Enrichment and Diversification of the Wheat Genome via Alien Introgression.

Wheat, including durum and common wheat, respectively, is an allopolyploid with two or three homoeologous subgenomes originating from diploid wild ancestral species. The wheat genome's polyploid origin consisting of just three diploid ancestors has constrained its genetic variation, which has bottlenecked improvement. However, wheat has a large number of relatives, including cultivated crop species (e.g., barley and rye), wild grass species, and ancestral species. Moreover, each ancestor and relative has many other related subspecies that have evolved to inhabit specific geographic areas. Cumulatively, they represent an invaluable source of genetic diversity and variation available to enrich and diversify the wheat genome. The ancestral species share one or more homologous genomes with wheat, which can be utilized in breeding efforts through typical meiotic homologous recombination. Additionally, genome introgressions of distant relatives can be moved into wheat using chromosome engineering-based approaches that feature induced meiotic homoeologous recombination. Recent advances in genomics have dramatically improved the efficacy and throughput of chromosome engineering for alien introgressions, which has served to boost the genetic potential of the wheat genome in breeding efforts. Here, we report research strategies and progress made using alien introgressions toward the enrichment and diversification of the wheat genome in the genomics era.

A Comparative Study on Fixed-order Event Sequence Visualizations: Gantt, Extended Gantt, and Stringline Charts.

We conduct two in-lab experiments (N=93) to evaluate the effectiveness of Gantt charts, extended Gantt charts, and stringline charts for visualizing fixed-order event sequence data. We first formulate five types of event sequences and define three types of sequence elements: point events, interval events, and the temporal gaps between them. Our two experiments focus on event sequences with a pre-defined, fixed order, and measure task error rates and completion time. The first experiment shows single sequences and assesses the three charts' performance in comparing event duration or gap. The second experiment shows multiple sequences and evaluates how well the charts reveal temporal patterns. The results suggest that when visualizing single fixed-order event sequences, 1) Gantt and extended Gantt charts lead to comparable error rates in the duration-comparing task; 2) Gantt charts exhibit either shorter or equal completion time than extended Gantt charts; 3) both Gantt and extended Gantt charts demonstrate shorter completion times than stringline charts; 4) however, stringline charts outperform the other two charts with fewer errors in the comparing task when event type counts are high. Additionally, when visualizing multiple point-based fixed-order event sequences, stringline charts require less time than Gantt charts for people to find temporal patterns. Based on these findings, we discuss design opportunities for visualizing fixed-order event sequences and discuss future avenues for optimizing these charts.

Genetic analysis of basal stalk rot resistance introgressed from wild Helianthus petiolaris into cultivated sunflower (Helianthus annuus L.) using an advanced backcross population.

Introduction: Sclerotinia sclerotiorum is a serious pathogen causing severe basal stalk rot (BSR) disease on cultivated sunflower (Helianthus annuus L.) that leads to significant yield losses due to insufficient resistance. The wild annual sunflower species H. petiolaris, commonly known as prairie sunflower is known for its resistance against this pathogen. Sunflower resistance to BSR is quantitative and determined by many genes with small effects on the resistance phenotype. The objective of this study was to identify loci governing BSR resistance derived from H. petiolaris using a quantitative trait loci (QTL) mapping approach. Methods: BSR resistance among lines of an advanced backcross population (AB-QTL) with 174 lines developed from a cross of inbred line HA 89 with H. petiolaris PI 435843 was determined in the field during 2017-2019, and in the greenhouse in 2019. AB-QTL lines and the HA 89 parent were genotyped using genotyping-by-sequencing and a genetic linkage map was developed spanning 997.51 cM and using 1,150 SNP markers mapped on 17 sunflower chromosomes. Results and discussion: Highly significant differences (p<0.001) for BSR response among AB-QTL lines were observed disease incidence (DI) in all field seasons, as well as disease rating (DR) and area under the disease progress curve (AUDPC) in the greenhouse with a moderately high broad-sense heritability (H 2) of 0.61 for the tested resistance parameters. A total of 14 QTL associated with BSR resistance were identified on nine chromosomes, each explaining a proportion of the phenotypic variation ranging from 3.5% to 28.1%. Of the 14 QTL, eight were detected for BSR resistance in the field and six were detected under greenhouse conditions. Alleles conferring increased BSR resistance were contributed by the H. petiolaris parent at 11 of the 14 QTL.

