Molecular cytogenetic identification of a wheat–Psathyrostachys huashanica Keng 5Ns disomic addition line with stripe rust resistance

We developed a new stripe rust resistant line of common wheat–Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) from a cross between wheat cv. 7182 and P. huashanica via embryo culture, and we refer to this line as 3-8-10-2. We characterized this new line by cytology, genomic in situ hybridization (GISH), EST-SSR, EST-STS, and disease resistance screening. GISH using P. huashanica genomic DNA as the probe indicated that a pair of Ns chromosomes with strong hybridization signals was introduced into 3-8-10-2. We screened 255 EST-SSR and EST-STS multiple-loci markers from seven wheat homoeologous groups in the parent lines. Of these, 90 markers were polymorphic with a polymorphism frequency of 40 %, while two EST-SSR markers and six EST-STS markers located on wheat chromosome group 5 produced specific bands in P. huashanica and 3-8-10-2, respectively. This suggested that the introduced Ns chromosome pair belonged to homoeologous group 5, which was identified using new genome-specific markers. After inoculation with stripe rust isolates, 3-8-10-2 exhibited stripe rust resistance that probably originated from its P. huashanica parent. 3-8-10-2 can be used as a donor source for introducing novel disease resistance genes into wheat during breeding programs with the assistance of molecular and cytogenetic markers. Moreover, 3-8-10-2 had improved agronomic characteristics compared with its parents. Therefore, the addition line could be exploited as an important bridge for wheat breeding and chromosome engineering.     

Molecular characterization of a wheat–Psathyrostachys huashanica Keng 2Ns disomic addition line with resistance to stripe rust

We characterized a wheat–Psathyrostachys huashanica derived line 3-6-4-1 based on genomic in situ hybridization (GISH), molecular marker analysis, and agronomic trait evaluations. The GISH investigations showed that the 3-6-4-1 contained 42 wheat chromosomes and a pair of P. huashanica chromosomes. The homoeologous relationships of the introduced P. huashanica chromosomes were determined using EST-STS multiple loci markers from seven wheat homoeologous groups in the parents and the addition line. Twelve EST-STS markers located on the homoeologous group 2 chromosomes of wheat amplified polymorphic bands in 3-6-4-1, which were unique to P. huashanica. An introduced Ns chromosome pair that belonged to homoeologous group 2 was identified using chromosome-specific markers. Inoculation with isolates of the stripe rust pathotypes, CYR31, CYR32, and SY11-14, and mixed races (CYR31, CYR32, and SY11-14) in the seeding and adult stage, respectively, showed that 3-6-4-1 was generally resistant to stripe rust, which was probably attributable to its P. huashanica parent. We also compared a complete set of wheat–P. huashanica disomic addition lines (1Ns–7Ns, 2n = 44 = 22II) to assess their agronomic traits and morphological characteristics, which showed that 3-6-4-1 had improved spike traits compared with its parents. The P. huashanica 2Ns chromosome-specific molecular markers in 3-6-4-1 could be useful for marker-assisted selection in breeding programs to combat stripe rust. This line can be used as a donor source to introduce novel excellent genes from P. huashanica into wheat to widen its genetic diversity, thereby providing new germplasms for wheat breeding.     

Characterization of a wheat-Psathyrostachys huashanica Keng 4Ns disomic addition line for enhanced tiller numbers and stripe rust resistance

