1RS Chromosome Research Articles

A triplicated wheat-rye chromosome segment including several 12-OXOPHYTODIENOATE REDUCTASE III genes influences magnesium partitioning and impacts wheat performance at low magnesium supply

We previously reported a structural rearrangement between wheat (Triticum aestivum) and rye (Secale cereale) chromosomes 1BS/1RS that increased the dosage of 12-OXOPHYTODIENOATE REDUCTASE III (OPRIII) genes involved in jasmonate biosynthesis (henceforth, 1RW line), and that drastically reduced primary root growth relative to a control line with the intact 1RS chromosome (henceforth, 1RS). In this study, we show that the increased gene-dosage of this region is associated with increases in the shoot-root partitioning of magnesium (Mg). Moreover, both a CRISPR-edited 1RW line with reduced OPRIII dosage and the 1RW line treated with the jasmonate biosynthesis inhibitor ibuprofen showed reduced differences in shoot-root Mg partitioning than 1RW. The observed differences in Mg partitioning between 1RS and 1RW plants occur over a wide range of external Mg supplies and imply opposite trends of Mg accumulation in roots and shoots. Furthermore, we show an association between the increase of shoot-root Mg partitioning and increased tolerance of the 1RW line to low levels of Mg supply. In summary, our results provide evidence of the role of the jasmonate pathway on the dynamics of Mg accumulation in roots and shoots, which correlates with the performance of wheat plants under conditions of Mg scarcity.

Molecular Cytogenetic Characterization of Novel Wheat-Rye T1RS.1AL Translocation Lines with Resistance to Powdery Mildew and Stripe Rust Derived from the Chinese Rye Landrace Qinling.

Stripe rust and powdery mildew are serious diseases that severely decrease the yield of wheat. Planting wheat cultivars with powdery mildew and stripe rust resistance genes is the most effective way to control these two diseases. Introducing disease resistance genes from related species into the wheat genome via chromosome translocation is an important way to improve wheat disease resistance. In this study, nine novel T1RS.1AL translocation lines were developed from the cross of wheat cultivar Chuannong25 (CN25) and a Chinese rye Qinling. The results of non-denaturing fluorescence in situ hybridization and PCR showed that all new lines were homozygous for the T1RS.1AL translocation. These new T1RS.1AL translocation lines exhibited strong resistance to stripe rust and powdery mildew. The cytogenetics results indicated that the resistance of the new lines was conferred by the 1RS chromosome arms, which came from Qinling rye. The genetic analysis indicated that there were new dominant resistance genes on the 1RS chromosome arm resistant to stripe rust and powdery mildew, and their resistance patterns were different from those of Yr9, Pm8, and Pm17 genes. In addition, the T1RS.1AL translocation lines generally exhibited better agronomic traits in the field relative to CN25. These T1RS.1AL translocations have great potential in wheat-breeding programs in the future.

Pyramiding of transgenic immune receptors from primary and tertiary wheat gene pools improves powdery mildew resistance in the field.

Introgression of resistance genes from wild or related species is a common strategy to improve disease resistance of wheat cultivars. Pm17 is a gene that confers powdery mildew resistance in wheat. It encodes an NLR type of immune receptor and was introgressed from rye to wheat as part of the 1RS chromosome arm translocation several decades ago. So far it has not been possible to separate Pm17 from its co-introgressed rye genes due to suppressed recombination. Here we tested in the field transgenic Bobwhite wheat overexpressing Pm17 without any other rye genes. Four transgenic events showed high levels of PM17 protein accumulation, strong powdery mildew resistance, and no pleiotropic effects during three field seasons. We used a combined approach of transgene insertion and cross-breeding to generate lines co-expressing Pm17 and Pm3, or Pm17 and Pm8. Blumeria graminis f. sp. tritici infection tests confirmed additive, race-specific resistance of the two pyramided transgenes in lines Pm17+Pm3b and Pm17+Pm8. Furthermore, pyramided lines showed strong powdery mildew resistance during three field seasons. We conclude that the combination of overexpressed NLR genes from the extended gene pool broadens and diversifies wheat disease resistance.