Agronomic Evaluation and Molecular Cytogenetic Characterization of Triticum aestivum × Thinopyrum spp. Derivative Breeding Lines Presenting Perennial Growth Habits.

The transition from annual to perennial growth habits can contribute to increased sustainability and diversification of staple cropping systems like those based on annual wheat. Amphiploids between Triticum aestivum and Thinopyrum spp. can present a wheat-like morphology and post sexual cycle regrowth. The complex and unpredictable nature of the chromosomal rearrangements typical of inter-generic hybrids can hamper progress in the development of this new crop. By using fluorescence in situ hybridization, we described the genomic constitution of three perennial wheat breeding lines that regrew and completed a second year of production in field conditions in Washington state (USA). Two breeding lines presented stable, 56-chromosome partial amphiploids; however, their chromosome composition differed significantly. The third breeding line presented an unstable karyotype with a chromosome number ranging from 53 to 58 across eight individuals. The agronomic performance of the perennial breeding lines was evaluated for two growing seasons from 2020 to 2022. The grain yields of the perennial lines were lower than the grain production of the annual wheat control line in the first season. The perennial lines displayed vigorous regrowth after the initial harvest; however, worsening environmental conditions in the second season of growth hampered subsequent growth and grain yield. This information facilitates the breeding work necessary to improve key traits by grouping agronomically valuable individuals according to their genomic constitution.

Genome-wide association analyses of leaf rust resistance in cultivated emmer wheat.

KEY MESSAGE: Fifteen and eleven loci, with most loci being novel, were identified to associate with seedling and adult resistances, respectively, to the durum-specific races of leaf rust pathogen in cultivated emmer. Leaf rust, caused by Puccinia triticina (Pt), constantly threatens durum (Triticum turgidum ssp. durum) and bread wheat (Triticum aestivum) production worldwide. A Pt race BBBQD detected in California in 2009 poses a potential threat to durum production in North America because resistance source to this race is rare in durum germplasm. To find new resistance sources, we assessed a panel of 180 cultivated emmer wheat (Triticum turgidum ssp. dicoccum) accessions for seedling resistance to BBBQD and for adult resistance to a mixture of durum-specific races BBBQJ, CCMSS, and MCDSS in the field, and genotyped the panel using genotype-by-sequencing (GBS) and the 9 K SNP (Single Nucleotide Polymorphism) Infinium array. The results showed 24 and nine accessions consistently exhibited seedling and adult resistance, respectively, with two accessions providing resistance at both stages. We performed genome-wide association studies using 46,383 GBS and 4,331 9 K SNP markers and identified 15 quantitative trait loci (QTL) for seedling resistance located mostly on chromosomes 2B and 6B, and 11 QTL for adult resistance on 2B, 3B and 6A. Of these QTL, one might be associated with leaf rust resistance (Lr) gene Lr53, and two with the QTL previously reported in durum or hexaploid wheat. The remaining QTL are potentially associated with new Lr genes. Further linkage analysis and gene cloning are necessary to identify the causal genes underlying these QTL. The emmer accessions with high levels of resistance will be useful for developing mapping populations and adapted durum germplasm and varieties with resistance to the durum-specific races.

Cytogenetic and genomic characterization of a novel tall wheatgrass-derived Fhb7 allele integrated into wheat B genome.