Exploiting and utilizing excellent gene(s) from wild species has become an essential strategy for wheat improvement. In the disomic addition line 24-6-3, the 4Ns chromosomes from Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) carried valuable tiller and strip rust resistance gene(s), which was selected from the progeny of common wheat cv. 7182 and P. huashanica via embryo culture. Cytology, genomic in situ hybridization (GISH), and EST-STS analyses were used to detect the 4Ns chromosome in wheat background and its homoeologous relationship. Cytological studies demonstrated that 24-6-3 contained 44 chromosomes and formed 22 bivalents during meiotic metaphase I. GISH using P. huashanica genomic DNA as a probe indicated that a pair of Ns-chromosomes with strong hybridization signals had been introduced into 24-6-3. Ten EST-STS markers, i.e., BE404973, BE442811, BE446061, BE446076, BE497324, BE591356, BF473854, BG274986, BQ161513 and CD373484, which were located on the homoeologous group 4 chromosomes of wheat, amplified bands unique to P. huashanica in 24-6-3. This indicated the presence of an introgressed P. huashanica Ns chromosome pair belonging to homoeologous group 4, which we designated the 4Ns disomic addition line. After it was inoculated using mixed races of stripe rust in the adult stages, 24-6-3 expressed high stripe rust resistance, which was possibly derived from its P. huashanica parent. Moreover, its increased number of tillers was probably controlled by gene(s) located in P. huashanica chromosome 4Ns. These high levels of disease resistance and excellent agronomic traits make the 24-6-3 line a promising germplasm for breeding in wheat.     

Anatomy and Cytogenetic Identification of a Wheat-Psathyrostachys huashanica Keng Line with Early Maturation

In previous studies, our research team successfully transferred the Ns genome from Psathyrostachys huashanica Keng into Triticum aestivum (common wheat cv. 7182) using embryo culture. In the present study, one of these lines, i.e., hybrid progeny 25-10-3, which matured about 10–14 days earlier than its wheat parent, was assessed using sequenced characterized amplified region (SCAR) analysis, EST-SSR and EST-STS molecular markers, and genomic in situ hybridization (GISH). We found that this was a stable wheat-P. huashanica disomic addition line (2n = 44 = 22 II) and the results demonstrated that it was a 6Ns disomic chromosome addition line, but it exhibited many different features compared with previously characterized lines, i.e., a longer awn, early maturation, and no twin spikelets. It was considered to be an early-maturing variety based on the early stage of inflorescence initiation in field experiments and binocular microscope observations over three consecutive years. This characteristic was distinct, especially from the single ridge stage and double ridge stage until the glume stage. In addition, it had a higher photosynthesis rate and economic values than common wheat cv. 7182, i.e., more spikelets per spike, more florets per spikelet, more kernels per spike, and a higher thousand-grain weight. These results suggest that this material may comprise a genetic pool of beneficial genes or chromosome segments, which are suitable for introgression to improve the quality of common wheat.     

The 3Ns chromosome of Psathyrostachys huashanica carries the gene(s) underlying wheat stripe rust resistance

Stripe rust (Puccinia striiformis tritici (Pst)) is one of the most destructive diseases of wheat in the world. Exploiting and utilizing stripe rust resistance genes of wild species has become an essential strategy for resistance breeding. Psathyrostachyshuashanica Keng ex Kuo is a wild species in Triticeae that has been used for wheat improvement because of its high resistance or immunity to stripe rust. In this study, 9 wheat-P. huashanica addition lines were characterized by Giemsa C-banding, genomic in situ hybridization (GISH), and disease resistance evaluation. Giemsa C-banding and GISH demonstrated that lines 163-5, 165-1, 183-5, 240-3, and 240-4 are P. huashanica 3Ns chromosome monosomic addition lines; lines 183-1 and 183-20 are P. huashanica 3Ns chromosome disomic addition lines; line 165-20 is a P. huashanica 3Ns and 4Ns chromosomes double disomic addition line, and line 219-1 is a P. huashanica 1Ns and 3Ns/5A chromosomes double disomic addition-substitution line. All these addition lines with P. huashanica 3Ns chromosome(s) expressed high resistance or immunity to stripe rust. By comparing the series of wheat-P. huashanica chromosome addition lines, we concluded that the P. huashanica 3Ns chromosome carries the gene(s) for resistance or immunity to stripe rust. These addition lines can be used as a donor source of novel stripe rust resistance to wheat breeding programs.     

