Regenerative Metaplastic Clones in COPD Lung Drive Inflammation and Fibrosis.

Chronic obstructive pulmonary disease (COPD) is a progressive condition of chronic bronchitis, small airway obstruction, and emphysema that represents a leading cause of death worldwide. While inflammation, fibrosis, mucus hypersecretion, and metaplastic epithelial lesions are hallmarks of this disease, their origins and dependent relationships remain unclear. Here we apply single-cell cloning technologies to lung tissue of patients with and without COPD. Unlike control lungs, which were dominated by normal distal airway progenitor cells, COPD lungs were inundated by three variant progenitors epigenetically committed to distinct metaplastic lesions. When transplanted to immunodeficient mice, these variant clones induced pathology akin to the mucous and squamous metaplasia, neutrophilic inflammation, and fibrosis seen in COPD. Remarkably, similar variants pre-exist as minor constituents of control and fetal lung and conceivably act in normal processes of immune surveillance. However, these same variants likely catalyze the pathologic and progressive features of COPD when expanded to high numbers.

Fine mapping of powdery mildew resistance gene MlWE74 derived from wild emmer wheat (Triticum turgidum ssp. dicoccoides) in an NBS-LRR gene cluster.

KEY MESSAGE: Powdery mildew resistance gene MlWE74, originated from wild emmer wheat accession G-748-M, was mapped in an NBS-LRR gene cluster of chromosome 2BS. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a globally devastating disease. Wild emmer wheat (Triticum turgidum var. dicoccoides) is a valuable genetic resource for improving disease resistance in common wheat. A powdery mildew resistance gene was transferred to hexaploid wheat line WE74 from wild emmer accession G-748-M. Genetic analysis revealed that the powdery mildew resistance in WE74 is controlled by a single dominant gene, herein temporarily designated MlWE74. Bulked segregant analysis (BSA) and molecular mapping delimited MlWE74 to the terminal region of chromosome 2BS flanking by markers WGGBD412 and WGGBH346 within a genetic interval of 0.25 cM and corresponding to 799.9 kb genomic region in the Zavitan reference sequence. Sequence annotation revealed two phosphoglycerate mutase-like genes, an alpha/beta-hydrolases gene, and five NBS-LRR disease resistance genes that could serve as candidates for map-based cloning of MlWE74. The geographical location analysis indicated that MlWE74 is mainly distributed in Rosh Pinna and Amirim regions, in the northern part of Israel, where environmental conditions are favorable to the occurrence of powdery mildew. Moreover, the co-segregated marker WGGBD425 is helpful in marker-assisted transfer of MlWE74 into elite cultivars.

Identifying features of source and message that influence the retweeting of health information on social media during the COVID-19 pandemic.

BACKGROUND: Social media has become an essential tool to implement risk communication, giving health information could gain more exposure by retweeting during the COVID-19 pandemic. METHODS: Content analysis was conducted to scrutinize the official (national and provincial) public health agencies' Weibo posts (n = 4396) to identify features of information sources and message features (structure, style content). The Zero-Inflated Negative Binomial (ZINB) model was adopted to analyze the association between these features and the frequency of the retweeted messages. RESULTS: Results indicated that features of source and health information, such as structure, style, and content, were correlated to retweeting. The results of IRR further suggested that compared to provincial accounts, messages from national health authorities' accounts gained more retweeting. Regarding the information features, messages with hashtags#, picture, video have been retweeted more often than messages without any of these features respectively, while messages with hyperlinks received fewer retweets than messages without hyperlinks. In terms of the information structure, messages with the sentiment (!) have been retweeted more frequently than messages without sentiment. Concerning content, messages containing severity, reassurance, efficacy, and action frame have been retweeted with higher frequency, while messages with uncertainty frames have been retweeted less often. CONCLUSIONS: Health organizations and medical professionals should pay close attention to the features of health information sources, structures, style, and content to satisfy the public's information needs and preferences to promote the public's health engagement. Designing suitable information systems and promoting health communication strategies during different pandemic stages may improve public awareness of the COVID-19, alleviate negative emotions, and promote preventive measures to curb the spread of the virus.