Dynamics of Rye Translocations Frequency in Russian Common Wheat <i>Triticum aestivum</i> L. Cultivars

The widespread using 1RS/1BL and 1RS/1AL translocation cultivars in wheat breeding was due to their high complex resistance provided by genes on 1RS chromosomes. Numerous data on the emergence of new virulent pathogen races that caused the loss of protective properties by genes on 1RS make it relevant to analyse the prospects for using both rye translocations in modern breeding programs. The use of various genetic sources of the 1RS rye chromosome in introgressive hybridization poses the problem of studying the diversity of 1RS linkage groups. We have studied the rye translocations dynamics in 240 genotypes of the wheat cultivars from 3 breeding centers of the Russian Federation. Multiple alleles of storage protein genes specific for 1RS were used to mark 1RS. The effectiveness of 1RS resistance genes to a number of pathogens, in particular to powdery mildew and stem rust, has been established. The grain quality dynamics of the 1RS/1BL cultivars has been traced. A statistically significant grain quality improvement of winter wheat cultivars since the 2000s has been confirmed. The spring cultivars quality does not depend on the presence of rye translocations in the genotypes. Accumulation of cultivars with TR:1RS/1BL observed in all three centers. A high allelic diversity of the secalin coding locus on 1RS chromosome was shown. However, all cultivars with rye translocations, regardless of 1RS origin, carried the same allele. Possible reasons for this uniformity are discussed. Translocation 1RS/1AL was not detected in the studied cultivars. Possible reasons are discussed.

Cytological and genetic effects of rye chromosomes 1RS and 3R on the wheat-breeding founder parent Chuanmai 42 from southwestern China.

The online version contains supplementary material available at 10.1007/s11032-023-01386-0.

Development and characterization of a novel common wheat–Mexico Rye T1DL·1RS translocation line with stripe rust and powdery mildew resistance

Rye (Secale cereale L., 2n=2x=14, RR) is a significant genetic resource for improving common wheat because of its resistance to multiple diseases and abiotic-stress tolerant traits. The 1RS chromosome from the German cultivated rye variety Petkus is critical in wheat breeding. However, its weakened disease resistance highlights the need to identify new resources. In the present study, a novel derived line called D27 was developed from common wheat and Mexico Rye. Cytological observations characterized the karyotype of D27 as 2n=42=21 II. Genomic in situ hybridization indicated that a pair of whole-arm translocated Mexico Rye chromosomes were inherited typically in the mitotic and meiosis stages of D27. Experiments using fluorescence in situ hybridization (FISH) and gliadin electrophoresis showed that D27 lacked wheat 1DS chromosomes. They were replaced by 1RS chromosomes of Mexico Rye, supported by wheat simple-sequence repeat markers, rye sequence characterized amplified region markers, and wheat 40K SNP array analysis. The wheat 1DS chromosomes could not be detected by molecular markers and wheat SNP array, but the presence of rye 1RS chromosomes was confirmed. Agronomic trait assessments indicated that D27 had a higher tiller number and enhanced stripe rust and powdery mildew resistance. In addition, dough properties analysis showed that replacing 1DS led to higher viscosity and lower dough elasticity in D27, which was beneficial for cake making. In conclusion, the novel cytogenetically stable common wheat–Mexico Rye T1DL·1RS translocation line D27 offers excellent potential as outstanding germplasm in wheat breeding programs focusing on disease resistance and yield improvement. Additionally, it can be valuable for researching the rye 1RS chromosome’s genetic diversity.

Variations of subtelomeric tandem repeats and rDNA on chromosome 1RS arms in the genus Secale and 1BL.1RS translocations

