Octoploid Triticale Research Articles

Development and identification of two novel wheat-rye 6R derivative lines with adult-plant resistance to powdery mildew and high-yielding potential

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease that seriously threatens wheat yield and quality. To control this disease, host resistance is the most effective measure. Compared with the resistance genes from common wheat, alien resistance genes can better withstand infection of this highly variable pathogen. Development of elite alien germplasm resources with powdery mildew resistance and other key breeding traits is an attractive strategy in wheat breeding. In this study, three wheat-rye germplasm lines YT4-1, YT4-2, and YT4-3 were developed through hybridization between octoploid triticale and common wheat, out of which the lines YT4-1 and YT4-2 conferred adult-plant resistance (APR) to powdery mildew while the line YT4-3 was susceptible to powdery mildew during all of its growth stages. Using genomic in situ hybridization, multi-color fluorescence in situ hybridization, multi-color GISH, and molecular marker analysis, YT4-1, YT4-2, and YT4-3 were shown to be cytogenetically stable wheat-rye 6R addition and T1RS·1BL translocation line, 6RL ditelosomic addition and T1RS·1BL translocation line, and T1RS·1BL translocation line, respectively. Compared with previously reported wheat-rye derivative lines carrying chromosome 6R, YT4-1 and YT4-2 showed stable APR without undesirable pleiotropic effects on agronomic traits. Therefore, these novel wheat-rye 6R derivative lines are expected to be promising bridge resources in wheat disease breeding.

Development and molecular cytogenetic identification of a new wheat-rye 6RL ditelosomic addition and 1R (1B) substitution line with powdery mildew resistance

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a serious disease that critically threatens the yield and quality of wheat (Triticum aestivum L.). Using effective powdery mildew resistance genes is considered to be the optimal choice for controlling this disease. Against the background of high homogeneity among the modern commercial cultivars that are mainly derived from conventional interbreeding, the resistance genes from wheat relatives have especially prominent advantages. Octoploid triticale, produced by common wheat and rye (Secale cereale L.) through distant hybridization, is a new synthetic species and valuable gene donor for wheat improvement. In this study, we developed a wheat-rye line YT5 through the hybridization of octoploid triticale and two wheat lines. YT5 was confirmed to be a 6RL ditelosomic addition and 1R (1B) substitution line using genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization (mc-FISH), multicolor GISH (mc-GISH) and molecular marker analysis. Genetic analysis showed that the powdery mildew resistance in YT5 was derived from the rye chromosome arm 6RL. After inoculation with different Bgt isolates at the seedling stage, YT5 had compound reaction patterns with both obvious spores and hypersensitivity and gradually became highly resistant until the adult-plant stage, thus showing a resistance response significantly different from the reported Pm genes from rye chromosome 6RL. Meanwhile, YT5 showed promising agronomic performance and hence is expected to be an elite resistance donor for wheat improvement. To promote the transfer of the chromosome arm 6RL of YT5 in marker-assisted selection breeding, we selected and verified two 6RL-specific kompetitive allele-specific PCR markers that can be applied to efficiently detect this chromosome arm in different wheat backgrounds.

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Addition Line and Physical Localization of Its Powdery Mildew Resistance Gene

Rye (Secale cereale L.), a naturally cross-pollinating relative of wheat, is a tertiary gene donor and of substantial value in wheat improvement. Wheat powdery mildew is caused by Blumeria graminis f. sp. tritici (Bgt), which seriously affects yield and quality worldwide. Identifying and transferring new, effective resistance genes against powdery mildew from rye is important for wheat breeding. The current study developed a wheat-rye line YT2 resistant to powdery mildew by crossing, backcrossing, and self-pollination for multiple generations between octoploid triticale 09R2-100 and common wheat cultivar Shixin 616. YT2 was confirmed to be a 6R disomic addition and T1RS⋅1BL translocation line by genomic in situ hybridization (GISH), multicolor fluorescence in situ hybridization (mc-FISH), multicolor-GISH (mc-GISH), and molecular marker analyses. Disease responses to different Bgt isolates and genetic analysis showed that the powdery mildew resistance gene of YT2 was derived from the rye chromosome 6R of 09R2-100, which differed from the previously reported Pm genes from rye including Pm20 on 6RL. Resistance phenotype of different translocation lines and deletion lines derived from YT2 combined with newly developed 6RL-specific markers analysis suggested that the powdery mildew resistance gene of YT2 was localized to the region in chromosome 6RL: 890.09–967.51 Mb and flanked by markers XM189 and X4M19, corresponding to the reference genome of Weining rye. Therefore, YT2 could be used as a promising bridging parent for wheat disease resistance improvement.