Molecular Characterization of All-Stage and Adult-Plant Resistance Loci Against Powdery Mildew in Winter Wheat Cultivar Liangxing 99 Using BSR-Seq Technology.

Winter wheat cultivar Liangxing 99, which carries gene Pm52, is resistant to powdery mildew at both seedling and adult-plant stages. An F2:6 recombinant inbred line population from cross Liangxing 99 × Zhongzuo 9504 was phenotyped with Blumeria graminis f. sp. tritici isolate Bgt27 at the adult-plant stage in four field tests and the seedling stage in a greenhouse test. The analysis of bulk segregant RNA sequencing (BSR-Seq) identified a single-nucleotide polymorphism-enriched locus, Qaprpm.caas.2B, on chromosome 2BL in the same genomic interval of Pm52 associated with the all-stage resistance (ASR) and Qaprpm.caas.7A on chromosome 7AL associated with the adult-plant resistance (APR) against the disease. Qaprpm.caas.2B was detected in a 1.3 cM genetic interval between markers Xicscl726 and XicsK128 in which Pm52 was placed with a range of logarithm of odds (LOD) values from 28.1 to 34.6, and the phenotype variations explained in terms of maximum disease severity (MDS) ranged from 45 to 52%. The LOD peak of Qaprpm.caas.7A was localized in a 4.6 cM interval between markers XicsK7A8 and XicsK7A26 and explained the phenotypic variation of MDS ranging from 13 to 16%. The results of this study confirmed Pm52 for ASR and identified Qaprpm.caas.7A for APR to powdery mildew in Liangxing 99.

A CNL protein in wild emmer wheat confers powdery mildew resistance.

Powdery mildew, a fungal disease caused by Blumeria graminis f. sp. tritici (Bgt), has a serious impact on wheat production. Loss of resistance in cultivars prompts a continuing search for new sources of resistance. Wild emmer wheat (Triticum turgidum ssp. dicoccoides, WEW), the progenitor of both modern tetraploid and hexaploid wheats, harbors many powdery mildew resistance genes. We report here the positional cloning and functional characterization of Pm41, a powdery mildew resistance gene derived from WEW, which encodes a coiled-coil, nucleotide-binding site and leucine-rich repeat protein (CNL). Mutagenesis and stable genetic transformation confirmed the function of Pm41 against Bgt infection in wheat. We demonstrated that Pm41 was present at a very low frequency (1.81%) only in southern WEW populations. It was absent in other WEW populations, domesticated emmer, durum, and common wheat, suggesting that the ancestral Pm41 was restricted to its place of origin and was not incorporated into domesticated wheat. Our findings emphasize the importance of conservation and exploitation of the primary WEW gene pool, as a valuable resource for discovery of resistance genes for improvement of modern wheat cultivars.

A rare single nucleotide variant in Pm5e confers powdery mildew resistance in common wheat.

Powdery mildew poses severe threats to wheat production. The most sustainable way to control this disease is through planting resistant cultivars. We report the map-based cloning of the powdery mildew resistance allele Pm5e from a Chinese wheat landrace. We applied a two-step bulked segregant RNA sequencing (BSR-Seq) approach in developing tightly linked or co-segregating markers to Pm5e. The first BSR-Seq used phenotypically contrasting bulks of recombinant inbred lines (RILs) to identify Pm5e-linked markers. The second BSR-Seq utilized bulks of genetic recombinants screened from a fine-mapping population to precisely quantify the associated genomic variation in the mapping interval, and identified the Pm5e candidate genes. The function of Pm5e was validated by transgenic assay, loss-of-function mutants and haplotype association analysis. Pm5e encodes a nucleotide-binding domain leucine-rich-repeat-containing (NLR) protein. A rare nonsynonymous single nucleotide variant (SNV) within the C-terminal leucine rich repeat (LRR) domain is responsible for the gain of powdery mildew resistance function of Pm5e, an allele endemic to wheat landraces of Shaanxi province of China. Results from this study demonstrate the value of landraces in discovering useful genes for modern wheat breeding. The key SNV associated with powdery mildew resistance will be useful for marker-assisted selection of Pm5e in wheat breeding programs.