KEY MESSAGE: We identified and integrated the novel FHB-resistant Fhb7The2 allele into wheat B genome and made it usable in both common and durum wheat breeding programs without yellow flour linkage drag. A novel tall wheatgrass-derived (Thinopyrum elongatum, genome EE) Fhb7 allele, designated Fhb7The2, was identified and integrated into the wheat B genome through a small 7B-7E translocation (7BS·7BL-7EL) involving the terminal regions of the long arms. Fhb7The2 conditions significant Type II resistance to Fusarium head blight (FHB) in wheat. Integration of Fhb7The2 into the wheat B genome makes this wild species-derived FHB resistance gene usable for breeding in both common and durum wheat. By contrast, other Fhb7 introgression lines involving wheat chromosome 7D can be utilized only in common wheat breeding programs, not in durum wheat. Additionally, we found that Fhb7The2 does not have the linkage drag of the yellow flour pigment gene that is tightly linked to the decaploid Th. ponticum-derived Fhb7 allele Fhb7Thp. This will further improve the utility of Fhb7The2 in wheat breeding. DNA sequence analysis identified 12 single nucleotide polymorphisms (SNPs) in Fhb7The2, Fhb7Thp, and another Th. elongatum-derived Fhb7 allele Fhb7The1, which led to seven amino acid conversions in Fhb7The2, Fhb7Thp, and Fhb7The1, respectively. However, no significant variation was observed in their predicted protein configuration as a glutathione transferase. Diagnostic DNA markers were developed specifically for Fhb7The2. The 7EL segment containing Fhb7The2 in the translocation chromosome 7BS·7BL-7EL exhibited a monogenic inheritance pattern in the wheat genetic background. This will enhance the efficacy of marker-assisted selection for Fhb7The2 introgression, pyramiding, and deployment in wheat germplasm and varieties.

A Quantitative Genetic Study of Sclerotinia Head Rot Resistance Introgressed from the Wild Perennial Helianthus maximiliani into Cultivated Sunflower (Helianthus annuus L.).

Sclerotinia head rot (HR), caused by Sclerotinia sclerotiorum, is an economically important disease of sunflower with known detrimental effects on yield and quality in humid climates worldwide. The objective of this study was to gain insight into the genetic architecture of HR resistance from a sunflower line HR21 harboring HR resistance introgressed from the wild perennial Helianthus maximiliani. An F2 population derived from the cross of HA 234 (susceptible-line)/HR21 (resistant-line) was evaluated for HR resistance at two locations during 2019−2020. Highly significant genetic variations (p < 0.001) were observed for HR disease incidence (DI) and disease severity (DS) in both individual and combined analyses. Broad sense heritability (H2) estimates across environments for DI and DS were 0.51 and 0.62, respectively. A high-density genetic map of 1420.287 cM was constructed with 6315 SNP/InDel markers developed using genotype-by-sequencing technology. A total of 16 genomic regions on eight sunflower chromosomes, 1, 2, 10, 12, 13, 14, 16 and 17 were associated with HR resistance, each explaining between 3.97 to 16.67% of the phenotypic variance for HR resistance. Eleven of these QTL had resistance alleles from the HR21 parent. Molecular markers flanking the QTL will facilitate marker-assisted selection breeding for HR resistance in sunflower.

Genomic Insights Into Sclerotinia Basal Stalk Rot Resistance Introgressed From Wild Helianthus praecox Into Cultivated Sunflower (Helianthus annuus L.).

Crop wild relatives of the cultivated sunflower (Helianthus annuus L.) are a valuable resource for its sustainable production. Helianthus praecox ssp. runyonii is a wild sunflower known for its resistance against diseases caused by the fungus, Sclerotinia sclerotiorum (Lib.) de Bary, which infects over 400 broadleaf hosts including many important food crops. The objective of this research was to dissect the Sclerotinia basal stalk rot (BSR) resistance introgressed from H. praecox ssp. runyonii into cultivated sunflower. An advanced backcross quantitative trait loci (AB-QTL) mapping population was developed from the cross of a H. praecox accession with cultivated sunflower lines. The AB-QTL population was evaluated for BSR resistance in the field during the summers of 2017-2018 and in the greenhouse in the spring of 2018. Highly significant genetic variations (p < 0.001) were observed for the BSR disease in the field and greenhouse with a moderately high broad-sense heritability (H 2) ranging from 0.66 to 0.73. Genotyping-by-sequencing approach was used to genotype the parents and the progeny lines of the AB-QTL population. A genetic linkage map spanning 1,802.95 cM was constructed using 1,755 single nucleotide polymorphism (SNP) markers mapped on 17 sunflower chromosomes. A total of 19 BSR resistance QTL were detected on nine sunflower chromosomes, each explaining 2.21%-16.99% of the phenotypic variance for resistance in the AB-QTL population. Sixteen of the 19 QTL had alleles conferring increased BSR resistance derived from the H. praecox parent. SNP markers flanking the identified QTL will facilitate marker-assisted breeding to combat the disease in sunflower.