Cytogenetic and molecular characteristics of rye genome in octoploid triticale (× Triticosecale Wittmack).

Alloploidization resulting from remote (interspecific or intergeneric) hybridization is one of the main factors in plant evolution, leading to the formation of new species. Triticale (× Triticosecale Wittmack, 1889) is the first artificial species created by crossing wheat (Triticum spp.) and rye (Secale cereale Linnaeus, 1753) and has a great potential as a grain and forage crop. Remote hybridization is a stress factor that causes a rapid reorganization of the parental genomes in hybrid progeny (“genomic shock”) and is accompanied by abnormalities in the chromosome set of hybrids. The formation of the hybrid genome and its subsequent stabilization are directly related to the normalization of meiosis and the correct chromosome segregation. The aim of this work was to cytogenetically characterize triticale (× Triticosecale rimpaui Wittmack, 1899, AABBDDRR) obtained by crossing Triticum aestivum Linnaeus, 1753. Triple Dirk D × Secale cereale L. Korotkostebel’naya 69 in F3–F6 generations of hybrids, and to trace the process of genetic stabilization of hybrid genomes. Also, a comparative analysis of the nucleotide sequences of the centromeric histone CENH3 genes was performed in wheat-rye allopolyploids of various ploidy as well as their parental forms. In the hybrid genomes of octoploid triticale an increased expression of the rye CENH3 variants was detected. The octoploid triticale plants contain complete chromosome sets of the parental subgenomes maintaining the chromosome balance and meiotic stability. For three generations the percentage of aneuploids in the progeny of such plants has been gradually decreasing, and they maintain a complete set of the paternal rye chromosomes. However, the emergence of hexaploid and new aneuploid plants in F5 and F6 generations indicates that stabilization of the hybrid genome is not complete yet. This conclusion was confirmed by the analysis of morphological features in hybrid plants: the progeny of one plant having the whole chromosome sets of parental subgenomes showed significant morphological variations in awn length and spike density. Thus, we expect that the results of our karyotyping of octoploid triticales obtained by crossing hexaploid wheat to diploid rye supplemented by comparative analysis of CENH3 sequences will be applicable to targeted breeding of stable octo- and hexaploid hybrids.

Characterization of a new hexaploid triticale 6D(6A) substitution line with increased grain weight and decreased spikelet number

Hexaploid triticale (×Triticosecale, AABBRR) is an important forage crop and a promising energy plant. Transferring D-genome chromosomes or segments from common wheat (Triticum aestivum) into hexaploid triticale is attractive in improving its economically important traits. Here, a hexaploid triticale 6D(6A) substitution line Lin 456 derived from the cross between the octoploid triticale line H400 and the hexaploid wheat Lin 56 was identified and analyzed by genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and molecular markers. The GISH analysis showed that Lin 456 is a hexaploid triticale with 14 rye (Secale cereale) chromosomes and 28 wheat chromosomes, whereas non-denaturing fluorescence in situ hybridization (ND-FISH) and molecular marker analysis revealed that it is a 6D(6A) substitution line. In contrast to previous studies, the signal of Oligo-pSc119.2 was observed at the distal end of 6DL in Lin 456. The wheat chromosome 6D was associated with increased grain weight and decreased spikelet number using the genotypic data combined with the phenotypes of the F2 population in the three environments. The thousand-grain weight and grain width in the substitution individuals were significantly higher than those in the non-substitution individuals in the F2 population across the three environments. We propose that the hexaploid triticale 6D(6A) substitution line Lin 456 can be a valuable and promising donor stock for genetic improvement during triticale breeding.

Genome-Wide Transcription During Early Wheat Meiosis Is Independent of Synapsis, Ploidy Level, and the Ph1 Locus.