Correction to: Alternative splicing of a barley gene results in an excess­tillering and semi­dwarf mutant.

In the original publication of this article, the acknowledgement section has been missed to publish. Now the same has been provided in this correction.

Alternative splicing of a barley gene results in an excess-tillering and semi-dwarf mutant.

KEY MESSAGE: An excess-tillering semi-dwarf gene Hvhtd was identified from an EMS-induced mutant in barley and alternative splicing results in excess-tillering semi-dwarf traits. Tillering and plant height are important traits determining plant architecture and grain production in cereal crops. This study identified an excess-tillering semi-dwarf mutant (htd) from an EMS-treated barley population. Genetic analysis of the F1, F2, and F2:3 populations showed that a single recessive gene controlled the excess-tillering semi-dwarf in htd. Using BSR-Seq and gene mapping, the Hvhtd gene was delimited within a 1.8 Mb interval on chromosome 2HL. Alignment of the RNA-Seq data with the functional genes in the interval identified a gene HORVU2Hr1G098820 with alternative splicing between exon2 and exon3 in the mutant, due to a G to A single-nucleotide substitution at the exon and intron junction. An independent mutant with a similar phenotype confirmed the result, with alternative splicing between exon3 and exon4. In both cases, the alternative splicing resulted in a non-functional protein. And the gene HORVU2Hr1G098820 encodes a trypsin family protein and may be involved in the IAA signaling pathway and differs from the mechanism of Green Revolution genes in the gibberellic acid metabolic pathway.

Identification and fine mapping of spot blotch (Bipolaris sorokiniana) resistance gene Sb4 in wheat.

KEY MESSAGE: A new spot blotch (Bipolaris sorokiniana) resistance gene Sb4 was mapped in a genomic interval of 1.34 Mb on wheat chromosome 4BL. Spot blotch, caused by Bipolaris sorokiniana, has emerged as a serious concern for cultivation of wheat in warmer and humid regions of the world, which results in substantial yield losses and descends with quality. In this study, we identified and mapped a spot blotch resistance gene, designated as Sb4, against B. sorokiniana in wheat. Bulked segregant RNA-Seq (BSR-Seq) analysis and single-nucleotide polymorphism mapping showed that Sb4 is located on the long arm of chromosome 4B. A genetic linkage map of Sb4 was constructed using an F4 mapping population developed from the cross between 'GY17' and 'Zhongyu1211,' and Sb4 was delimited in a 7.14-cM genetic region on 4BL between markers B6811 and B6901. Using the Chinese Spring reference sequences of chromosome arm 4BL, 13 new polymorphic markers were developed. Finally, Sb4 was mapped in a 1.19-cM genetic interval corresponding to a 1.34-Mb physical genomic region of Chinese Spring chromosome 4BL containing 21 predicted genes. This study provides a foundational step for further cloning of Sb4 using a map-based approach.

Resistance to Heterodera filipjevi and H. avenae in Winter Wheat is Conferred by Different QTL.