Haplotype variants of Sr46 in Aegilops tauschii, the diploid D genome progenitor of wheat.

KEY MESSAGE: Stem rust resistance genes, SrRL5271 and Sr672.1 as well as SrCPI110651, from Aegilops tauschii, the diploid D genome progenitor of wheat, are sequence variants of Sr46 differing by 1-2 nucleotides leading to non-synonymous amino acid substitutions. The Aegilops tauschii (wheat D-genome progenitor) accessions RL 5271 and CPI110672 were identified as resistant to multiple races (including the Ug99) of the wheat stem rust pathogen Puccinia graminis f. sp. tritici (Pgt). This study was conducted to identify the stem rust resistance (Sr) gene(s) in both accessions. Genetic analysis of the resistance in RL 5271 identified a single dominant allele (SrRL5271) controlling resistance, whereas resistance segregated at two loci (SR672.1 and SR672.2) for a cross of CPI110672. Bulked segregant analysis placed SrRL5271 and Sr672.1 in a region on chromosome arm 2DS that encodes Sr46. Molecular marker screening, mapping and genomic sequence analysis demonstrated SrRL5271 and Sr672.1 are alleles of Sr46. The amino acid sequence of SrRL5271 and Sr672.1 is identical but differs from Sr46 (hereafter referred to as Sr46_h1 by following the gene nomenclature in wheat) by a single amino acid (N763K) and is thus designated Sr46_h2. Screening of a panel of Ae. tauschii accessions identified an additional allelic variant that differed from Sr46_h2 by a different amino acid (A648V) and was designated Sr46_h3. By contrast, the protein encoded by the susceptible allele of Ae. tauschii accession AL8/78 differed from these resistance proteins by 54 amino acid substitutions (94% nucleotide sequence gene identity). Cloning and complementation tests of the three resistance haplotypes confirmed their resistance to Pgt race 98-1,2,3,5,6 and partial resistance to Pgt race TTRTF in bread wheat. The three Sr46 haplotypes, with no virulent races detected yet, represent a valuable source for improving stem resistance in wheat.

Genomic compatibility and inheritance of hexaploid-derived Fusarium head blight resistance genes in durum wheat.

Hexaploid-derived resistance genes exhibit complex inheritance and expression patterns in tetraploid backgrounds. This study aimed to characterize the inheritance patterns and genomic compatibilities of hexaploid-derived Fusarium head blight (FHB) resistance genes in tetraploid durum wheat (Triticum durum Desf.). Evaluation of FHB resistance for F1 hybrids of hexaploid 'Sumai 3' crossed with tetraploid and hexaploid wheats indicated that Sumai 3-derived FHB resistance genes exhibit a dominant phenotypic effect seen only in hexaploid hybrids. Alternately, the hexaploid-derived FHB resistance genes from PI 277012 exhibited complete dominance in the crosses with both tetraploid and hexaploid wheat. FHB evaluation of the F1 hybrids of Sumai 3 and PI 277012 crossed with 'Langdon' (LDN)-'Chinese Spring' D-genome substitution lines suggested that chromosomes 2B, 3B, 4B, 5B, 6B, 3A, 4A, 6A, and 7A contain genes that suppress expression of the Sumai 3-derived FHB resistance, whereas chromosomes 4A, 6A, and 6B contain genes required for expression of PI 277012-derived FHB resistance. A wide range of segregation for FHB severity (10-90%) was observed in the F2 generation of Sumai 3 crossed with durum cultivars LDN and 'Divide', but the distribution of F3 families derived from the most resistant F2 segregants was skewed towards susceptibility. Similar segregation trends were observed in the crosses of PI 277012 with other durum wheats, whereby FHB resistance became slightly diluted over successive generations. These results suggest tetraploid durum wheat contains the unique alleles at multiple gene loci on different chromosomes that positively and/or negatively regulate the expression of hexaploid-derived FHB resistance genes, which complicate efforts to deploy these genes in durum breeding programs.