BackgroundThe wheat-rye 1BL.1RS translocations have played an important role in common wheat breeding programs. Subtelomeric tandem repeats have been often used to investigate polymorphisms of 1RS arms, but further research about their organizations on the 1RS chromosome is needed.Results162 1RS arms from a wild rye species (Secale strictum) and six cultivated rye accessions (Secale cereale L.) (81 plants), 102 1BL.1RS and one 1AL.1RS translocations were investigated using oligo probes Oligo-TaiI, Oligo-pSc119.2–1, Oligo-pTa71A-2, Oligo-pSc200 and Oligo-pSc250, which were derived from tandem repeats TaiI, pSc119.2, pTa71, pSc200 and pSc250, respectively. The variations of 1RS arms were revealed by signal intensity of probes Oligo-pSc119.2–1, Oligo-pTa71A-2, Oligo-pSc200 and Oligo-pSc250. Proliferation of rDNA sequences on the 1RS chromosomes was observed. According to the presence of probe signals, 34, 127 and 144 of the 162 1RS arms contained TaiI, pSc200 and pSc250, respectively, and all of them contained pSc119.2 and pTa71. Most of the 1RS arms in rye contained three kinds of subtelomeric tandem repeats, the combination of pSc119.2, pSc200 and pSc250 was most common, and only eight of them contained TaiI, pSc119.2, pSc200 and pSc250. All of the 1RS arms in 1BL.1RS and 1AL.1RS translocations contained pSc119.2, pTa71, pSc200 and pSc250, but the presence of the TaiI family was not observed.ConclusionNew organizations of subtelomeric tandem repeats on 1RS were found, and they reflected new genetic variations of 1RS arms. These 1RS arms might contain abundant allelic diversity for agricultural traits. The narrow genetic base of 1RS arms in 1BL.1RS and 1AL.1RS translocations currently used in agriculture is seriously restricting their use in wheat breeding programs. This research has found new 1RS sources for the future restructuring of 1BL.1RS translocations. The allelic variations of these 1RS arms should be studied more intensely as they may enrich the genetic diversity of 1BL.1RS translocations.

Characterization of PmBN418, a wheat powdery mildew resistance gene on the rye 1RS chromosome arm

AbstractPowdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a disease of global importance, and new powdery mildew resistance genes that can be directly used in cultivar development are urgently needed. A recombinant inbred line population from ‘CI 17884’ × ‘Bainong 418’ was genotyped using single nucleotide polymorphism markers generated from genotyping‐by‐sequencing, and evaluated for responses to Great Plains Bgt isolates OKS(14)‐B‐3‐1 and NEI‐1‐3. Genetic mapping identified a powdery mildew resistance gene, designated PmBN418, on a 1BL.1RS translocation segment in Bainong 418. Given that PmBN418 conferred resistance to Bgt isolates virulent to Pm8 that resides on the chromosome arm 1RS translocated from rye (Secale cereale L.) cv. ‘Petkus’, PmBN418 is either a new gene or a new allele of Pm8. Phenotypic and genomic data analyses indicated segregation distortion of the powdery mildew resistance gene due to reduced transmission of the wheat (Triticum aestivum L.)–rye 1BL.1RS translocation segment from Bainong 418, while the wheat–Triticum speltoides translocation segment 7S#1 in CI 17884 was preferentially transmitted. Bainong 418, a high‐yielding cultivar with good resistance to several U.S. Bgt isolates, is a useful resistance source for wheat breeding, and the availability of the Kompetitive Allele Specific PCR (KASP) marker KASP‐1RS‐1 makes marker‐assisted introgression of PmBN418 into locally adapted cultivars feasible.

Characterization of an Incomplete Leaf Rust Resistance Gene on Chromosome 1RS and Development of KASP Markers for Lr47 in Wheat.

Leaf rust, caused by Puccinia triticina, is one of the most common wheat (Triticum aestivum) diseases in the Great Plains of the United States. A population of recombinant inbred lines from CI 17884 × 'Bainong 418' was evaluated for responses to leaf rust race Pt52-2 and genotyped using single nucleotide polymorphism (SNP) markers. Quantitative trait locus analysis identified a minor gene for resistance to leaf rust, designated QLr.stars-1RS, on the 1BL.1RS translocation segment in 'Bainong 418', and another leaf rust resistance gene, Lr47, on chromosome 7A of CI 17884. Lr47, originally identified in CI 17884 and located in a wheat-T. speltoides translocation segment 7S#1S, remains one of only a few race-specific resistance genes still effective in the Great Plains. A set of 7A-specific simple sequence repeat markers were developed and used to genotype CI 17884 and a pair of near-isogenic lines differing in the presence or absence of 7S#1S, PI 603918, and 'Pavon F76'. Haplotype analysis indicated that the estimated length of 7S#1S was 157.23 to 174.42 Megabases, accounting for ∼23% of the 7A chromosome. Two SNPs on 7S#1S and four SNPs on the 1RS chromosome arm were converted to Kompetitive allele-specific PCR (KASP) markers, which were subsequently validated in a panel of cultivars and elite breeding lines released within the last decade. Of these, one- and two-KASP markers are specific to the 1RS chromosome arm and 7S#1S, respectively, indicating that they can facilitate the introgression of Lr47 and QLr.stars-1RS into locally adapted wheat cultivars and breeding lines.