Introgression of chromosome 3Ns from Psathyrostachys huashanica into wheat specifying resistance to stripe rust

Wheat stripe rust is a destructive disease in the cool and humid wheat-growing areas of the world. Finding diverse sources of stripe rust resistance is critical for increasing genetic diversity of resistance for wheat breeding programs. Stripe rust resistance was identified in the alien species Psathyrostachys huashanica, and a wheat-P. huashanica amphiploid line (PHW-SA) with stripe rust resistance was reported previously. In this study, a P. huashanica 3Ns monosomic addition line (PW11) with superior resistance to stripe rust was developed, which was derived from the cross between PHW-SA and wheat J-11. We evaluated the alien introgressions PW11-2, PW11-5 and PW11-8 which were derived from line PW11 for reaction to new Pst race CYR32, and used molecular and cytogenetic tools to characterize these lines. The introgressions were remarkably resistant to CYR32, suggesting that the resistance to stripe rust of the introgressions thus was controlled by gene(s) located on P. huashanica chromosome 3Ns. All derived lines were cytologically stable in term of meiotic chromosome behavior. Two 3Ns chromosomes of P. huashanica were detected in the disomic addition line PW11-2. Chromosomes 1B of substitution line PW11-5 had been replaced by a pair of P. huashanica 3Ns chromosomes. In PW11-8, a small terminal segment from P. huashanica chromosome arm 3NsS was translocated to the terminal region of wheat chromosomes 3BL. Thus, this translocated chromosome is designated T3BL-3NsS. These conclusions were further confirmed by SSR analyses. Two 3Ns-specific markers Xgwm181 and Xgwm161 will be useful to rapidly identify and trace the translocated fragments. These introgressions, which had significant characteristics of resistance to stripe rust, could be utilized as novel germplasms for wheat breeding.     

Genetic analysis and molecular mapping of a stripe rust resistance gene derived from Psathynrostachys huashanica Keng in wheat line H9014-121-5-5-9

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases worldwide and is also an important disease in China. The wheat translocation line H9014-121-5-5-9 was originally developed from interspecific hybridization between wheat (Triticum aestivum L.) line 7182 and Psathyrostachys huashanica Keng. This translocation line showed resistance to predominant stripe rust races in China when it was tested with nine races of Pst. To determine the inheritance and map the resistance gene, segregating populations were developed from the cross between H9014-121-5-5-9 and the susceptible cultivar Mingxian 169. The seedlings of the F1, F2, and F2:3 generations were tested with race CYR31. The results showed that the resistance in H9014-121-5-5-9 was conferred by a single dominant gene. Bulked segregant analysis and simple sequence repeat (SSR) markers were used to identify polymorphic markers associated with the resistance gene locus. Seven polymorphic SSR markers were linked to the resistance gene. A linkage map was constructed according to the genotypes of the seven SSR markers and the resistance gene. Based on the SSR marker positions on the wheat chromosome, the resistance gene was assigned on chromosome 1AL, temporarily designated YrHA. Based on chromosomal location, reaction patterns and pedigree analysis, YrHA should be a novel resistance gene to stripe rust. The molecular markers of the new resistance gene in H9014-121-5-5-9 could be useful for marker-assisted selection in breeding programs against stripe rust.     

Development and Characterization of a Psathyrostachys huashanica Keng 7Ns Chromosome Addition Line with Leaf Rust Resistance

