Rye Chromosome Research Articles

Physical Location of New Stripe Rust Resistance Gene(s) and PCR-Based Markers on Rye (Secale cereale L.) Chromosome 5 Using 5R Dissection Lines

The rye (Secale cereale L.) 5R chromosome contains some elite genes that can be used to improve wheat cultivars. In this study, a set of 5RKu dissection lines was obtained, and 111 new PCR-based and 5RKu-specific markers were developed using the specific length amplified fragment sequencing (SLAF-seq) method. The 111 markers were combined with the 52 5RKu-specific markers previously reported, and 65 S. cereale Lo7 scaffolds were physically mapped to six regions of the 5RKu chromosome using the 5RKu dissection lines. Additionally, the 5RLKu arm carried stripe rust resistance gene(s) and it was located to the region L2, the same region where 22 5RKu-specific markers and 11 S. cereale Lo7 scaffolds were mapped. The stripe rust resistance gene(s) located in the 5RLKu arm might be new one(s) because its source and location are different from the previously reported ones, and it enriches the resistance source of stripe rust for wheat breeding programs. The markers and the S. cereale Lo7 scaffolds that were mapped to the six regions of the 5RKu chromosome can facilitate the utilization of elite genes on the 5R chromosome in the improvement of wheat cultivars.

Nuclear Disposition of Alien Chromosome Introgressions into Wheat and Rye Using 3D-FISH.

During interphase, the chromosomes of eukaryotes decondense and they occupy distinct regions of the nucleus, called chromosome domains or chromosome territories (CTs). In plants, the Rabl’s configuration, with telomeres at one pole of nucleus and centromeres at the other, appears to be common, at least in plants with large genomes. It is unclear whether individual chromosomes of plants adopt defined, genetically determined addresses within the nucleus, as is the case in mammals. In this study, the nuclear disposition of alien rye and barley chromosomes and chromosome arm introgressions into wheat while using 3D-FISH in various somatic tissues was analyzed. All of the introgressed chromosomes showed Rabl’s orientation, but their relative positions in the nuclei were less clear. While in most cases pairs of introgressed chromosomes occupied discrete positions, their association (proximity) along their entire lengths was rare, and partial association only marginally more frequent. This arrangement is relatively stable in various tissues and during various stages of the cell cycle. On the other hand, the length of a chromosome arm appears to play a role in its positioning in a nucleus: shorter chromosomes or chromosome arms tend to be located closer to the centre of the nucleus, while longer arms are more often positioned at the nuclear periphery.

Ultrastructure and Dynamics of Synaptonemal Complex Components During Meiotic Pairing and Synapsis of Standard (A) and Accessory (B) Rye Chromosomes.

During prophase I a meiosis-specific proteinaceous tripartite structure, the synaptonemal complex (SC), forms a scaffold to connect homologous chromosomes along their lengths. This process, called synapsis, is required in most organisms to promote recombination between homologs facilitating genetic variability and correct chromosome segregations during anaphase I. Recent studies in various organisms ranging from yeast to mammals identified several proteins involved in SC formation. However, the process of SC disassembly remains largely enigmatic. In this study we determined the structural changes during SC formation and disassembly in rye meiocytes containing accessory (B) chromosomes. The use of electron and super-resolution microscopy (3D-SIM) combined with immunohistochemistry and FISH allowed us to monitor the structural changes during prophase I. Visualization of the proteins ASY1, ZYP1, NSE4A, and HEI10 revealed an extensive SC remodeling during prophase I. The ultrastructural investigations of the dynamics of these four proteins showed that the SC disassembly is accompanied by the retraction of the lateral and axial elements from the central region of the SC. In addition, SC fragmentation and the formation of ball-like SC structures occur at late diakinesis. Moreover, we show that the SC composition of rye B chromosomes does not differ from that of the standard (A) chromosome complement. Our ultrastructural investigations indicate that the dynamic behavior of the studied proteins is involved in SC formation and synapsis. In addition, they fulfill also functions during desynapsis and chromosome condensation to realize proper recombination and homolog separation. We propose a model for the homologous chromosome behavior during prophase I based on the observed dynamics of ASY1, ZYP1, NSE4A, and HEI10.