The coexistence of cereal cyst nematode (CCN) species Heterodera avenae and H. filipjevi, often involving multiple pathotypes, is a limiting factor for wheat production in China. Some of the known genes for resistance to CCN are not effective against both nematode species, hence complicating breeding efforts to develop CCN-resistant wheat cultivars. Here, we demonstrate that the CCN resistance in wheat cultivar Madsen to both Heterodera spp. is controlled by different genetic loci, both of which originated from Aegilops ventricosa. A new quantitative trait locus (QTL), QCre-ma7D, was identified and localized in a 3.77-Mb genomic region on chromosome arm 7DL, which confers resistance to H. filipjevi. QCre-ma2A on chromosome arm 2AS corresponds to CCN resistance gene Cre5 and confers resistance to H. avenae. This QTL is a new locus on chromosome arm 7DL and is designated Cre9. Three Kompetitive allele-specific PCR markers (BS00150072, BS00021745, and BS00154302) were developed for molecular marker-assisted selection of Cre9 and locally adapted wheat lines with resistance to both nematode species were developed. QCre-ma2A on chromosome arm 2AS corresponds to CCN resistance gene Cre5 and confers resistance to H. avenae. The identification of different loci underlying resistance to H. filipjevi and H. avenae and the development of adapted resistant entries will facilitate breeding of wheat cultivars that are resistant to these devastating nematodes in China.

Identification of a Recessive Gene PmQ Conferring Resistance to Powdery Mildew in Wheat Landrace Qingxinmai Using BSR-Seq Analysis.

Wheat powdery mildew is caused by Blumeria graminis f. sp. tritici (Bgt), a biotrophic fungal species. It is very important to mine new powdery mildew (Pm) resistance genes for developing resistant wheat cultivars to reduce the deleterious effects of the disease. This study was carried out to characterize the Pm gene in Qingxinmai, a winter wheat landrace from Xinjiang, China. Qingxinmai is resistant to many Bgt isolates collected from different wheat fields in China. F1, F2, and F2:3 generations of the cross between Qingxinmai and powdery mildew susceptible line 041133 were developed. It was confirmed that a single recessive gene, PmQ, conferred the seedling resistance to a Bgt isolate in Qingxinmai. Bulked segregant analysis-RNA-Seq (BSR-Seq) was performed on the bulked homozygous resistant and susceptible F2:3 families, which detected 57 single nucleotide polymorphism (SNP) variants that were enriched in a 40 Mb genomic interval on chromosome arm 2BL. Based on the flanking sequences of the candidate SNPs extracted from the Chinese Spring reference genome, 485 simple sequence repeat (SSR) markers were designed. Six polymorphic SSR markers, together with nine markers that were anchored on chromosome arm 2BL, were used to construct a genetic linkage map for PmQ. This gene was placed in a 1.4 cM genetic interval between markers Xicsq405 and WGGBH913 corresponding to 4.9 Mb physical region in the Chinese Spring reference genome. PmQ differed from most of the other Pm genes identified on chromosome arm 2BL based on its position and/or origin. However, this gene and Pm63 from an Iranian common wheat landrace were located in a similar genomic region, so they may be allelic.

Development of SNP, KASP, and SSR Markers by BSR-Seq Technology for Saturation of Genetic Linkage Map and Efficient Detection of Wheat Powdery Mildew Resistance Gene Pm61.

The gene Pm61 that confers powdery mildew resistance has been previously identified on chromosome arm 4AL in Chinese wheat landrace Xuxusanyuehuang (XXSYH). To facilitate the use of Pm61 in breeding practices, the bulked segregant analysis-RNA-Seq (BSR-Seq) analysis, in combination with the information on the Chinese Spring reference genome sequence, was performed in the F2:3 mapping population of XXSYH × Zhongzuo 9504. Two single nucleotide polymorphism (SNP), two Kompetitive Allele Specific PCR (KASP), and six simple sequence repeat (SSR) markers, together with previously identified polymorphic markers, saturated the genetic linkage map for Pm61, especially in the proximal side of the target gene that was short of gene-linked markers. In the newly established genetic linkage map, Pm61 was located in a 0.71 cM genetic interval and can be detected in a high throughput scale by the KASP markers Xicsk8 and Xicsk13 or by the standard PCR-based markers Xicscx497 and Xicsx538. The newly saturated genetic linkage map will be useful in molecular marker assisted-selection of Pm61 in breeding for disease resistant cultivar and in its map-based cloning.