The aim of this study was to characterize a Triticum aestivum-Psathyrostachys huashanica Keng (2n = 2x = 14, NsNs) disomic addition line 2-1-6-3. Individual line 2-1-6-3 plants were analyzed using cytological, genomic in situ hybridization (GISH), EST-SSR, and EST-STS techniques. The alien addition line 2-1-6-3 was shown to have two P. huashanica chromosomes, with a meiotic configuration of 2n = 44 = 22 II. We tested 55 EST-SSR and 336 EST-STS primer pairs that mapped onto seven different wheat chromosomes using DNA from parents and the P. huashanica addition line. One EST-SSR and nine EST-STS primer pairs indicated that the additional chromosome of P. huashanica belonged to homoeologous group 7, the diagnostic fragments of five EST-STS markers ({"type":"entrez-nucleotide","attrs":{"text":"BE404955","term_id":"9364423","term_text":"BE404955"}}BE404955, {"type":"entrez-nucleotide","attrs":{"text":"BE591127","term_id":"9846121","term_text":"BE591127"}}BE591127, {"type":"entrez-nucleotide","attrs":{"text":"BE637663","term_id":"9920774","term_text":"BE637663"}}BE637663, {"type":"entrez-nucleotide","attrs":{"text":"BF482781","term_id":"11566082","term_text":"BF482781"}}BF482781 and {"type":"entrez-nucleotide","attrs":{"text":"CD452422","term_id":"31367162","term_text":"CD452422"}}CD452422) were cloned, sequenced and compared. The results showed that the amplified polymorphic bands of P. huashanica and disomic addition line 2-1-6-3 shared 100% sequence identity, which was designated as the 7Ns disomic addition line. Disomic addition line 2-1-6-3 was evaluated to test the leaf rust resistance of adult stages in the field. We found that one pair of the 7Ns genome chromosomes carried new leaf rust resistance gene(s). Moreover, wheat line 2-1-6-3 had a superior numbers of florets and grains per spike, which were associated with the introgression of the paired P. huashanica chromosomes. These high levels of disease resistance and stable, excellent agronomic traits suggest that this line could be utilized as a novel donor in wheat breeding programs.     

Development and Molecular Cytogenetic Identification of a Novel Wheat–Leymus mollis Lm#7Ns (7D) Disomic Substitution Line with Stripe Rust Resistance

Leymus mollis (2n = 4x = 28, NsNsXmXm) possesses novel and important genes for resistance against multi-fungal diseases. The development of new wheat—L. mollis introgression lines is of great significance for wheat disease resistance breeding. M11003-3-1-15-8, a novel disomic substitution line of common wheat cv. 7182 –L. mollis, developed and selected from the BC₁F₅ progeny between wheat cv. 7182 and octoploid Tritileymus M47 (2n = 8x = 56, AABBDDNsNs), was characterized by morphological and cytogenetic identification, analysis of functional molecular markers, genomic in situ hybridization (GISH), sequential fluorescence in situ hybridization (FISH)—genomic in situ hybridization (GISH) and disease resistance evaluation. Cytological observations suggested that M11003-3-1-15-8 contained 42 chromosomes and formed 21 bivalents at meiotic metaphase I. The GISH investigations showed that line contained 40 wheat chromosomes and a pair of L. mollis chromosomes. EST-STS multiple loci markers and PLUG (PCR-based Landmark Unique Gene) markers confirmed that the introduced L. mollis chromosomes belonged to homoeologous group 7, it was designated as Lm#7Ns. While nulli-tetrasomic and sequential FISH-GISH analysis using the oligonucleotide Oligo-pSc119.2 and Oligo-pTa535 as probes revealed that the wheat 7D chromosomes were absent in M11003-3-1-15-8. Therefore, it was deduced that M11003-3-1-15-8 was a wheat–L. mollis Lm#7Ns (7D) disomic substitution line. Field disease resistance demonstrated that the introduced L. mollis chromosomes Lm#7Ns were responsible for the stripe rust resistance at the adult stage. Moreover, M11003-3-1-15-8 had a superior numbers of florets. The novel disomic substitution line M11003-3-1-15-8, could be exploited as an important genetic material in wheat resistance breeding programs and genetic resources.     

Chromosomal Localization of Genes Conferring Desirable Agronomic Traits from Wheat-Agropyron cristatum Disomic Addition Line 5113

Creation of wheat-alien disomic addition lines and localization of desirable genes on alien chromosomes are important for utilization of these genes in genetic improvement of common wheat. In this study, wheat-Agropyron cristatum derivative line 5113 was characterized by genomic in situ hybridization (GISH) and specific-locus amplified fragment sequencing (SLAF-seq), and was demonstrated to be a novel wheat-A. cristatum disomic 6P addition line. Compared with its parent Fukuhokomugi (Fukuho), 5113 displayed multiple elite agronomic traits, including higher uppermost internode/plant height ratio, larger flag leaf, longer spike length, elevated grain number per spike and spikelet number per spike, more kernel number in the middle spikelet, more fertile tiller number per plant, and enhanced resistance to powdery mildew and leaf rust. Genes conferring these elite traits were localized on the A. cristatum 6P chromosome by using SLAF-seq markers and biparental populations (F₁, BC₁F₁ and BC₁F₂ populations) produced from the crosses between Fukuho and 5113. Taken together, chromosomal localization of these desirable genes will facilitate transferring of high-yield and high-resistance genes from A. cristatum into common wheat, and serve as the foundation for the utilization of 5113 in wheat breeding.     