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.

Instability of Alien Chromosome Introgressions in Wheat Associated with Improper Positioning in the Nucleus.

Alien introgressions introduce beneficial alleles into existing crops and hence, are widely used in plant breeding. Generally, introgressed alien chromosomes show reduced meiotic pairing relative to the host genome, and may be eliminated over generations. Reduced pairing appears to result from a failure of some telomeres of alien chromosomes to incorporate into the leptotene bouquet at the onset of meiosis, thereby preventing chiasmate pairing. In this study, we analysed somatic nuclei of rye introgressions in wheat using 3D-FISH and found that while introgressed rye chromosomes or chromosome arms occupied discrete positions in the Rabl’s orientation similar to chromosomes of the wheat host, their telomeres frequently occupied positions away from the nuclear periphery. The frequencies of such abnormal telomere positioning were similar to the frequencies of out-of-bouquet telomere positioning at leptotene, and of pairing failure at metaphase I. This study indicates that improper positioning of alien chromosomes that leads to reduced pairing is not a strictly meiotic event but rather a consequence of a more systemic problem. Improper positioning in the nuclei probably impacts the ability of introgressed chromosomes to migrate into the telomere bouquet at the onset of meiosis, preventing synapsis and chiasma establishment, and leading to their gradual elimination over generations.

Persistence of rye (Secale cereale L.) chromosome arm 1RS in wheat (Triticum aestivum L.) breeding programs of the Great Plains of North America

Rye (Secale cereale L.) chromosome arm 1RS has been used world-wide by wheat (Triticum aestivum L.) breeding programs as a source of pest- and pathogen-resistance genes, and to improve grain yield and stress tolerance. The most common vehicles used to access 1RS are various 1AL.1RS and 1BL.1RS wheat-rye chromosomal translocations. Over the past 25 years, advanced North American wheat breeding lines were evaluated, first by assay of secalin storage proteins, and later by use of DNA marker TSM0120, for the presence of these two translocations. Both methods provide accurate and efficient means of identifying and differentiating 1BL.1RS and 1A.1RS. Both 1Al.1RS and 1BL.1RS wheats were found in all tested years. 1AL.1RS lines were more common in southern Great Plains breeding programs. 1AL.1RS lines were released as cultivars at a frequency identical to that of wild-type breeding lines. In contrast, 1BL.1RS breeding lines were developed by breeding programs throughout the Great Plains, but fewer were released as cultivars. Both 1RS translocation types persist in Great Plains breeding programs. The lower rate of release of 1BL.1RS cultivars no doubt is a consequence of the more drastic effects on breadmaking quality relative to those observed with 1AL.1RS.

Polymorphism in the short arm of 1R rye chromosomes in wheat lines with 1RS.1BL translocation and 1R(1B) substitution from different sources

Aim. The short arm of 1R rye (Secale cereale L.) chromosome is widely used in the breeding of bread wheat (Triticum aestivum L.), in particular 1RS.1BL, to introsgress genes of resistance to leaf (Lr26), stem (Sr31), striped (Yr9) rusts, as well as powdery mildew (Pm8); 1RS.1AL carries Gb2/Gb6 resistance genes to the wheat aphid (Schizaphis graminum Rondani), powdery mildew (Pm17), and the Cmc4 resistance gene to the Aceria tosichella Koifer mite, which is a vector for spreading of wheat mosaic virus. The aim of the research is to reveal molecular genetic polymorphisms of short arm rye 1RS chromosomes of different origins in bread wheat lines with 1RS.1BL translocation or 1R(1B) substitution from different sources. Methods. Genetic polymorphism of lines was analyzed by using PCR with a number of rye and wheat microsatellite markers. Results. It was shown that the CWXs line has a recombinant 1RS arm that contains the chromosomes parts of 1RS of the parental lines H242/97-2 and H273/97, due to crossover event, which led to the recombination of marked loci. Conclusions. Molecular genetic polymorphism has been reviled in 1RS.1BL translocations and 1R substituted rye chromosomes of different origins in H242/97-2, CWXs, H273/97, PavonMA1, Salmon lines, as there are different alleles present at loci: Xscm9, Xtsm422, Xgwm752, Xgwm18, Taglgap. Keywords: polymorphism, 1RS.1BL translocation, PCR analysis, microsatellites markers.