Function and evolution of allelic variations of Sr13 conferring resistance to stem rust in tetraploid wheat (Triticum turgidum L.).

The resistance gene Sr13 is one of the most important genes in durum wheat for controlling stem rust caused by Puccinia graminis f. sp. tritici (Pgt). The Sr13 functional gene CNL13 has haplotypes R1, R2 and R3. The R1/R3 and R2 haplotypes were originally designated as alleles Sr13a and Sr13b, respectively. To detect additional Sr13 alleles, we developed Kompetitive allele specific PCR (KASP™) marker KASPSr13 and four semi-thermal asymmetric reverse PCR markers, rwgsnp37-rwgsnp40, based on the CNL13 sequence. These markers were shown to detect R1, R2 and R3 haplotypes in a panel of diverse tetraploid wheat accessions. We also observed the presence of Sr13 in durum line CAT-A1, although it lacked any of the known haplotypes. Sequence analysis revealed that CNL13 of CAT-A1 differed from the susceptible haplotype S1 by a single nucleotide (C2200T) in the leucine-rich repeat region and differed from the other three R haplotypes by one or two additional nucleotides, confirming that CAT-A1 carries a new (R4) haplotype. Stem rust tests on the monogenic, transgenic and mutant lines showed that R1 differed from R3 in its susceptibility to races TCMJC and THTSC, whereas R4 differed from all other haplotypes for susceptibility to TTKSK, TPPKC and TCCJC. Based on these differences, we designate the R1, R3 and R4 haplotypes as alleles Sr13a, Sr13c and Sr13d, respectively. This study indicates that Sr13d may be the primitive functional allele originating from the S1 haplotype via a point mutation, with the other three R alleles probably being derived from Sr13d through one or two additional point mutations.

A Surrogate-Assisted Multiswarm Optimization Algorithm for High-Dimensional Computationally Expensive Problems.

This article presents a surrogate-assisted multiswarm optimization (SAMSO) algorithm for high-dimensional computationally expensive problems. The proposed algorithm includes two swarms: the first one uses the learner phase of teaching-learning-based optimization (TLBO) to enhance exploration and the second one uses the particle swarm optimization (PSO) for faster convergence. These two swarms can learn from each other. A dynamic swarm size adjustment scheme is proposed to control the evolutionary progress. Two coordinate systems are used to generate promising positions for the PSO in order to further enhance its search efficiency on different function landscapes. Moreover, a novel prescreening criterion is proposed to select promising individuals for exact function evaluations. Several commonly used benchmark functions with their dimensions varying from 30 to 200 are adopted to evaluate the proposed algorithm. The experimental results demonstrate the superiority of the proposed algorithm over three state-of-the-art algorithms.

Dissection and physical mapping of wheat chromosome 7B by inducing meiotic recombination with its homoeologues in Aegilops speltoides and Thinopyrum elongatum.

KEY MESSAGE: We constructed a homoeologous recombination-based bin map of wheat chromosome 7B, providing a unique physical framework for further study of chromosome 7B and its homoeologues in wheat and its relatives. Homoeologous recombination leads to the dissection and diversification of the wheat genome. Advances in genome sequencing and genotyping have dramatically improved the efficacy and throughput of homoeologous recombination-based genome studies and alien introgression in wheat and its relatives. In this study, we aimed to physically dissect and map wheat chromosome 7B by inducing meiotic recombination of chromosome 7B with its homoeologues 7E in Thinopyrum elongatum and 7S in Aegilops speltoides. The special genotypes, which were double monosomic for chromosomes 7B' + 7E' or 7B' + 7S' and homozygous for the ph1b mutant, were produced to enhance 7B - 7E and 7B - 7S recombination. Chromosome-specific DNA markers were developed and used to pre-screen the large recombination populations for 7B - 7E and 7B - 7S recombinants. The DNA marker-mediated preselections were verified by fluorescent genomic in situ hybridization (GISH). In total, 29 7B - 7E and 61 7B - 7S recombinants and multiple chromosome aberrations were recovered and delineated by GISH and the wheat 90 K SNP assay. Integrated GISH and SNP analysis of the recombinants physically mapped the recombination breakpoints and partitioned wheat chromosome 7B into 44 bins with 523 SNPs assigned within. A composite bin map was constructed for chromosome 7B, showing the bin size and physical distribution of SNPs. This provides a unique physical framework for further study of chromosome 7B and its homoeologues. In addition, the 7B - 7E and 7B - 7S recombinants extend the genetic variability of wheat chromosome 7B and represent useful germplasm for wheat breeding. Thereby, this genomics-enabled chromosome engineering approach facilitates wheat genome study and enriches the gene pool of wheat improvement.

