal regions. A total of 53 genes appear to be lost genes during wheat polyploidization, with 23% (12 genes) as RGA (disease resistance gene analogue). Furthermore, 86 positively selected genes (PSGs) were identified, considered to be domestication-related candidates. Finally, overlapping of QTLs obtained from GWAS analysis and PSGs indicated that TraesCS7D02G321000 may be one of the domestication genes involved in grain morphology. This study provides comparative information on the sequence, structure and organization between bread wheat and Ae. tauschii from the perspective of the 7DL chromosome, which contribute to better understanding of the evolution of wheat, and supports wheat crop improvement.

• Klíčová slova
• 7DL chromosome arm, BAC by BAC, domestication, gene loss, physical mapping, wheat,
• MeSH
• Aegilops genetika   MeSH
• biologická evoluce * MeSH
• chromozomy rostlin genetika   MeSH
• genom rostlinný * MeSH
• lokus kvantitativního znaku MeSH
• pšenice genetika   MeSH
• srovnávací genomová hybridizace MeSH
• syntenie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Stem rust is an important disease of wheat that can be controlled using resistance genes. The gene SuSr-D1 identified in cultivar 'Canthatch' suppresses stem rust resistance. SuSr-D1 mutants are resistant to several races of stem rust that are virulent on wild-type plants. Here we identify SuSr-D1 by sequencing flow-sorted chromosomes, mutagenesis, and map-based cloning. The gene encodes Med15, a subunit of the Mediator Complex, a conserved protein complex in eukaryotes that regulates expression of protein-coding genes. Nonsense mutations in Med15b.D result in expression of stem rust resistance. Time-course RNAseq analysis show a significant reduction or complete loss of differential gene expression at 24 h post inoculation in med15b.D mutants, suggesting that transcriptional reprogramming at this time point is not required for immunity to stem rust. Suppression is a common phenomenon and this study provides novel insight into suppression of rust resistance in wheat.

• MeSH
• Basidiomycota patogenita   MeSH
• chromozomy rostlin genetika   MeSH
• duplikace genu MeSH
• exprese genu MeSH
• fenotyp MeSH
• imunita rostlin genetika   MeSH
• lipnicovité klasifikace   genetika   MeSH
• mapování chromozomů MeSH
• mediátorový komplex genetika   MeSH
• mutace MeSH
• nemoci rostlin genetika   imunologie   mikrobiologie   MeSH
• odolnost vůči nemocem genetika   MeSH
• pšenice genetika   imunologie   mikrobiologie   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné geny genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• mediátorový komplex MeSH

Leaf rust, caused by Puccinia triticina, threatens global wheat production due to the constant evolution of virulent pathotypes that defeat commercially deployed all stage-resistance (ASR) genes in modern cultivars. Hence, the deployment of combinations of adult plant resistance (APR) and ASR genes in new wheat cultivars is desirable. Adult plant resistance gene Lr49 was previously mapped on the long arm of chromosome 4B of cultivar VL404 and flanked by microsatellite markers barc163 (8.1 cM) and wmc349 (10.1 cM), neither of which was sufficiently closely linked for efficient marker assisted selection. This study used high-density SNP genotyping and flow sorted chromosome sequencing to fine-map the Lr49 locus as a starting point to develop a diagnostic marker for use in breeding and to clone this gene. Marker sunKASP_21 was mapped 0.4 cM proximal to Lr49, whereas a group of markers including sunKASP_24 were placed 0.6 cM distal to this gene. Testing of the linked markers on 75 Australian and 90 European cultivars with diverse genetic backgrounds showed that sunKASP_21 was most strongly associated with Lr49. Our results also show that the Lr49 genomic region contains structural variation relative to the reference stock Chinese Spring, possibly an inverted genomic duplication, which introduces a new set of challenges for the Lr49 cloning.

• Klíčová slova
• Infinium iSelect 90K SNP array, adult plant resistance, chromosome sorting, leaf rust, marker assisted breeding,
• Publikační typ
• časopisecké články MeSH

The capacity of the bread wheat (Triticum aestivum) genome to tolerate introgression from related genomes can be exploited for wheat improvement. A resistance to powdery mildew expressed by a derivative of the cross-bread wheat cv. Tähti × T. militinae (Tm) is known to be due to the incorporation of a Tm segment into the long arm of chromosome 4A. Here, a newly developed in silico method termed rearrangement identification and characterization (RICh) has been applied to characterize the introgression. A virtual gene order, assembled using the GenomeZipper approach, was obtained for the native copy of chromosome 4A; it incorporated 570 4A DArTseq markers to produce a zipper comprising 2132 loci. A comparison between the native and introgressed forms of the 4AL chromosome arm showed that the introgressed region is located at the distal part of the arm. The Tm segment, derived from chromosome 7G, harbours 131 homoeologs of the 357 genes present on the corresponding region of Chinese Spring 4AL. The estimated number of Tm genes transferred along with the disease resistance gene was 169. Characterizing the introgression's position, gene content and internal gene order should not only facilitate gene isolation, but may also be informative with respect to chromatin structure and behaviour studies.

• Klíčová slova
• GenomeZipper, alien introgression, chromosome rearrangement, chromosome translocation, comparative analysis, linkage drag,
• MeSH
• Ascomycota patogenita   MeSH
• chléb MeSH
• chromozomy rostlin genetika   metabolismus   MeSH
• DNA rostlinná genetika   MeSH
• genetické markery MeSH
• mapování chromozomů MeSH
• mikrosatelitní repetice MeSH
• nemoci rostlin genetika   mikrobiologie   MeSH
• odolnost vůči nemocem MeSH
• počítačová simulace MeSH
• pšenice genetika   mikrobiologie   MeSH
• rostlinné geny MeSH
• sekvence nukleotidů MeSH
• translokace genetická MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA rostlinná MeSH
• genetické markery MeSH

Bread wheat has a large and complex allohexaploid genome with low recombination level at chromosome centromeric and peri-centromeric regions. This significantly hampers ordering of markers, contigs of physical maps and sequence scaffolds and impedes obtaining of high-quality reference genome sequence. Here we report on the construction of high-density and high-resolution radiation hybrid (RH) map of chromosome 4A supported by high-density chromosome deletion map. A total of 119 endosperm-based RH lines of two RH panels and 15 chromosome deletion bin lines were genotyped with 90K iSelect single nucleotide polymorphism (SNP) array. A total of 2316 and 2695 markers were successfully mapped to the 4A RH and deletion maps, respectively. The chromosome deletion map was ordered in 19 bins and allowed precise identification of centromeric region and verification of the RH panel reliability. The 4A-specific RH map comprises 1080 mapping bins and spans 6550.9 cR with a resolution of 0.13 Mb/cR. Significantly higher mapping resolution in the centromeric region was observed as compared to recombination maps. Relatively even distribution of deletion frequency along the chromosome in the RH panel was observed and putative functional centromere was delimited within a region characterized by two SNP markers.

• Klíčová slova
• SNP iSelect array, Triticum aestivum, chromosome deletion bin map, endosperm radiation hybrid panel, radiation hybrid map, wheat chromosome 4A,
• Publikační typ
• časopisecké články MeSH