Using the 6RLKu Minichromosome of Rye (Secale cereale L.) to Create Wheat-Rye 6D/6RLKu Small Segment Translocation Lines with Powdery Mildew Resistance.

Long arms of rye (Secale cereale L.) chromosome 6 (6RL) carry powdery mildew resistance genes. However, these sources of resistance have not yet been successfully used in commercial wheat cultivars. The development of small segment translocation chromosomes carrying resistance may result in lines carrying the 6R chromosome becoming more commercially acceptable. However, no wheat-rye 6RL small segment translocation line with powdery mildew resistance has been reported. In this study, a wheat-rye 6RLKu minichromosome addition line with powdery mildew resistance was identified, and this minichromosome was derived from the segment between L2.5 and L2.8 of the 6RLKu chromosome arm. Following irradiation, the 6RLKu minichromosome divided into two smaller segments, named 6RLKumi200 and 6RLKumi119, and these fragments participated in the formation of wheat-rye small segment translocation chromosomes 6DS/6RLKumi200 and 6DL/6RLKumi119, respectively. The powdery mildew resistance gene was found to be located on the 6RLKumi119 segment. Sixteen 6RLKumi119-specific markers were developed, and their products were cloned and sequenced. Nucleotide BLAST searches indicated that 14 of the 16 sequences had 91–100% similarity with nine scaffolds derived from 6R chromosome of S. cereale L. Lo7. The small segment translocation chromosome 6DL/6RLKumi119 makes the practical utilization in agriculture of powdery mildew resistance gene on 6RLKu more likely. The nine scaffolds are useful for further studying the structure and function of this small segment.

Out-of-position telomeres in meiotic leptotene appear responsible for chiasmate pairing in an inversion heterozygote in wheat (Triticum aestivum L.).

Chromosome pairing in meiosis usually starts in the vicinity of the telomere attachment to the nuclear membrane and congregation of telomeres in the leptotene bouquet is believed responsible for bringing homologue pairs together. In a heterozygote for an inversion of a rye (Secale cereale L.) chromosome arm in wheat, a distal segment of the normal homologue is capable of chiasmate pairing with its counterpart in the inverted arm, located near the centromere. Using 3D imaging confocal microscopy, we observed that some telomeres failed to be incorporated into the bouquet and occupied various positions throughout the entire volume of the nucleus, including the centromere pole. Rye telomeres appeared ca. 21 times more likely to fail to be included in the telomere bouquet than wheat telomeres. The frequency of the out-of-bouquet rye telomere position in leptotene was virtually identical to the frequency of telomeres deviating from Rabl's orientation in the nuclei of somatic cells, and was similar to the frequency of synapsis of the normal and inverted chromosome arms, but lower than the MI pairing frequency of segments of these two arms normally positioned across the volume of the nucleus. Out-of-position placement of the rye telomeres may be responsible for reduced MI pairing of rye chromosomes in hybrids with wheat and their disproportionate contribution to aneuploidy, but appears responsible for initiating chiasmate pairing of distantly positioned segments of homology in an inversion heterozygote.

Development and Characterization of Wheat-Rye Hybrids Produced by Meiotic Restitution

The nature of the formation of fertile progenies of F2 and F3 generations of wheat–rye hybrids obtained as a result of meiotic restitution using the Saratovskaya 29 variety (C29 x R) and the wheat–rye substituted line 1Rv(1A) (1Rv (1A) × R) was studied. The karyotype analysis of the F2Triticum aestivum L. cv. Saratovskaya 29 × Secale cereale L. var. Onochoyskaya (S29 × R) hybrid using C-banding revealed 56 chromosomes; among them were 42 wheat chromosomes and 14 rye chromosomes. The karyotype of the F2 1Rv(1A) × R hybrid contained 46 chromosomes, of which three pairs of rye chromosomes 1R1R4R4R2RL2RL, 1R1R replaced the chromosomes 1A1A, and 2RL2RL and 4R4R were additional to the wheat chromosomes. In the F3 generation of S29 × R hybrids, the octoploid number of chromosomes with aneuploidy of single rye and wheat chromosomes was preserved, while in the 1Rv(1A) × R hybrids the number of chromosomes varied from 42 to 49, but in most plants 2n = 46 was retained. Meiosis of the F3 1Rv(1A) × R hybrids was more stable than that of the S29 × R hybrids. The average number of univalents in 1Rv(1A) × R hybrids was 1.54 ± 0.17, which was significantly lower than in S29 × R hybrid progenies (2.56 ± 0.23 and 2.07 ± 0.27). The F3 С29 × R and 1Rv(1A) × R hybrids were characterized by the variability in the seed set and 1000-grain weight. On average, С29 × R plants produced a smaller number of grains with but larger size than 1Rv(1A) × R plants, forming more grains with lower 1000-grain weight. The obtained results indicate the influence of the substitution 1Rv(1A) on the reorganization of hybrid genomes.