Polyploidization is a fundamental process in plant evolution. One of the biggest challenges faced by a new polyploid is meiosis, particularly discriminating between multiple related chromosomes so that only homologous chromosomes synapse and recombine to ensure regular chromosome segregation and balanced gametes. Despite its large genome size, high DNA repetitive content and similarity between homoeologous chromosomes, hexaploid wheat completes meiosis in a shorter period than diploid species with a much smaller genome. Therefore, during wheat meiosis, mechanisms additional to the classical model based on DNA sequence homology, must facilitate more efficient homologous recognition. One such mechanism could involve exploitation of differences in chromosome structure between homologs and homoeologs at the onset of meiosis. In turn, these chromatin changes, can be expected to be linked to transcriptional gene activity. In this study, we present an extensive analysis of a large RNA-seq data derived from six different genotypes: wheat, wheat–rye hybrids and newly synthesized octoploid triticale, both in the presence and absence of the Ph1 locus. Plant material was collected at early prophase, at the transition leptotene-zygotene, when the telomere bouquet is forming and synapsis between homologs is beginning. The six genotypes exhibit different levels of synapsis and chromatin structure at this stage; therefore, recombination and consequently segregation, are also different. Unexpectedly, our study reveals that neither synapsis, whole genome duplication nor the absence of the Ph1 locus are associated with major changes in gene expression levels during early meiotic prophase. Overall wheat transcription at this meiotic stage is therefore highly resilient to such alterations, even in the presence of major chromatin structural changes. Further studies in wheat and other polyploid species will be required to reveal whether these observations are specific to wheat meiosis.

Assessing How the Aluminum-Resistance Traits in Wheat and Rye Transfer to Hexaploid and Octoploid Triticale.

The mechanisms of aluminum (Al) resistance in wheat and rye involve the release of citrate and malate anions from the root apices. Many of the genes controlling these processes have been identified and their responses to Al treatment described in detail. This study investigated how the major Al resistance traits of wheat and rye are transferred to triticale (x Tritosecale Wittmack) which is a hybrid between wheat and rye. We generated octoploid and hexaploid triticale lines and compared them with the parental lines for their relative resistance to Al, organic anion efflux and expression of some of the genes encoding the transporters involved. We report that the strong Al resistance of rye was incompletely transferred to octoploid and hexaploid triticale. The wheat and rye parents contributed to the Al-resistance of octoploid triticale but the phenotypes were not additive. The Al resistance genes of hexaploid wheat, TaALMT1, and TaMATE1B, were more successfully expressed in octoploid triticale than the Al resistance genes in rye tested, ScALMT1 and ScFRDL2. This study demonstrates that an important stress-tolerance trait derived from hexaploid wheat was expressed in octoploid triticale. Since most commercial triticale lines are largely hexaploid types it would be beneficial to develop techniques to generate genetically-stable octoploid triticale material. This would enable other useful traits that are present in hexaploid but not tetraploid wheat, to be transferred to triticale.

Reorganization of wheat and rye genomes in octoploid triticale (\xd7\xa0Triticosecale)

Main conclusionThe analysis of early generations of triticale showed numerous rearrangements of the genome. Complexed transformation included loss of chromosomes, t-heterochromatin content changes and the emergence of retrotransposons in new locations. This study investigated certain aspects of genomic transformations in the early generations (F5 and F8) of the primary octoploid triticale derived from the cross of hexaploid wheat with the diploid rye. Most of the plants tested were hypoploid; among eliminated chromosomes were rye chromosomes 4R and 5R and variable number of wheat chromosomes. Wheat chromosomes were eliminated to a higher extent. The lower content of telomeric heterochromatin was also found in rye chromosomes in comparison with parental rye. Studying the location of selected retrotransposons from Ty1-copia and Ty3-gypsy families using fluorescence in situ hybridization revealed additional locations of these retrotransposons that were not present in chromosomes of parental species. ISSR, IRAP and REMAP analyses showed significant changes at the level of specific DNA nucleotide sequences. In most cases, the disappearance of certain types of bands was observed, less frequently new types of bands appeared, not present in parental species. This demonstrates the scale of genome rearrangement and, above all, the elimination of wheat and rye sequences, largely due to the reduction of chromosome number. With regard to the proportion of wheat to rye genome, the rye genome was more affected by the changes, thus this study was focused more on the rye genome. Observations suggest that genome reorganization is not finished in the F5 generation but is still ongoing in the F8 generation.