Mapping stripe rust resistance gene YrZH22 in Chinese wheat cultivar Zhoumai 22 by bulked segregant RNA-Seq (BSR-Seq) and comparative genomics analyses.

KEY MESSAGE: A stripe rust resistance gene YrZH22 was mapped by combined BSR-Seq and comparative genomics analyses to a 5.92 centimorgan (cM) genetic interval spanning a 4 Mb physical genomic region on wheat chromosome 4BL1. Stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most destructive diseases of wheat and severely threatens wheat production worldwide. The widely grown Chinese wheat cultivar Zhoumai 22 is highly resistant to the current prevailing PST race CYR34 (V26). Genetic analysis of F5:6 and F6:7 recombinant inbred line (RIL) populations indicated that adult-plant stripe rust resistance in Zhoumai 22 is controlled by a single gene, temporarily designated YrZH22. By applying bulked segregant RNA-Seq (BSR-Seq), 7 SNP markers were developed and SNP mapping showed that YrZH22 is located between markers WGGB105 and WGGB112 on chromosome arm 4BL. The corresponding genomic regions of the Chinese Spring 4BL genome assembly and physical map of Aegilops tauschii 4DL were selected for comparative genomics analyses to develop nine new polymorphic markers that were used to construct a high-resolution genetic linkage map of YrZH22. YrZH22 was delimited in a 5.92 cM genetic interval between markers WGGB133 and WGGB146, corresponding to 4.1 Mb genomic interval in Chinese Spring 4BL and a 2.2 Mb orthologous genomic region in Ae. tauschii 4DL. The genetic linkage map of YrZH22 will be valuable for fine mapping and positional cloning of YrZH22, and can be used for marker-assisted selection in wheat breeding.

Long read and single molecule DNA sequencing simplifies genome assembly and TAL effector gene analysis of Xanthomonas translucens.

BACKGROUND: The species Xanthomonas translucens encompasses a complex of bacterial strains that cause diseases and yield loss on grass species including important cereal crops. Three pathovars, X. translucens pv. undulosa, X. translucens pv. translucens and X. translucens pv.cerealis, have been described as pathogens of wheat, barley, and oats. However, no complete genome sequence for a strain of this complex is currently available. RESULTS: A complete genome sequence of X. translucens pv. undulosa strain XT4699 was obtained by using PacBio long read, single molecule, real time (SMRT) DNA sequences and Illumina sequences. Draft genome sequences of nineteen additional X. translucens strains, which were collected from wheat or barley in different regions and at different times, were generated by Illumina sequencing. Phylogenetic relationships among different Xanthomonas strains indicates that X. translucens are members of a distinct clade from so-called group 2 xanthomonads and three pathovars of this species, undulosa, translucens and cerealis, represent distinct subclades in the group 1 clade. Knockout mutation of type III secretion system of XT4699 eliminated the ability to cause water-soaking symptoms on wheat and barley and resulted in a reduction in populations on wheat in comparison to the wild type strain. Sequence comparison of X. translucens strains revealed the genetic variation on type III effector repertories among different pathovars or within one pathovar. The full genome sequence of XT4699 reveals the presence of eight members of the Transcription-Activator Like (TAL) effector genes, which are phylogenetically distant from previous known TAL effector genes of group 2 xanthomonads. Microarray and qRT-PCR analyses revealed TAL effector-specific wheat gene expression modulation. CONCLUSIONS: PacBio long read sequencing facilitates the assembly of Xanthomonas genomes and the multiple TAL effector genes, which are difficult to assemble from short read platforms. The complete genome sequence of X. translucens pv. undulosa strain XT4699 and draft genome sequences of nineteen additional X. translucens strains provides a resource for further genetic analyses of pathogenic diversity and host range of the X. translucens species complex. TAL effectors of XT4699 strain play roles in modulating wheat host gene expressions.

Fine genetic mapping of spot blotch resistance gene Sb3 in wheat (Triticum aestivum).