Development and molecular cytogenetic identification of a new wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust and sharp eyespot.

A wheat-rye 4R chromosome disomic addition line with resistances to powdery mildew, stripe rust, sharp eyespot and high kernel number per spike was developed and characterized by molecular cytogenetic method as novel resistant germplasm. Rye (Secale cereale L.), a close relative of common wheat, is an important and valuable gene donor with multiple disease resistance for wheat improvement. However, resistance genes derived from rye have successively lost resistance to pathogens due to the coevolution of pathogen virulence and host resistance. Development and identification of new effective resistance gene sources from rye therefore are of special importance and urgency. In the present study, a wheat-rye line WR35 was produced through distant hybridization, embryo rescue culture, chromosome doubling and backcrossing. WR35 was then proven to be a new wheat-rye 4R disomic addition line using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization) and ND-FISH (non-denaturing FISH) with multiple probes, mc-GISH (multicolor GISH), rye chromosome arm-specific marker analysis and SLAF-seq (specific-locus amplified fragmentsequencing) analysis. At the adult stage, WR35 exhibited high levels of resistance to the powdery mildew (Blumeria graminis f. sp. tritici, Bgt) and stripe rust (Puccinia striiformis f. sp. tritici, Pst) pathogens prevalent in China, and a highly virulent isolate of Rhizoctonia cerealis, the cause of wheat sharp eyespot. At the seedling stage, it was highly resistant to 22 of 23 Bgt isolates and four Pst races. Based on its disease responses to different pathogen isolates, WR35 may possess resistance gene(s) for powdery mildew, stripe rust and sharp eyespot, which differed from the known resistance genes from rye. In addition, WR35 was cytologically stable and produced high kernel number per spike. Therefore, WR35 with multi-disease resistances and desirable agronomic traits should serve as a promising bridging parent for wheat chromosome engineering breeding.

Correlations at the interspecific and intraspecific hybrids of winter triticale

The main abiotic factor affecting the yield of triticale is the  GTK for the vegetation period (r = 0.93 ± ** 0.0193). Positive influence is ensured by precipitation before sowing (r = 0,37 ... 0,71 **). Partial death of plants during the sowing period (r = -0.37 ± 0.1233) and at the beginning of vegetation (r = -0.51 ± * 0.1057) occurs from excess moisture during these periods. During the growing season, high temperatures (r = -0.39 ... -0.71 **) and excess moisture (r = -0.32 ... -0.63 *) reduce yields. Presence in samples of telocentric chromosomes of wheat and rye, splitting testify to the continuing formative process. In the third generation, the process of splitting hybrids into morphotypes continues. There are hybrid plants with pyramidal and fusiform spike, awned and semi-awned, high and low. Compared with first-generation hybrids, the number of significant relationships in second-and third-generation hybrids is much higher. The explanation for this is that F2 and F3 hybrids have a wider range of genotypic and phenotypic variability. Splitting in F2 and subsequent generations is extremely diverse, since the parent varieties differed among themselves for a very large number of characters. The process of stabilization of F3 hybrids is not complete, in addition to the recombination of genes, the process of stabilizing the level of ploidy has not been completed. The obtained hybrid material is of interest as a theoretical one - for further genetic research, as well as practical - for selective use. Increasing the sensitivity of the hybrid to favorable and unfavorable conditions shows an increase in the phenotypic plasticity expressed by the bi regression coefficient. The reason of such as lies in the genetic determination of the norm of reaction, the phenotypic manifestation of which depends on the action of environment factors and their tension. The purpose of this study was to study the correlation relationships of hybrids F1, F2 and F3 obtained in different ways, plasticity and stability. Identify the likelihood of cytogenetic balanced forms in F3 and the ability to conduct selections in this generation.