High photosynthetic capability observed in the wheat germplasm with rye chromosomes

Improving photosynthetic capability is one of the most important factors for increasing wheat yield potential. The photosynthetic capability of wheat germplasm with different alien chromosomes was investigated and compared with bread wheat cultivars (BC) in this study, including wheat addition lines (CA), hexaploid triticale (HT), octoploid triticale (OT), and synthetic hexaploid wheat lines (SHW). Results indicated that HT, OT, and SHW produced significantly higher biomass plant−1(BMPP), with HT displaying the highest grain yield plant−1 (GYPP). Distinct superiority of net photosynthetic rate (Pn) and carboxylation activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was observed in HT and OT. Meanwhile, OT showed the highest expression of the Rubisco large subunit gene (rbcL) in the flag leaves at heading and grain-filling stages, though the coding region of rbcL was highly conserved in all investigated materials. Further analysis indicated that OT and Chinese Spring-rye disomic addition lines displayed higher expression of Rubisco small subunit gene (rbcS). Correlation analysis revealed significant and positive correlations between Pn and the expressions of rbcL (at both heading and grain-filling stages), the expression of rbcS (at heading stage), and the carboxylation activity of Rubisco (at grain-filling stage). Anatomical structure analysis of the chloroplasts showed SHW with longer chloroplasts and more chloroplast grana and grana lamella. In the present study, HT, OT, and Chinese Spring-rye disomic addition lines with rye chromosomes displayed greater photosynthetic capability than BC and SHW, and could be applied in breeding programs to improve the photosynthetic efficiency of wheat.

Divergent Development of Hexaploid Triticale by a Wheat - Rye -Psathyrostachys huashanica Trigeneric Hybrid Method.

Hexaploid triticale is an important forage crop and a promising energy plant. Some forms were previously reported for developing the hexaploid triticale, such as crossing tetraploid wheat or hexaploid wheat with rye, crossing hexaploid triticale and/or hexaploid wheat with octoploid triticale, and spontaneously appearing in the selfed progenies of octoploid triticale. In the present study, we developed an effective method for production of diverse types of hexaploid triticale via wheat—rye—Psathyrostachys huashanica trigeneric hybrid. Genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) karyotyping revealed that D genome chromosomes were completely eliminated and the whole A, B, and R genome chromosomes were retained in three lines. More interestingly, the composite genome of the line K14-489-2 consisted of complete A and B genomes and chromosomes 1D, 2R, 3R, 4R, 5R, 6R, and 7R, that of line K14-491-2 was 12 A-genome (1A-6A), 14 B-genome (1B-7B), 12 R-genome (1R-3R, 5R-7R), and chromosomes 1D and 3D, and that of the line K14-547-1 had 26A/B and 14R chromosomes, plus one pair of centric 6BL/2DS translocations. This finding implies that some of D genome chromosomes can be spontaneously and stably incorporated into the hexaploid triticale. Additionally, a variety of high-molecular-weight glutenin subunits (HMW-GS) compositions were detected in the six hexaploid triticale lines, respectively. Besides, compared with its recurrent triticale parent Zhongsi828, these lines showed high level of resistance to stripe rust (Puccinia striiformis f. sp. tritici, Pst) pathogens prevalent in China, including V26/Gui 22. These new hexaploid triticales not only enhanced diversification of triticale but also could be utilized as valuable germplasm for wheat improvement.

Chromosome aberrations induced by zebularine in triticale.

Chromosome engineering is an important approach for generating wheat germplasm. Efficient development of chromosome aberrations will facilitate the introgression and application of alien genes in wheat. In this study, zebularine, a DNA methylation transferase inhibitor, was successfully used to induce chromosome aberrations in the octoploid triticale cultivar Jinghui#1. Dry seeds were soaked in zebularine solutions (250, 500, and 750 μmol/L) for 24 h, and the 500 μmol/L treatment was tested in three additional treatment times, i.e., 12, 36, and 48 h. All treatments induced aberrations involving wheat and rye chromosomes. Of the 920 cells observed in 67 M1 plants, 340 (37.0%) carried 817 aberrations with an average of 0.89 aberrations per cell (range: 0-12). The aberrations included probable deletions, telosomes and acentric fragments (49.0%), large segmental translocations (28.9%), small segmental translocations (17.1%), intercalary translocations (2.6%), long chromosomes that could carry more than one centromere (2.0%), and ring chromosomes (0.5%). Of 510 M2 plants analyzed, 110 (21.6%) were found to carry stable aberrations. Such aberrations included 79 with varied rye chromosome numbers, 7 with wheat and rye chromosome translocations, 15 with possible rye telosomes/deletions, and 9 with complex aberrations involving variation in rye chromosome number and wheat-rye translocations. These indicated that aberrations induced by zebularine can be steadily transmitted, suggesting that zebularine is a new efficient agent for chromosome manipulation.