Molecular cytogenetic characterization of alien introgressions with gene Fhb3 for resistance to Fusarium head blight disease of wheat

Fusarium head blight (FHB) resistance was identified in the alien species Leymus racemosus, and wheat-Leymus introgression lines with FHB resistance were reported previously. Detailed molecular cytogenetic analysis of alien introgressions T01, T09, and T14 and the mapping of Fhb3, a new gene for FHB resistance, are reported here. The introgression line T09 had an unknown wheat-Leymus translocation chromosome. A total of 36 RFLP markers selected from the seven homoeologous groups of wheat were used to characterize T09 and determine the homoeologous relationship of the introgressed Leymus chromosome with wheat. Only short arm markers for group 7 detected Leymus-specific fragments in T09, whereas 7AS-specific RFLP fragments were missing. C-banding and genomic in situ hybridization results indicated that T09 has a compensating Robertsonian translocation T7AL·7Lr#1S involving the long arm of wheat chromosome 7A and the short arm of Leymus chromosome 7Lr#1 substituting for chromosome arm 7AS of wheat. Introgression lines T01 (2n = 44) and T14 (2n = 44) each had two pairs of independent translocation chromosomes. T01 had T4BS·4BL-7Lr#1S + T4BL-7Lr#1S·5Lr#1S. T14 had T6BS·6BL-7Lr#1S + T6BL·5Lr#1S. These translocations were recovered in the progeny of the irradiated line Lr#1 (T5Lr#1S·7Lr#1S). The three translocation lines, T01, T09, and T14, and the disomic addition 7Lr#1 were consistently resistant to FHB in greenhouse point-inoculation experiments, whereas the disomic addition 5Lr#1 was susceptible. The data indicated that at least one novel FHB resistance gene from Leymus, designated Fhb3, resides in the distal region of the short arm of chromosome 7Lr#1, because the resistant translocation lines share a common distal segment of 7Lr#1S. Three PCR-based markers, BE586744-STS, BE404728-STS, and BE586111-STS, specific for 7Lr#1S were developed to expedite marker-assisted selection in breeding programs.     

Mapping of novel powdery mildew resistance gene(s) from <Emphasis Type="Italic">Agropyron cristatum</Emphasis> chromosome 2P

Key message

A physical map of Agropyron cristatum 2P chromosome was constructed for the first time and the novel powdery mildew resistance gene(s) from chromosome 2P was(were) also mapped.

Abstract

Agropyron cristatum (L.) Gaertn. (2n = 28, PPPP), a wild relative of common wheat, is highly resistant to powdery mildew. Previous studies showed that wheat-A. cristatum 2P disomic addition line II-9-3 displayed high resistance to powdery mildew, and the resistance was attributable to A. cristatum chromosome 2P. To utilize and physically map the powdery mildew resistance gene(s), 15 wheat-A. cristatum 2P translocation lines and three A. cristatum 2P deletion lines with different chromosomal segment sizes, obtained from II-9-3 using ⁶⁰Co-γ ray irradiation, were characterized using cytogenetic and molecular marker analysis. A. cristatum 2P chromosomal segments in the translocations were translocated to different wheat chromosomes, including 1A, 4A, 5A, 6A, 7A, 1B, 2B, 3B, 7B, 3D, 4D, and 6D. A physical map of the 2P chromosome was constructed with 82 STS markers, consisting of nine bins with 34 markers on 2PS and eight bins with 48 markers on 2PL. The BC₁F₂ populations of seven wheat-A. cristatum 2P translocation lines (2PT-3, 2PT-4, 2PT-5, 2PT-6, 2PT-8, 2PT-9, and 2PT-10) were developed by self-pollination, tested with powdery mildew and genotyped with 2P-specific STS markers. From these results, the gene(s) conferring powdery mildew resistance was(were) located on 2PL bin FL 0.66–0.86 and 19 2P-specific markers were identified in this bin. Moreover, two new powdery mildew-resistant translocation lines (2PT-4 and 2PT-5) with small 2PL chromosome segments were obtained. The newly developed wheat lines with powdery mildew resistance and the closely linked molecular markers will be valuable for wheat disease breeding in the future.