Effects of the 1BL/1RS translocation on 24 traits in a recombinant inbred line population

The 1BL/1RS translocation is widespread in a large number of wheat varieties. In this study, we comprehensively evaluated the effects of the 1BL/1RS translocation on 24 traits in a recombinant inbred line population derived from the cross between 20828 and Chuannong16. The phenotypic data was from multiple environments and major loci for a given trait were excluded to avoid their interference with the effects of 1BL/1RS translocation. Comparison results showed that 1RS chromosome arm carried lines had positive effect on increasing maximum root length and spike density. While 1BS chromosome arm carried lines had positive effects on increasing plant height, grain number per spike, effective tiller, root tip number, and resistance to stripe rust. The stripe rust resistance genes, Yr15 detected on 1BS in this study and QYr.sicau-1B.1 identified previously on 1BL were both derived from 20828. These results revealed the genetic mechanism of near-immune resistance to stripe rust in 20828 that has been utilized as a breeding parent for over a decade, and thus possibly accelerate its breeding utilization. This study combined with previous studies indicated that 1BS chromosome arm is likely beneficial to yield increase, while 1RS is more helpful for drought tolerance improvement.

Genetic diversity in common wheat lines revealed by fluorescence in situ hybridization

Molecular markers and phenotyping have been widely used to evaluate wheat germplasm diversity. However, the feasibility of using chromosome fluorescence in situ hybridization (FISH) to evaluate wheat genetic diversity has not been well investigated. In this study, seventy-six representative Chinese wheat lines in main wheat production area were selected and investigated with multicolour FISH using Oligo-pTa535, Oligo-pSc119.2 and Oligo-(GAA)8 probes. The results indicated that wheat chromosomes can be clearly recognized by FISH. For wheat A, B and D genomes, the number of FISH types ranged from 2 to 7, 2 to 6 and 1 to 5, respectively. The average number of FISH types in the A and B genomes was higher than that in the genome D. The rye-derived 1RS chromosome in wheat background could also be clearly detected by these probes. The frequency of 1RS in Chinese wheat lines investigated was 48.7%, and most (94.6%) of them belonged to 1BL.1RS. The genetic relationships among the seventy-six Chinese wheat lines subjected to FISH were divided into three clusters, e.g., CL1, CL2 and CL3. Those wheat lines derived from Shandong and Henan Provinces were mainly located in clusters CL1 and CL3, respectively, which may suggest that the FISH type is associated with the adaptation of wheat. These results also indicated that multicolour FISH using a combination of three different oligo-probes generates sufficiently diverse hybridization patterns among wheat lines to evaluate the genetic diversity of wheat.

Evolutionary divergence of the rye Pm17 and Pm8 resistance genes reveals ancient diversity.

We have isolated a novel powdery mildew resistance gene in wheat that was originally introgressed from rye. Further analysis revealed evolutionary divergent history of wheat and rye orthologous resistance genes. Wheat production is under constant threat from a number of fungal pathogens, among them is wheat powdery mildew (Blumeria graminis f. sp. tritici). Deployment of resistance genes is the most economical and sustainable method for mildew control. However, domestication and selective breeding have narrowed genetic diversity of modern wheat germplasm, and breeders have relied on wheat relatives for enriching its gene pool through introgression. Translocations where the 1RS chromosome arm was introgressed from rye to wheat have improved yield and resistance against various pathogens. Here, we isolated the Pm17 mildew resistance gene located on the 1RS introgression in wheat cultivar 'Amigo' and found that it is an allele or a close paralog of the Pm8 gene isolated earlier from 'Petkus' rye. Functional validation using transient and stable transformation confirmed the identity of Pm17. Analysis of Pm17 and Pm8 coding regions revealed an overall identity of 82.9% at the protein level, with the LRR domains being most divergent. Our analysis also showed that the two rye genes are much more diverse compared to the variants encoded by the Pm3 gene in wheat, which is orthologous to Pm17/Pm8 as concluded from highly conserved upstream sequences in all these genes. Thus, the evolutionary history of these orthologous loci differs in the cereal species rye and wheat and demonstrates that orthologous resistance genes can take different routes towards functionally active genes. These findings suggest that the isolation of Pm3/Pm8/Pm17 orthologs from other grass species, additional alleles from the rye germplasm as well as possibly synthetic variants will result in novel resistance genes useful in wheat breeding.