Application of ISSR-PCR, IRAP-PCR, REMAP-PCR, and ITAP-PCR in the assessment of genomic changes in the early generation of triticale

Analysis of structural changes of octoploid triticale genomes was conducted in F2 and F3 generations. The plants were derived from crosses of five cultivars and breeding lines of hexaploid wheat (Triticum aestivum L.) with one cultivar of rye (Secale cereale L). The study used four marker systems: inter-simple sequence repeat (ISSR), inter-retrotransposon amplified polymorphism (IRAP), retrotransposon-microsatellite amplified polymorphism (REMAP), and a technique named inter-transposon amplified polymorphism (ITAP) developed by the authors. Most frequently, elimination of specific bands was observed, especially of rye bands. Depending on the cross combination, the percentage of eliminated rye bands ranged from 73.6 to 80.6 %. A lower percentage of wheat bands was eliminated, i.e., from 57.6 to 76.48 %, depending on the combination of crosses. The emergence of new types of bands in hybrids absent in the parental forms was the rarest phenomenon (14.5–17.9 %). The results indicate the ongoing process of genome rearrangements at the molecular level in the early generations of plant crosses that also involve repeated nucleotide sequences of DNA.

Identification of the 1RS-7DS.7DL wheat-rye small segment translocation lines

Rye (Secale cereale L., RR) is a valuable genetic resource for the improvement of common wheat (Triticum aestivum L., AABBDD). Transferring alien rye genes into wheat by distant hybridization and automatic chromosome doubling is an important and efficient method to boost agronomic traits, disease resistance and widening the gene pool in wheat. In this study, an octoploid triticale CD-13 (AABBDDRR) was obtained via automatic chromosome doubling by crossing landrace Penganbaimaizi (T. aestivum L., AABBDD) and rye "Qinling rye" (S. cereale cv. Qinling, RR). GISH and FISH analyses indicated that CD-13 contained a 1RS-7DS.7DL wheat-rye small segment translocation chromosome. In order to transfer the 1RS-7DS small segment translocation into hexaploid wheat, 58 lines of the F5 inbred population from the cross CD-13 x Chuanmai 42 were screened for rye chromosome segments by GISH and FISH analyses. The results showed that 13 lines contained the 1RS-7DS.7DL small segment translocation chromosome by reciprocal translocation between 1RS and 7DS. These translocation lines carrying 1RS small rye alien segment were tested for the translocation breakpoints and the presence of a storage protein locus Sec-1. The Sec-1 locus was absent in the line 811, a stable 1RS-7DS.7DL small segment translocation line. The translocation breakpoint of 1RS-7DS.7DL of this line was located in the interval of IB267-IAG95 around the telomere of 1RS chromosome. Thousand-kernel weight of the line 811 was much higher than the parent CD-13, but not significantly different from Chuanmai 42. This indicated that 1RS-7DS.7DL small segment translocation had no negative effect on thousand-kernel weight in the genetic background of Chuanmai 42. The line with 1RS-7DS.7DL translocation chromosomes can be used as a new genetic material for further studies of valuable genes and their genetic effect on 1RS small segment.

Mapping a new secalin locus on the rye 1RS arm

A gene designated Sec-N encoding secalin was mapped in the introgressive winter common wheat line Hostianum 273/97 (H273) with the wheat-rye substitution (1B)1R from the octoploid triticale AD825. F2 seeds from crossing the line H273 with the line Hostianum 242/97-2 carrying the wheat-rye 1BL/1RS translocation were analysed. The studied component on the SDS-electrophoregram of total proteins was revealed to be a monomeric secalin which is encoded by the gene at the new locus Sec-N located distally with respect to the Sec-1 locus at a distance of 21.4 +/- 2.5% (22.9 +/- 3.1 cM). The arrangement of the secalin loci on the 1RS arm indicates that the Sec-N locus is to be homoeologous to the Gli-1 loci of common wheat.