     

Molecular Cytogenetic Characterization of a Wheat - Leymus mollis 3D（3Ns） Substitution Line with Resistance to Leaf Rust

Leymus mollis （Trin.） Pilger （NsNsXmXm, 2n = 28）, a wild relative of common wheat, possesses many potentially valuable traits that could be transferred to common wheat during breeding programs. In this study, the karyotypic constitution of a wheat - L. mollis 3D（3Ns#1） disomic substitution line isolated from the F5 progeny of octoploid Tritileymus M842-16 x Triticum durum cv. D4286, which was designated as 10DM57, was determined using genomic in situ hybridization （GISH）, fluorescent in situ hybridization （FISH）, SSR markers, and EST- STS markers. Screening of mitosis and meiosis showed that 10DM57 had a chromosome karyotype of 2n = 42 =21Ⅱ. GISH indicated that 10DM57 was a line with 40 chromosomes from wheat and two of the Ns chromosomes from L. mollis, which formed a ring bivalent in pollen mother cells at metaphase I. FISH analysis showed that the chromosome 3D may be replaced by 3Ns#1 in 10DM57. DNA markers, including SSR and EST-STS primers, showed that the pair of wheat chromosome 3D in 10DM57 was substituted by the pair of chromosome 3Ns#t from L. mollis. Evaluation of the agronomic traits showed that, compared with its common wheat relative 7182, 10DM57 was resistant to leaf rust while the spike length and number of spikes per plant were improved significantly, which correlated with a higher wheat yield. The new germplasm, 10DM57, could be exploited as an intermediate material in wheat genetic and breeding programs.     

Molecular Cytogenetic and Morphological Identification of a Wheat–<Emphasis Type="Italic">L. mollis</Emphasis> 1Ns(1D) Substitution Line,DM45

Leymus mollis (Trin.) Pilger (NsNsXmXm, 2n = 28), a wild relative of common wheat, possesses many potentially valuable traits for wheat breeding, i.e., strong and short stems, long spikes with numerous spikelets, tolerance to drought and cold, and resistance to many fungal and bacterial diseases. In this study, we hybridized a wheat–L. mollis triple substitution line 05DM6 × Triticum aestivum L. cv. 7182 to obtain DM45, a single chromosome substitution line. Cytological studies demonstrated that DM45 had a chromosome karyotype of 2n = 42 = 21II. Genomic in situ hybridization analysis indicated that DM45 had a pair of Ns chromosomes from L. mollis. Analysis with DNA markers, i.e., two simple sequence repeats (Xgdm111 and Xgdm126) and two expressed sequence tag-sequence tagged sites (CD453004 and BE443796), showed that the wheat 1Ds chromosome were substituted with a pair of 1Ns chromosomes from L. mollis in DM45. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested that DM45 possessed Ns genome-specific bands in the low and high molecular weight glutenin subunit regions, whereas it lacked one glutenin subunit translated from genes on chromosome 1D, thereby confirming that DM45 was a wheat–L. mollis 1Ns#1 (1D) disomic substitution line. Agronomic trait evaluations showed that DM45 was much improved in terms of the 1000-grain weight and the protein and glutenin contents of its seeds, as well as having more florets and spikelets compared with its relative, common wheat variety 7182. The substitution line DM45 could be used as a novel germplasm in wheat genetic and breeding programs.     