Chromosomes 1BS and 1RS for control of male fertility in wheats and triticales with cytoplasms of Aegilops kotschyi, Ae. mutica and Ae. uniaristata.

Engineered chromosomes 1BS and 1RS offer a new alternative in the development of hybrid systems in bread wheat and triticale. In the cytoplasmic male sterility system for hybrid wheat based on the cytoplasm of Triticum timopheevi fertility restoration is difficult, with few good restorer genes available. In the system based on the cytoplasms of Aegilops kotschyi, Ae. uniaristata and Ae. mutica, essentially all chromosomes 1B carry locus Rf multi that restores male fertility; male sterility manifests itself in wheats with the 1RS.1BL translocation where 1BS chromosome arm is missing. To generate male sterile wheats without the 1RS.1BL translocation, the 1BS arm was cytogenetically engineered to replace the segment with Rf multi with two short inserts of rye chromatin. Conversely, to enhance fertility restoration by doubling the number of restorers present for eventual use in wheat and triticale, a region of 1BS with Rf multi was inserted into 1RS. Alloplasmic wheats with Rf multi removed were completely male sterile; alloplasmic wheats with engineered 1RS carrying Rf multi and without normal 1B were male fertile. An exception to the ubiquitous presence of Rf multi is T. spelta var. duhamelianum; four accessions tested in this study gave inconsistent results but some did not restore male fertility. Engineered chromosomes 1BS and 1RS and chromosomes 1B of T. spelta offer a new alternative for practical application of a cytoplasmic male sterility system in the development of hybrid wheat and hexaploid triticale.

De novo balanced complex chromosome rearrangements involving chromosomes 1B and 3B of wheat and 1R of rye.

Complex chromosome rearrangements (CCRs) are defined as structural abnormalities involving more than two chromosome breaks, coupled with exchanges of chromosomal segments. Information on CCRs in plants is limited. In the present study, a plant (26-4) harboring translocation chromosomes 1RS.1BL and 4RS.4DL was selected from a double monosomic (1R and 4R) addition line, which was derived from the hybrid between wheat cultivar MY11 and a Chinese local rye variety. The genome of the plant with double alien translocation chromosomes in the monosomic form showed more instability than that harboring a single translocation. The CCRs involving chromosomes 1RS.1BL and 3B, which were generated de novo in this plant, showed double monosomic translocation chromosomes. A new CCR line with balanced reciprocal translocations 1RS.3BL and 3BS.1BL was developed, which presented normal morphological traits of wheat and underwent rapid growth in the field. A new 1RS.1BL translocation line was also selected from the progeny of plant 26-4. The CCRs and simple 1RS.1BL translocation lines showed significant improvement in grain yield, number of spikes per square meter, kernel number per spike, and resistance to stripe rust and powdery mildew. The CCR line exhibited better agronomic traits and adult plant resistance in the field than its sister line, which harbored a simple 1RS.1BL translocation. The CCRs are remarkable genetic resources for crop improvement.

Distribution of Wheat-Rye Translocation Line T1BL·1RS in Wheat and Its Association with Fusarium Head Blight Resistance

The short arm of 1R chromosome (1RS) of rye carries resistant genes to stripe rust, leaf rust, stem rust, powdery mil- dew and aphids. To understand if 1RS also mediates resistance to wheat Fusarium head blight (FHB), we genotyped a panel of 192 wheat accessions from diverse geographic regions and a population of recombinant inbred lines (RIL) consisting of 184 lines developed from the cross of Ning 7840 and Chokwang by 1RS-specific molecular marker Xscm9 and evaluated FHB severities in three consecutive seasons in greenhouses using single floret inoculation method. The results demonstrated that 22 of 192 acces- sions carried a T1BL1RS translocation, and the mean FHB severity (PSS) of varieties carrying T1BL1RS translocation was sig- nificantly lower than that of lines without the translocation across the three experiments (P < 0.05), indicating 1RS may have a positive effect on reducing FHB severity. 1RS-specific marker Xscm9 and Genome in situ hybridization (GISH) showed Ning 7840 carries T1BL1RS translocation. In the population of RILs, irrespective of Fhb1 locus, the mean PSS of lines with T1BL1RS translocation was significantly lower than that of those lines without T1BL1RS. The effects of Fhb1 and 1RS on FHB resistance were additive and the interactions between them were not significant (P = 0.48). The results of this study suggested that 1RS of rye most likely carries the genes resistant to FHB.