Abnormal mitosis induced by wheat–rye 1R monosomic addition lines

Octoploid triticale were derived from common wheat (Triticum aestivum L. 'Mianyang11') × rye (Secale cereale L. 'Kustro'), and some progeny were obtained by the backcrossing of triticale with 'Mianyang11' followed by self-fertilization. In situ hybridization using rye genomic DNA and repetitive sequences pAs1 and pSc119.2 as probes was used to analyze the mitotic chromosomes of these progeny. Three wheat-rye 1R monosomic addition lines and a wheat line (12FT-1685) containing a 1R and a 1BL.1RS translocation chromosome were identified. Abnormal mitosis was observed in the two lines. During mitosis of a 1R monosomic addition line (3-8-20-1R-2), lagging chromosomes, micronuclei, chromosomal bridges, and the one pole segregation of 1R chromosome were observed. Abnormal mitotic behaviour of chromosomes was also observed in some of the self-progeny plants of lines 12FT-1685 and 3-8-20-1R-2. These progeny contained 1R chromosome or 1R chromosome arm. In addition, 4B chromosomes were absent from one of the progeny of 3-8-20-1R-2. This abnormal mitotic behaviour of chromosomes was not observed in two other 1R monosomic addition lines. These results indicate that a single 1R chromosome added to wheat might cause abnormal mitotic behaviour of both wheat and rye chromosomes and different genetic variations might occurr among the sibling 1R monosomic addition lines.

Production of hexaploid triticale by a synthetic hexaploid wheat-rye hybrid method

Hexaploid triticale, including its primary and secondary forms, is an important forage crop and a promising energy plant. Primary forms are usually developed by crossing Triticum turgidum L. with rye, with secondary forms obtained by crossing primary hexaploid triticale and/or hexaploid wheat with octoploid triticale. In this study, we developed an effective method for production of hexaploid triticale via hybridization of synthetic hexaploid wheat (SHW) with rye. The three employed SHW lines were derived from hybridization of T. turgidum with Aegilops tauschii Cosson, and inherited meiotic restitution genes, which can promote the formation of functional gametes in haploid status, from their T. turgidum parents. Although the resulting tetraploid F-1 hybrids with rye (genome ABDR) produced amphiploids (octoploid triticale) and partial amphiploids, the final hybrid products obtained through fertility selection over several generations were hexaploids. These hexaploids were the result of preferential elimination of D-genome chromosomes. In addition to complete hexaploid triticale with 28 intact A/B and 14 intact R chromosomes, we obtained hexaploid triticales with other chromosome constitutions, including monosomic, substitution, and translocation lines. Chromosomes 2D and 5D from the wild species A. tauschii were incorporated into the hexaploid triticales. Out of eight analyzed stable lines derived from three different SHW-L1/rye F-1 plants, we observed four lines with small-fragment translocations between wheat and rye chromosomes. Rapid production of hexaploid triticales using this method involves two factors: (1) hybridization between hexaploid wheat with a meiotic restitution gene(s) and rye and (2) selection for good fertility during F-3 and subsequent generations.

Establishment of wheat-rye addition lines and <I>De Novo</I> powdery mildew resistance gene from chromosome 5R

The F5 plants derived from octoploid triticale × common wheat were investigated by FISH methods using repetitive DNA sequences pAS1 and pSc119.2 as probes. The disease resistance of these plants was also screened and evaluated in the field. The 1R, 2R, 3R, 4R, 5R, 6R and 7R monosomic addition lines and 1R and 2R disomic addition lines were found. The occurrence frequencies of chromosomes 1R and 4R addition lines were higher than that of chromosomes 2R, 3R, 5R, 6R, and 7R addition lines in the high generation screened. The 5R and 6R monosomic addition lines were immune to powdery mildew. The chromosome 5R in this study might carry new powdery mildew resistance gene(s). In addition, the preferential elimination of chromosome 4B was observed in several plants.