Genetic Dissection of Phomopsis Stem Canker Resistance in Cultivated Sunflower Using High Density SNP Linkage Map.

Phomopsis stem canker (PSC) caused by Diaporthe helianthi is increasingly becoming a global threat for sunflower production. In this study, the genetic basis of PSC resistance was investigated in a recombinant inbred line (RIL) population developed from a cross between HA 89 (susceptible) and HA-R3 (resistant). The RIL population was evaluated for PSC disease incidence (DI) in seven screening trials at multiple locations during 2016-2018. The distribution of PSC DI in the RIL population was continuous, confirming a polygenic inheritance of the trait. A moderately high broad-sense heritability (H2, 0.76) was estimated for the trait across environments. In the combined analysis, both the genotype and the genotype × environment interactions were highly significant. A linkage map spanning 1505.33 cM was constructed using genotyping-by-sequencing derived markers. Marker-trait association analysis identified a total of 15 quantitative trait loci (QTL) associated with PSC resistance on 11 sunflower chromosomes, each explaining between 5.24 and 17.39% of the phenotypic variation. PSC resistance QTL were detected in two genomic regions each on chromosomes 3, 5, 13, and 17, while one QTL each was detected in the remaining seven chromosomes. Tightly linked single nucleotide polymorphism (SNP) markers flanking the PSC resistance QTL will facilitate marker-assisted selection in PSC resistance sunflower breeding.

Partitioning and physical mapping of wheat chromosome 3B and its homoeologue 3E in Thinopyrum elongatum by inducing homoeologous recombination.

KEY MESSAGE: We performed homoeologous recombination-based partitioning and physical mapping of wheat chromosome 3B and Th. elongatum chromosome 3E, providing a unique physical framework of this homoeologous pair for genome studies. The wheat (Triticum aestivum, 2n = 6x = 42, AABBDD) and Thinopyrum elongatum (2n = 2x = 14, EE) genomes can be differentiated from each other by fluorescent genomic in situ hybridization (FGISH) as well as molecular markers. This has facilitated homoeologous recombination-based partitioning and engineering of their genomes for physical mapping and alien introgression. Here, we constructed a special wheat genotype, which was double monosomic for wheat chromosome 3B and Th. elongatum chromosome 3E and homozygous for the ph1b mutant, to induce 3B-3E homoeologous recombination. Totally, 81 3B-3E recombinants were recovered and detected in the primary, secondary, and tertiary homoeologous recombination cycles by FGISH. Comparing to the primary recombination, the secondary and tertiary recombination shifted toward the proximal regions due to the increase in homology between the pairing partners. The 3B-3E recombinants were genotyped by high-throughput wheat 90-K single nucleotide polymorphism (SNP) arrays and their recombination breakpoints physically mapped based on the FGISH patterns and SNP results. The 3B-3E recombination physically partitioned chromosome 3B into 38 bins, and 429 SNPs were assigned to the distinct bins. Integrative analysis of FGISH and SNP results led to the construction of a composite bin map for chromosome 3B. Additionally, we developed 22 SNP-derived semi-thermal asymmetric reverse PCR markers specific for chromosome 3E and constructed a comparative map of homoeologous chromosomes 3E, 3B, 3A, and 3D. In summary, this work provides a unique physical framework for further studies of the 3B-3E homoeologous pair and diversifies the wheat genome for wheat improvement.

Unraveling the Sclerotinia Basal Stalk Rot Resistance Derived From Wild Helianthus argophyllus Using a High-Density Single Nucleotide Polymorphism Linkage Map.