Cytogenetic and Embryologic Analyses of the Mechanism of Parthenogenesis Induced by 1BL/1RS Male Sterile Lines in Wheat

In this study, we employed electron microscopy to investigate the cytogenetic and embryologic mechanisms of parthenogenesis induced in the 1BL/1RS male sterile lines of wheat. Analysis of the root tips and acid polyacrylamide gel electrophoresis indicated that all of the male sterile lines and their maintainer lines were 1BL/1RS translocation lines, whereas the restorer lines were non-1BL/1RS translocation lines. Furthermore, the chromosomes of 1BL/1RS wheat lines with T. aestivum cytoplasm and Aegilops cytoplasm (include Ae. kotschyi, Ae. ventricosa, Ae. variabilis) paired abnormally at different rates during meiotic metaphase I (MMI). The translocated segment size of the 1RS chromosome and the specific nuclear–alloplasm interaction impaired the pairing of homologous chromosome in the background of the specific Aegilops cytoplasm at MMI. In addition, the frequency of abnormal chromosomal pairing was directly affected by the frequency of haploid production induced by parthenogenesis. The results of this s...

The wheat Sr50 gene reveals rich diversity at a cereal disease resistance locus.

We identify the wheat stem rust resistance gene Sr50 (using physical mapping, mutation and complementation) as homologous to barley Mla, encoding a coiled-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) protein. We show that Sr50 confers a unique resistance specificity different from Sr31 and other genes on rye chromosome 1RS, and is effective against the broadly virulent Ug99 race lineage. Extensive haplotype diversity at the rye Sr50 locus holds promise for mining effective resistance genes.

1RS translocation in Croatian winter wheat varieties

The translocation between the short arm of chromosome 1R of rye and the long arm of chromosome 1A, 1B or 1D of wheat represents practically the most common introduced foreign genes into the genome of hexaploid wheat. 1RS chromosome arm represents a source of different useful genes, associated with increased disease resistance, improved adaptability, stress tolerance, and increased stability and level of yield. On the other hand, translocation is associated with poor technological quality of wheat as a result of the presence of secalin and reduced number of gluten loci. The aim of this study was to determine the prevalence of 1RS translocation among some Croatian winter wheat varieties using molecular markers. The study included 40 varieties of which 23 Croatian. Four pairs of primers: RIS, SCM9, RYE-NOR and PAW161 were used for determination of translocation. The presence of translocation was determined in 12 of 40 (30%) varieties, while among the Croatian wheat varieties translocation had 8 of 23 (34.78%) varieties (Zlatna Dolina, Barbara, Nova Žitarka, Marija, Prima, Kuna, Koleda and Dea).

Androgenetic ability in euplasmic lines of common wheat and alloplasmic recombinant lines (H. vulgare)–T. aestivum carrying 1RS.1BL and 7DL-7Ai translocations and development of double haploid lines

Androgenic ability was studied in anther cultures of euplasmic lines of common wheat and alloplasmic recombinant lines (H. vulgare)–T. aestivum with 1RS.1BL and 7DL-7Ai translocations. The ability to produce androgenic structures and plantlet regeneration are suppressed in lines carrying both translocations. Alloplasmic recombinant lines (H. vulgare)–T. aestivum with the 1RS.1BL and 7DL-7Ai translocations, as well as alloplasmic lines with the 1RS.1BL translocation, are characterized by their increased ability to form androgenic structures, including polyembryos, and plantlet regeneration compared to euplasmic lines. The inducing reciprocal influence of barley cytoplasm and rye chromosome 1RS on the androgenesis ability of lines (H. vulgare)–T. aestivum with 1RS.1BL and 7DL-7Ai translocations is discussed. Double haploid lines were developed from androgenic plants with spontaneously doubled chromosome numbers and restored fertility. Of the lines carrying the translocations, the most promising with regard to the exhibition of agronomic valuable traits and resistance to diseases were selected in order to utilize them in breeding programs.

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.