Identification of 1BL·1RS Wheat-Rye Chromosome Translocations via 1RS Specific Molecular Markers and Genomic in situ Hybridization

Sixty-five rye-specific molecular markers were validated with two 1BL·1RS wheat-rye chromosome translocations(Kavkaz and Shannong 030-1),one 1AL·1RS wheat-rye chromosome translocation(Amigo),Jingzhouheimai,octoploid Triticale Jinsong 49,1R-7R addition lines,Chinese Spring,Huixianhong,Mingxian 169,and Chancellor.Eleven markers were selected due to stable amplification,clear PCR products in electrophoresis gels,and good repeatability,of which eight markers,i.e.,NOR-1,SECA2/SECA3,SCSS30.2,Sec1Gene,Sec1Pro,ω-Sec-P1/P2,ω-Sec-P3/P4,and IB-267 amplified specific bands associated with 1AL·1RS and 1BL·1RS translocations.Another three markers,O-SEC5'-A/O-SEC3'-R,IAG95-1,and SCM-9,were able to discriminate wheat-rye translocations involving different sources of 1RS.Both molecular markers and genomic in situ hybridization were used to detect the frequency of 1BL·1RS translocations in forty Shandong varieties(lines)bred in recent years.Among the forty varieties(lines),only 15%(Weimai 8,Lumai 14,Jining 13,Shannong 664,Shannongyoumai 3,and Yannong 25)harbored the 1BL·1RS translocation with the whole short arm of chromosome 1R of rye,and no 1AL·1RS or other translocation types were found.

Submicroscopic Morphology Comparisons between Hybrid F1 by Wheat and Octoploid Triticale and the Parental Generation

F1 hybrid generation comes from the hybridization of common wheat Jingdong 8 as the female parent and octoploid triticale Jinsong 5 as the male parent. It can be clearly seen from the submicroscopic morphology comparisons of pollen grains, leaf epidermis and stomas between hybrid F1 and the parents that most of the shapes of the parents’ pollen grains are nearly circular, while those of the F1 hybrid pollen grains are irregular and severely wizened. In addition, the pollen grains of the F1 hybrid and parents are significantly different in the submicroscopic features of exine sculptures and germ pores. The common features of the three tested materials are stomatal apparatus, long cell and hair cell, and the cells are arranged in parallel with the vein. Leaf epidermal cells of the female parent which is the common wheat are clear outline, and they are also arranged tidily and smoothly, Pores are arranged in a straight line. Guard cells are dumbbell-shaped with bristles of different lengths. Pores of the male parent which is octoploid triticale have ridge-like heaves with horizontal and vertical alignment around them, and they are rectangular and large, also the general arrangement type is linear. Guard cells is very obvious, but with very few and short bristles. Both of the submicroscopic morphologies of leaf epidermises and stomas of the hybrid F1 are more similar with those of the male parent, while the leaf epidermises have bristles and the size of pores ranges between the two parents. The F1 hybrids and parents are significantly different in submicroscopic morphologies on pollens, leaf epidermises and stomas, so that the distinctions of submicroscopic morphologies can be used as a basis in the indicators and identification of the distant hybrids and their parents.

Characterization of ω-secalin genes from rye, triticale, and a wheat 1BL/1RS translocation line

Sixty-two DNA sequences for the coding regions of omega-secalin (ω-secalin) genes have been characterized from rye (Secale cereale L.), hexaploid and octoploid triticale (× Triticosecale Wittmack), and wheat (Triticum aestivum L.) 1BL/1RS translocation line. Only 19 out of the 62 ω-secalin gene sequences were full-length open reading frames (ORFs), which can be expressed into functional proteins. The other 43 DNA sequences were pseudogenes, as their ORFs were interrupted by one or a few stop codons or frameshift mutations. The 19 ω-secalin genes have a typical primary structure, which is different from wheat gliadins. There was no cysteine residue in ω-secalin proteins, and the potential celiac disease (CD) toxic epitope (PQQP) was identified to appear frequently in the repetitive domains. The ω-secalin genes from various cereal species shared high homology in their gene sequences. The ω-secalin gene family has involved fewer variations after the integration of the rye R chromosome or whole genome into the wheat or triticale genome. The higher Ka/Ks ratio (i.e. non-synonymous to synonymous substitutions per site) in ω-secalin pseudogenes than in ω-secalin ORFs indicate that the pseudogenes may be subject to a reduced selection pressure. Based on the conserved sequences of ω-secalin genes, it will be possible to manipulate the expression of this gene family in rye, triticale, or wheat 1BL/1RS translocation lines, to reduce its negative effects on grain quality.