KEY MESSAGE: Spot blotch disease resistance gene Sb3 was mapped to a 0.15 centimorgan (cM) genetic interval spanning a 602 kb physical genomic region on chromosome 3BS. Wheat spot blotch disease, caused by B. sorokiniana, is a devastating disease that can cause severe yield losses. Although inoculum levels can be reduced by planting disease-free seed, treatment of plants with fungicides and crop rotation, genetic resistance is likely to be a robust, economical and environmentally friendly tool in the control of spot blotch. The winter wheat line 621-7-1 confers immune resistance against B. sorokiniana. Genetic analysis indicates that the spot blotch resistance of 621-7-1 is controlled by a single dominant gene, provisionally designated Sb3. Bulked segregant analysis (BSA) and simple sequence repeat (SSR) mapping showed that Sb3 is located on chromosome arm 3BS linked with markers Xbarc133 and Xbarc147. Seven and twelve new polymorphic markers were developed from the Chinese Spring 3BS shotgun survey sequence contigs and 3BS reference sequences, respectively. Finally, Sb3 was mapped in a 0.15 cM genetic interval spanning a 602 kb physical genomic region of Chinese Spring chromosome 3BS. The genetic and physical maps of Sb3 provide a framework for map-based cloning and marker-assisted selection (MAS) of the spot blotch resistance.

Comparative fine mapping of the Wax 1 (W1) locus in hexaploid wheat.

KEY MESSAGE: By applying comparative genomics analyses, a high-density genetic linkage map of the Wax 1 ( W1 ) locus was constructed as a framework for map-based cloning. Glaucousness is described as the scattering effect of visible light from wax deposited on the cuticle of plant aerial organs. In wheat, the wax on leaves and stems is mainly controlled by two sets of genes: glaucousness loci (W1 and W2) and non-glaucousness loci (Iw1 and Iw2). Bulked segregant analysis (BSA) and simple sequence repeat (SSR) mapping showed that Wax1 (W1) is located on chromosome arm 2BS between markers Xgwm210 and Xbarc35. By applying comparative genomics analyses, colinearity genomic regions of the W1 locus on wheat 2BS were identified in Brachypodium distachyon chromosome 5, rice chromosome 4 and sorghum chromosome 6, respectively. Four STS markers were developed using the Triticum aestivum cv. Chinese Spring 454 contig sequences and the International Wheat Genome Sequencing Consortium (IWGSC) survey sequences. W1 was mapped into a 0.93 cM genetic interval flanked by markers XWGGC3197 and XWGGC2484, which has synteny with genomic regions of 56.5 kb in Brachypodium, 390 kb in rice and 31.8 kb in sorghum. The fine genetic map can serve as a framework for chromosome landing, physical mapping and map-based cloning of the W1 in wheat.

Genetic and physical mapping of powdery mildew resistance gene MlHLT in Chinese wheat landrace Hulutou.

KEY MESSAGE: A powdery mildew resistance gene MlHLT derived from a Chinese wheat landrace maps within a 3.6 centimorgan (cM) genetic interval spanning a 13.4 megabase (Mb) physical genomic region on chromosome 1DS. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt) is a devastating disease that can cause severe yield losses. Chinese wheat landrace Hulutou confers nearly immune resistance against prevailing Bgt isolate E09 in Beijing. Genetic analysis indicate that the powdery mildew resistance of Hulutou is controlled by a single dominant gene, provisionally designated MlHLT. Bulked segregant analysis(BSA) and simple sequence repeat (SSR) mapping showed that MlHLT is located on chromosome arm 1DS between markers Xgwm337 and Xcfd83/Xcfd72. By applying comparative genomics analysis, collinearity genomic regions of the MlHLT locus on Aegilops tauschii chromosome 1DS were identified in Brachypodium distachyon chromosome 2, rice chromosome 5 and sorghum chromosome 9, respectively. Three new polymorphic markers were developed using the draft genome sequences and the extended single nucleotide polymorphism (SNP) marker sequences of Ae. tauschii accession AL8/78, as well as the Triticum aestivum cv. Chinese Spring 454 contig sequences and the International Wheat Genome Sequencing Consortium (IWGSC) survey sequences. MlHLT mapped into a 3.6 cM genetic interval spanning 13.4 Mb physical genomic region containing seven contigs (ctg220, ctg4623, ctg1063, ctg5929, ctg3163, ctg699 and ctg1065) on 1DS that has synteny with a 369.8 kb genomic region in Brachypodium, a 380.8 kb genomic region in rice and a 298.4 kb genomic region in sorghum. The genetic and physical maps of MlHLT provide framework for map-based cloning and marker-assisted selection (MAS) of the powdery mildew resistance gene MlHLT in Hulutou.