Basal stalk rot (BSR), caused by the fungus Sclerotinia sclerotiorum, is a serious disease of sunflower (Helianthus annuus L.) in the humid temperate growing areas of the world. BSR resistance is quantitative and conditioned by multiple genes. Our objective was to dissect the BSR resistance introduced from the wild annual species Helianthus argophyllus using a quantitative trait loci (QTL) mapping approach. An advanced backcross population (AB-QTL) with 134 lines derived from the cross of HA 89 with a H. argophyllus Torr. and Gray accession, PI 494573, was evaluated for BSR resistance in three field and one greenhouse growing seasons of 2017-2019. Highly significant genetic variations (p < 0.001) were observed for BSR disease incidence (DI) in all field screening tests and disease rating and area under the disease progress curve in the greenhouse. The AB-QTL population and its parental lines were genotyped using the genotyping-by-sequencing method. A genetic linkage map spanning 2,045.14 cM was constructed using 3,110 SNP markers mapped on 17 sunflower chromosomes. A total of 21 QTL associated with BSR resistance were detected on 11 chromosomes, each explaining a phenotypic variation ranging from 4.5 to 22.6%. Of the 21 QTL, eight were detected for BSR DI measured in the field, seven were detected for traits measured in the greenhouse, and six were detected from both field and greenhouse tests. Thirteen of the 21 QTL had favorable alleles from the H. argophyllus parent conferring increased BSR resistance.

Chromosome engineering-mediated introgression and molecular mapping of novel Aegilops speltoides-derived resistance genes for tan spot and Septoria nodorum blotch diseases in wheat.

KEY MESSAGE: We identified, mapped and introduced novel Aegilops speltoides-derived resistance genes for tan spot and SNB diseases into wheat, enhancing understanding and utilization of host resistance to both diseases in wheat. Tan spot and Septoria nodorum blotch (SNB) are two important fungal diseases of wheat. Resistance to these diseases is often observed as the lack of sensitivity to the necrotrophic effectors (NE) produced by the fungal pathogens and thus exhibits a recessive inheritance pattern. In this study, we identified novel genes for resistance to tan spot and SNB on Aegilops speltoides (2n = 2x = 14, genome SS) chromosome 2S. These genes confer dominant resistance in the wheat background, indicating a distinct NE-independent mechanism of resistance. Ae. speltoides chromosome 2S was engineered for resistance gene introgression and molecular mapping by inducing meiotic homoeologous recombination with wheat chromosome 2B. Twenty representative 2B-2S recombinants were evaluated for reaction to tan spot and SNB and were delineated by genomic in situ hybridization and high-throughput wheat 90 K SNP assay. The resistance genes physically mapped to the sub-telomeric region (~ 8 Mb) on the short arm of chromosome 2S and designated TsrAes1 for tan spot resistance and SnbAes1 for SNB resistance. In addition, we developed SNP-derived PCR markers closely linked to TsrAes1/SnbAes1 for marker-assisted selection in wheat breeding. TsrAes1 and SnbAes1 are the first set of NE-independent tan spot, and SNB resistance genes are identified from Ae. speltoides. The 2SS-2BS·2BL recombinants with minimal amounts of Ae. speltoides chromatin containing TsrAes1/SnbAes1 were produced for germplasm development, making the wild species-derived resistance genes usable in wheat breeding. This will strengthen and diversify resistance of wheat to tan spot and SNB and facilitate understanding of resistance to these two diseases.

A Semantic-Based Method for Visualizing Large Image Collections.

Interactive visualization of large image collections is important and useful in many applications, such as personal album management and user profiling on images. However, most prior studies focus on using low-level visual features of images, such as texture and color histogram, to create visualizations without considering the more important semantic information embedded in images. This paper proposes a novel visual analytic system to analyze images in a semantic-aware manner. The system mainly comprises two components: a semantic information extractor and a visual layout generator. The semantic information extractor employs an image captioning technique based on convolutional neural network (CNN) to produce descriptive captions for images, which can be transformed into semantic keywords. The layout generator employs a novel co-embedding model to project images and the associated semantic keywords to the same 2D space. Inspired by the galaxy metaphor, we further turn the projected 2D space to a galaxy visualization of images, in which semantic keywords and images are visually encoded as stars and planets. Our system naturally supports multi-scale visualization and navigation, in which users can immediately see a semantic overview of an image collection and drill down for detailed inspection of a certain group of images. Users can iteratively refine the visual layout by integrating their domain knowledge into the co-embedding process. Two task-based evaluations are conducted to demonstrate the effectiveness of our system.