Barley CMS detected in Finland in 1976 enabled growing of productive winter-barley F1 hybrids in the European winter-barley zone since 2002

My wide crossing program of barley (Hordeum vulgare s.l.) in 1976 yielded a system which could be used to produce F1 hybrid seeds. The genotypes were designated as msm1 (male sterile, maternal), and Rfm1a (restorer of fertility in msm1). I later found 19 other strains with dominant restorer alleles, which were carriers of a fertile cytoplasm. Hence, the restorer genes probably evolved in advance creating an opportunity for the cytoplasm to mutate to male sterility. Cytological studies revealed an uncontrolled secretion of sporopollenin in the sterile anthers, leading to their starvation and sterility. The Rfm1a gene was shown to cause an increase in the cytokinin activity of Fraction 7 in the root sap of barley, regardless of the cytoplasm type. In 1980, I found another male sterile cytoplasm, msm2, whose anther can also be restored by the Rfm1 alleles. The msm2 strain originally had complementary partial restorer genes and was found to be more responsive to such restorers than msm1. In Germany, the Rfm1 gene was recently translocated to a rye (Secale cereale) chromosome to study its response in CMS rye. The msm2 cytoplasm could be distinguished from msm1 with electron microscopy at the early stages of the anthers. The msm1 cytoplasm is not known to be associated with increased disease susceptibility, unlike the T-sterile cytoplasm formerly used to produce hybrid seeds of maize (Zea mays). Hybrid cvs: Seeds of msm1–Rfm1a were first requested from me by Hilleshög AB in Sweden. Hilleshög later became a part of Syngenta. Hilleshög techniques for sugar-beet hybrids were applied by Syngenta breeders to produce hybrid barley seeds. Syngenta introduced the first commercial winter-barley hybrid in the UK in 2002. Their hybrid cvs were marketed to countries growing winter-barley in Europe. The ha yields of their hybrids exceeded those of conventional cultivars or parental lines by about 1000 kg. In Spain, the winter-barley hybrid yielded 21 percent more than the conventional cultivars in 2015, when grown in the field scale. For the 2016 harvest, hybrids were sown in Germany on more than 140000 ha, which reflects 11.6 percent of the total feed barley area. In 2017, Syngenta launched a cashback scheme for, if their hybrid cultivars did not comfortably out-yield the farmer's conventional counterpart that season. Hybrid seeds must be acquired for each sowing. Unlike conventional monogenic barley cultivars, the hybrids exploit genetic variability and heterozygosity. Hybrid winter-barley is the most competitive of winter cereals with the aggressive weed Alopecurus myosuroides in the UK. Thick stems in new hybrids increase lodging resistance. The winter-barley hybrid ‘Wootan’ gave ha yields up to 6000 kg in Tammisaari, though incompletely winter-hardy in Finland. Maturing a month later than the hybrid ‘Hobbit’ and with optimal winterhardiness, winter-barley hybrids could exceed ha yields of 10000 kg in Finland. Some other breeding companies seem to work for hybrid barley, too.

Introgression of Powdery Mildew Resistance Gene Pm56 on Rye Chromosome Arm 6RS Into Wheat.

Powdery mildew, caused by the fungus Blumeria graminis f. sp. tritici, represents a yield constraint in many parts of the world. Here, the introduction of a resistance gene carried by the cereal rye cv. Qinling chromosome 6R was transferred into wheat in the form of spontaneous balanced translocation induced in plants doubly monosomic for chromosomes 6R and 6A. The translocation, along with other structural variants, was detected using in situ hybridization and genetic markers. The differential disease response of plants harboring various fragments of 6R indicated that a powdery mildew resistance gene(s) was present on both arms of rye chromosome 6R. Based on karyotyping, the short arm gene, designated Pm56, was mapped to the subtelomere region of the arm. The Robertsonian translocation 6AL⋅6RS can be exploited by wheat breeders as a novel resistance resource.