Molecular cytogenetic analysis of Leymus racemosus chromosomes added to wheat

Five disomic, two double-disomic, and two ditelosomic addition lines and one disomic substitution line derived from the crosses of Triticum aestivum (2n=6x=42, AABBDD)×Leymus racemosus (2n= 4x=28, JJNN) were identified by C-banding analysis. The homoeology of the added Leymus chromosomes was determined by RFLP analysis. Four of five disomic addition lines belonged to group 2, 5, 6 and 7 chromosomes of L. racemosus; these were designated as 2Lr?1(NAU516), 5Lr?1(NAU504, NAU514), 6Lr?1 (NAU512), and 7Lr?1(NAU501). Two additional chromosomes, 1Lr?1 and 3Lr?1, were present in double-disomic addition lines 1Lr?1+5Lr?1 (NAU525) and 3Lr?1+7Lr?1(NAU524), respec-tively. In the disomic substitution line wheat chromosome 2B was replaced by L. racemosus chromosome 2Lr?1 (NAU551). Two telocentric chromosomes, 2Lr?2S (NAU509) and 7Lr?1S (NAU511), were isolated as ditelosomic addition lines. The study presented here provides the first evidence of homoeology of the added L. racemosus chromosomes with wheat chromosomes using DNA markers. Our data provide the basis for further directed chromosome engineering aimed at producing compensating wheat-L. racemosus translocation lines.     

Novel Bread Wheat Lines Enriched in Carotenoids Carrying Hordeum chilense Chromosome Arms in the ph1b Background

The use of crop wild relative species to improve major crops performance is well established. Hordeum chilense has a high potential as a genetic donor to increase the carotenoid content of wheat. Crosses between the 7H^ch H. chilense substitution lines in wheat and the wheat pairing homoeologous1b (ph1b) mutant allowed the development of wheat-H. chilense translocation lines for both 7H^chα and 7H^chβ chromosome arms in the wheat background. These translocation lines were characterized by in situ hybridization and using molecular markers. In addition, reverse phase chromatography (HPLC) analysis was carried out to evaluate the carotenoid content and both 7H^chα∙7AL and 7AS∙7H^chβ disomic translocation lines. The carotenoid content in 7H^chα∙7AL and 7AS∙7H^chβ disomic translocation lines was higher than the wheat-7H^ch addition line and double amount of carotenoids than the wheat itself. A proteomic analysis confirmed that the presence of chromosome 7H^ch introgressions in wheat scarcely altered the proteomic profile of the wheat flour. The Psy1 (Phytoene Synthase1) gene, which is the first committed step in the carotenoid biosynthetic pathway, was also cytogenetically mapped on the 7H^chα chromosome arm. These new wheat-H. chilense translocation lines can be used as a powerful tool in wheat breeding programs to enrich the diet in bioactive compounds.     

小麦抗白粉病基因Pm21的分子鉴定和标记辅助选择

利用小麦抗白粉病基因Ｐｍ２１的ＲＡＰＤ标记、ＳＣＡＲ标记和荧光源位杂交技术对小麦抗病育种材料中的抗白粉病Ｐｍ２１基因进行了分子鉴定和标记辅助选择。     

Chromosomal Location and Comparative Genomics Analysis of Powdery Mildew Resistance Gene Pm51 in a Putative Wheat-Thinopyrum ponticum Introgression Line