Delimitation of wheat ph1b deletion and development of ph1b-specific DNA markers.

KEY MESSAGE: We detected the deletion breakpoints of wheat ph1b mutant and the actual size of the deletion. Also, we developed ph1b deletion-specific markers useful for ph1b-mediated gene introgression and genome studies. The Ph1 (pairing homoeologous) locus has been considered a major genetic system for the diploidized meiotic behavior of the allopolyploid genome in wheat. It functions as a defense system against meiotic homoeologous pairing and recombination in polyploid wheat. A large deletion of the genomic region harboring Ph1 on the long arm of chromosome 5B (5BL) led to the ph1b mutant in hexaploid wheat 'Chinese Spring,' which has been widely used to induce meiotic homoeologous recombination for gene introgression from wild grasses into wheat. However, the breakpoints and physical size of the deletion remain undetermined. In the present study, we first anchored the ph1b deletion on 5BL by the high-throughput wheat 90K SNP assay and then delimited the deletion to a genomic region of 60,014,523 bp by chromosome walking. DNA marker and sequence analyses detected the nucleotide positions of the distal and proximal breakpoints (DB and PB) of the ph1b deletion and the deletion junction as well. This will facilitate understanding of the genomic region harboring the Ph1 locus in wheat. In addition, we developed user-friendly DNA markers specific for the ph1b deletion. These new ph1b deletion-specific markers will dramatically improve the efficacy of the ph1b mutant in the meiotic homoeologous recombination-based gene introgression and genome studies in wheat and its relatives.

Molecular and Cytogenetic Characterization of Six Wheat-Aegilops markgrafii Disomic Addition Lines and Their Resistance to Rusts and Powdery Mildew.

Aegilops markgrafii (Greuter) Hammer is an important source of genes for resistance to abiotic stresses and diseases in wheat (Triticum aestivum L.). A series of six wheat 'Alcedo'-Ae. markgrafii chromosome disomic addition lines, designated as AI(B), AII(C), AIII(D), AV(E), AIV(F), and AVIII(G) carrying the Ae. markgrafii chromosomes B, C, D, E, F, and G, respectively, were tested with SSR markers to establish homoeologous relationships to wheat and identify markers useful in chromosome engineering. The addition lines were evaluated for resistance to rust and powdery mildew diseases. The parents Alcedo and Ae. markgrafii accession 'S740-69' were tested with 1500 SSR primer pairs and 935 polymorphic markers were identified. After selecting for robust markers and confirming the polymorphisms on the addition lines, 132 markers were considered useful for engineering and establishing homoeologous relationships. Based on the marker analysis, we concluded that the chromosomes B, C, D, E, F, and G belong to wheat homoeologous groups 2, 5, 6, 7, 3, and 4, respectively. Also, we observed chromosomal rearrangements in several addition lines. When tested with 20 isolates of powdery mildew pathogen (Blumeria graminis f. sp. tritici) from five geographic regions of the United States, four addition lines [AIII(D), AV(E), AIV(F), and AVIII(G)] showed resistance to some isolates, with addition line AV(E) being resistant to 19 of 20 isolates. The addition lines were tested with two races (TDBJ and TNBJ) of the leaf rust pathogen (Puccinia triticina), and only addition line AI(B) exhibited resistance at a level comparable to the Ae. markgrafii parent. Addition lines AII(C) and AIII(D) had been previously identified as resistant to the Ug99 race group of the stem rust pathogen (Puccinia graminis f. sp. tritici). The addition lines were also tested for resistance to six United States races (PSTv-4, PSTv-14, PSTv-37, PSTv-40, PSTv-51, and PSTv-198) of the stripe rust pathogen (Puccinia striiformis f. sp. tritici); we found no resistance either in Alcedo or any of the addition lines. The homoeologous relationships of the chromosomes in the addition lines, molecular markers located on each chromosome, and disease resistance associated with each chromosome will allow for chromosome engineering of the resistance genes.