Dynamic evolution of resistance gene analogs in the orthologous genomic regions of powdery mildew resistance gene MlIW170 in Triticum dicoccoides and Aegilops tauschii.

KEY MESSAGE: Rapid evolution of powdery mildew resistance gene MlIW170 orthologous genomic regions in wheat subgenomes. Wheat is one of the most important staple grain crops in the world and also an excellent model for plant ploidy evolution research with different ploidy levels from diploid to hexaploid. Powdery mildew disease caused by Blumeria graminis f.sp. tritici can result in significant loss in both grain yield and quality in wheat. In this study, the wheat powdery mildew resistance gene MlIW170 locus located at the Triticum dicoccoides chromosome 2B short arm was further characterized by constructing and sequencing a BAC-based physical map contig covering a 0.3 cM genetic distance region (880 kb) and developing additional markers to delineate the resistance gene within a 0.16 cM genetic interval (372 kb). Comparative analyses of the T. dicoccoides 2BS region with the orthologous Aegilops tauschii 2DS region showed great gene colinearity, including the structure organization of both types of RGA1/2-like and RPS2-like resistance genes. Comparative analyses with the orthologous regions from Brachypodium and rice genomes revealed considerable dynamic evolutionary changes that have re-shaped this MlIW170 region in the wheat genome, resulting in a high number of non-syntenic genes including resistance-related genes. This result might reflect the rapid evolution in R-gene regions. Phylogenetic analysis on these resistance-related gene sequences indicated the duplication of these genes in the MlIW170 region, occurred before the separation of the wheat B and D genomes.

Comparative genetic mapping and genomic region collinearity analysis of the powdery mildew resistance gene Pm41.

KEY MESSAGE: By applying comparative genomics analyses, a high-density genetic linkage map narrowed the powdery mildew resistance gene Pm41 originating from wild emmer in a sub-centimorgan genetic interval. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici, results in large yield losses worldwide. A high-density genetic linkage map of the powdery mildew resistance gene Pm41, originating from wild emmer (Triticum turgidum var. dicoccoides) and previously mapped to the distal region of chromosome 3BL bin 0.63-1.00, was constructed using an F5:6 recombinant inbred line population derived from a cross of durum wheat cultivar Langdon and wild emmer accession IW2. By applying comparative genomics analyses, 19 polymorphic sequence-tagged site markers were developed and integrated into the Pm41 genetic linkage map. Ultimately, Pm41 was mapped in a 0.6 cM genetic interval flanked by markers XWGGC1505 and XWGGC1507, which correspond to 11.7, 19.2, and 24.9 kb orthologous genomic regions in Brachypodium, rice, and sorghum, respectively. The XWGGC1506 marker co-segregated with Pm41 and could be served as a starting point for chromosome landing and map-based cloning as well as marker-assisted selection of Pm41. Detailed comparative genomics analysis of the markers flanking the Pm41 locus in wheat and the putative orthologous genes in Brachypodium, rice, and sorghum suggests that the gene order is highly conserved between rice and sorghum. However, intra-chromosome inversions and re-arrangements are evident in the wheat and Brachypodium genomic regions, and gene duplications are also present in the orthologous genomic regions of Pm41 in wheat, indicating that the Brachypodium gene model can provide more useful information for wheat marker development.