High‐throughput development of SSR marker candidates and their chromosomal assignment in rye (Secale cereale L.)

AbstractShotgun survey sequences of flow‐sorted individual rye chromosomes were data mined for the presence of simple sequence repeats (SSRs). For 787,850 putative SSR loci, a total of 358,660 PCR primer pairs could be designed and 51,138 nonredundant SSR marker candidates were evaluated by in silico PCR. Of the 51,138 SSR primer candidates, 1,277 were associated with 1,125 rye gene models. A total of 2,112 of the potential SSR markers were randomly selected to represent about equal numbers for each of the rye chromosomes, and 856 SSRs were assigned to individual rye chromosomes experimentally. Potential transferability of rye SSRs to wheat and barley was of low efficiency with 4.3% (2,189) and 0.4% (223) of rye SSRs predicted to be amplified in wheat and barley, respectively. This data set of rye chromosome‐specific SSR markers will be useful for the specific detection of rye chromatin introgressed into wheat as well as for low‐cost genetic and physical mapping in rye without the need for high‐tech equipment.

Two Rye Genes Responsible for Abnormal Development of Wheat⁻Rye Hybrids Are Linked in the Vicinity of an Evolutionary Translocation on Chromosome 6R.

The post-zygotic reproductive isolation (RI) in plants is frequently based on the negative interaction of the parental genes involved in plant development. Of special interest is the study of such types of interactions in crop plants, because of the importance of distant hybridization in plant breeding. This study is devoted to map rye genes that are incompatible with wheat, determining the development of the shoot apical meristem in wheat–rye hybrids. Linkage analysis of microsatellite loci, as well as genes of embryo lethality (Eml-R1) and hybrid dwarfness (Hdw-R1) was carried out in hybrids of Chinese Spring wheat with recombinant inbred lines as well as interline rye hybrids. Eml-R1 and Hdw-R1 could be mapped proximal and distal of two closely linked EST-SSR markers, Xgrm902 and Xgrm959, on rye chromosome 6R. Both rye genes are located on a segment of chromosome 6R that contains a breakpoint of evolutionary translocation between the ancestral chromosomes of homeologous groups 6 and 3. The obtained results are discussed in relation to genes interacting in developmental pathways as a class of causal genes of RI.

Variable Patterning of Chromatin Remodeling, Telomere Positioning, Synapsis, and Chiasma Formation of Individual Rye Chromosomes in Meiosis of Wheat-Rye Additions

Meiosis, the type of cell division that halves the chromosome number, shows a considerable degree of diversity among species. Unraveling molecular mechanisms of the meiotic machinery has been mainly based on meiotic mutants, where the effects of a change were assessed on chromosomes of the particular species. An alternative approach is to study the meiotic behavior of the chromosomes introgressed into different genetic backgrounds. As an allohexaploid, common wheat tolerates introgression of chromosomes from related species, such as rye. The behavior of individual pairs of rye homologues added to wheat has been monitored in meiotic prophase I and metaphase I. Chromosome 4R increased its length in early prophase I much more than other chromosomes studied, implying chromosome specific patterns of chromatin organization. Chromosome conformation affected clustering of telomeres but not their dispersion. Telomeres of the short arm of submetacentric chromosomes 4R, 5R, and 6R failed more often to be included in the telomere cluster either than the telomeres of the long arms or telomeres of metacentrics such as 2R, 3R, and 7R. The disturbed migration of the telomeres of 5RS and 6RS was associated with failure of synapsis and chiasma formation. However, despite the failed convergence of its telomere, the 4RS arm developed normal synapsis, perhaps because the strong increase of its length in early prophase I facilitated homologous encounters in intercalary regions. Surprisingly, chiasma frequencies in both arms of 4R were reduced. Similarly, the short arm of metacentric chromosome 2R often failed to form chiasmata despite normal synapsis. Chromosomes 1R, 3R, and 7R showed a regular meiotic behavior. These observations are discussed in the context of the behavior that these chromosomes show in rye itself.