Powdery mildew (PM) is a very destructive disease of wheat (Triticum aestivum L.). Wheat-Thinopyrum ponticum introgression line CH7086 was shown to possess powdery mildew resistance possibly originating from Th. ponticum. Genomic in situ hybridization and molecular characterization of the alien introgression failed to identify alien chromatin. To study the genetics of resistance, CH7086 was crossed with susceptible genotypes. Segregation in F₂ populations and F_2:3 lines tested with Chinese Bgt race E09 under controlled conditions indicated that CH7086 carries a single dominant gene for powdery mildew resistance. Fourteen SSR and EST-PCR markers linked with the locus were identified. The genetic distances between the locus and the two flanking markers were 1.5 and 3.2 cM, respectively. Based on the locations of the markers by nullisomic-tetrasomic and deletion lines of ‘Chinese Spring’, the resistance gene was located in deletion bin 2BL-0.89-1.00. Conserved orthologous marker analysis indicated that the genomic region flanking the resistance gene has a high level of collinearity to that of rice chromosome 4 and Brachypodium chromosome 5. Both resistance specificities and tests of allelism suggested the resistance gene in CH7086 was different from previously reported powdery mildew resistance genes on 2BL, and the gene was provisionally designated PmCH86. Molecular analysis of PmCH86 compared with other genes for resistance to Bgt in the 2BL-0.89-1.00 region suggested that PmCH86 may be a new PM resistance gene, and it was therefore designated as Pm51. The closely linked flanking markers could be useful in exploiting this putative wheat-Thinopyrum translocation line for rapid transfer of Pm51 to wheat breeding programs.     

Molecular mapping of stripe rust resistance gene <Emphasis Type="Italic">YrHu</Emphasis> derived from <Emphasis Type="Italic">Psathyrostachys huashanica</Emphasis>

Wheat stripe rust is a destructive disease that affects most wheat-growing areas worldwide. Resistance genes from related species and genera add to the genetic diversity available to wheat breeding programs. The stripe rust-resistant introgression line H9020-17-25-6-4 was developed from a cross of resistant Psathyrostachys huashanica with the susceptible wheat cultivar 7182. H9020-17-25-6-4 is resistant to all existing Chinese stripe rust races, including the three most widely virulent races, CYR32, CYR33, and V26. We attempted to characterize this new line by genomic in situ hybridization (GISH) and genetic analysis. GISH using P. huashanica genomic DNA as a probe indicated that the translocated segment was too small to be detected. Genetic analysis involving F₁, F₂, and F_2:3 materials derived from a cross of Mingxian 169 and H9020-17-25-6-4 indicated that a single dominant gene from H9020-17-25-6-4, temporarily designated YrHu, conferred resistance to CYR29 and CYR33. A genetic map consisting of four simple sequence repeat, two sequence-tagged site (STS), and two sequence-related amplified polymorphism markers was constructed. YrHu was located on the short arm of chromosome 3A and was about 0.7 and 1.5 cM proximal to EST-STS markers BG604577 and BE489244, respectively. Both the gene and the closely linked markers could be used in marker-assisted selection.     

Production and identification of wheat-Agropyron cristatum 6P translocation lines

The narrow genetic background of wheat is the primary factor that has restricted the improvement of crop yield in recent years. The kernel number per spike is the most important factor of the many potential characteristics that determine wheat yield. Agropyron cristatum (L.) Gaertn., a wild relative of wheat, has the characteristics of superior numbers of florets and kernels per spike, which are controlled by chromosome 6P. In this study, the wheat-A. cristatum disomic addition and substitution lines were used as bridge materials to produce wheat-A. cristatum 6P translocation lines induced by gametocidal chromosomes and irradiation. The results of genomic in situ hybridization showed that the frequency of translocation induced by gametocidal chromosomes was 5.08%, which was higher than the frequency of irradiated hybrids (2.78%) and irradiated pollen (2.12%). The fluorescence in situ hybridization results of the translocation lines showed that A. cristatum chromosome 6P could be translocated to wheat ABD genome, and the recombination frequency was A genome > B genome > D genome. The alien A. cristatum chromosome 6P was translocated to wheat homoeologous groups 1, 2, 3, 5 and 6. We obtained abundant translocation lines that possessed whole-arm, terminal, segmental and intercalary translocations. Three 6PS-specific and four 6PL-specific markers will be useful to rapidly identify and trace the translocated fragments. The different wheat-A. cristatum 6P translocation lines obtained in this study can provide basic materials for analyzing the alien genes carried by chromosome 6P. The translocation line WAT33-1-3 and introgression lines WAI37-2 and WAI41-1, which had significant characteristics of multikernel (high numbers of kernels per spike), could be utilized as novel germplasms for high-yield wheat breeding.