Wheat chromosome instability in the selfed progeny of the double monosomics 1Rv-1A

Structural alterations of chromosomes are often found in wheat-rye hybrids. In the majority of cases modifications are observed for rye chromosomes, yet chromosome aberration cases are described for wheat, including the progeny of Triticum aestivum disomic and monosomic addition lines. Since wheat-rye substitution and translocation lines are the source of rye chromatin in wheat breeding programs, the information on possible chromosome changes in the genomes of introgressive forms is important. Chromosome behavior in F1 meiosis and chromosomal composition of F2 karyotypes for double monosomics 1Rv-1A were studied by applying C-banding, genomic in situ hybridisation (GISH) using rye genomic DNA, and sequential in situ hybridization using repetitive sequences pAs1, pSc119.2 and centromere specific pAet-06 as probes. The double monosomics 1Rv-1A were obtained by crossing of disomic substitution line with chromosome 1A replaced by Secale cereale 1Rv in the bread wheat Saratovskaya 29 (S29) background with S29. The results indicated a high frequency of bipolar chromosome 1Rv orientation, as compared to 1A, at metaphase I (MI) (58.6 and 34.7 % of meiocytes, respectively), and, at anaphase I (AI), chromatid segregation of 1Rv compared to 1A (70.53 and 32.14 % of meiocytes, respectively). In few cases desynapsis of wheat homologues was observed, at AI, the chromosomes randomly distributed between the poles or underwent chromatid segregation. At AI, the two wheat homologues separated onto sister chromatids in 10.89 % of cells.The plants F2 karyotypes were marked with aneuploidy not only of chromosomes 1A and 1Rv, but also of 1D, 2D, 3D, 3B, 3A, 4A, 6D, 6B, 6A, and 7D. Structural changes were observed for the chromosomes of the first homoeologous group (1Rv, 1A, 1D, 1B), as well as for 2B, 5D, 6B, and 7B. The chromosomes 1Rv and 6B often demonstrated aberrations. The types of aberrations were centromeric break, deletions of various sizes, and a changed repeat pSc119.2 localization pattern.

Populations of doubled haploids for genetic mapping in hexaploid winter triticale

To create a framework for genetic dissection of hexaploid triticale, six populations of doubled haploid (DH) lines were developed from pairwise hybrids of high-yielding winter triticale cultivars. The six populations comprise between 97 and 231 genotyped DH lines each, totaling 957 DH lines. A consensus genetic map spans 4593.9 cM is composed of 1576 unique DArT markers. The maps reveal several structural rearrangements in triticale genomes. In preliminary tests of the populations and maps, markers specific to wheat segments of the engineered rye chromosome 1R (RM1B) were identified. Example QTL mapping of days to heading in cv. Krakowiak revealed loci on chromosomes 2BL and 2R responsible for extended vernalization requirement, and candidate genes were identified. The material is available to all parties interested in triticale genetics.

Assessment of some genetic attributes in wheat (Triticum aestivum L.) using gene-specific molecular markers

Twenty-four wheat genotypes were characterized for the presence of three stress related genetic attributes using gene-specific molecular markers. Polymerase chain reaction (PCR) products of approximately 110 bp of 1RS rye chromosome fragment from 16 genotypes were obtained using specific primer pairs indicating the presence of translocation in these lines. The same genotypes were screened for the presence of dwarfing genes where 19 genotypes showed the presence of either the Rht-B1b or Rht-D1b allele having a semi-dwarf phenotype. Two of the genotypes (Kheri and Sufi) had wild type alleles in both the loci and two other genotypes showed the presence of double dwarf alleles (Rht-B1b + Rht-D1b). A 16.9 kDa HSP gene was characterized by validating a single-nucleotide polymorphism (SNP) linked with thermo tolerance in wheat. Thirteen of the 24 genotypes, which failed to amplify the specific PCR product due to the presence of an SNP, are expected to show tolerance for heat stress. Among the genotypes, Sonora-64, Balaka, Barkat, Aghrani and BARI Gom-24 (Prodip) tested positive for all the three markers evaluated (rye translocation, dwarfing genes and heat tolerance). These genotypes could be used to improve various stress tolerance attributes in wheat for future breeding programs.