Genome architecture of the allotetraploid wild grass Aegilops ventricosa reveals its evolutionary history and contributions to wheat improvement.

The allotetraploid wild grass Aegilops ventricosa (2n=4X=28, genome DvDvNvNv) has been recognized as an important germplasm resource for wheat improvement due to its ability to tolerate biotic stresses. Especially 2NvS segment from Aegilops ventricosa, as a stable and effective resistance source, has greatly contributed to wheat improvement. The 2NvS/2AS translocation is a prevalent chromosomal translocation between common wheat and wild relatives, ranking just behind the 1B/1R translocation in importance for modern wheat breeding. Here, we assembled a high-quality chromosome-level reference genome of Ae. ventricosa RM271 with a total length of 8.67 Gb. Phylogenomic analyses revealed that the progenitor of the Dv subgenome of Ae. ventricosa was Ae. tauschii ssp. tauschii (genome DD); in contrast, the progenitor of the D subgenome of bread wheat (Triticum aestivum L.) was Ae. tauschii ssp. strangulata (genome DD). The oldest polyploidization time of Ae. ventricosa occurred ∼0.7 million years ago. The Dv subgenome of Ae. ventricosa was less conserved than the D subgenome of bread wheat. Construction of a graph-based pangenome of 2AS/6NvL (originally known as 2NvS) segments from Ae. ventricosa and other genomes in the Triticeae enables us identifying candidate resistance genes sourced from Ae. ventricosa. We identified 12 nonredundant introgressed segments from the Dv and Nv subgenomes using a large winter wheat collection representing the full diversity of the wheat European genetic pool, and 29.40% of European wheat varieties inherited at least one of these segments. The high-quality RM271 reference genome will provide a basis for cloning key genes, including the Yr17-Lr37-Sr38-Cre5 resistance gene cluster in Ae. ventricosa, and facilitate the full use of elite wild genetic resources to accelerate wheat improvement.

Rice Promoter Editing: An Efficient Genetic Improvement Strategy.

Gene expression levels in rice (Oryza sativa L.) and other plant species are determined by the promoters, which directly control phenotypic characteristics. As essential components of genes, promoters regulate the intensity, location, and timing of gene expression. They contain numerous regulatory elements and serve as binding sites for proteins that modulate transcription, including transcription factors and RNA polymerases. Genome editing can alter promoter sequences, thereby precisely modifying the expression patterns of specific genes, and ultimately affecting the morphology, quality, and resistance of rice. This paper summarizes research on rice promoter editing conducted in recent years, focusing on improvements in yield, heading date, quality, and disease resistance. It is expected to inform the application of promoter editing and encourage further research and development in crop genetic improvement with promote.

Investigation of chromosomal genetic characteristics and identification of structural variation in the offspring of hexaploid triticale×hexaploid wheat.

Hexaploid triticale is an important genetic resource for genetic improvement of common wheat, which can broaden the genetic basis of wheat. In order to lay a foundation for the subsequent research and utilization of triticale germplasm materials, the chromosomal genetic characteristics of cross and backcross offspring of hexaploid triticale×hexaploid wheat were investigated in the process of transferring rye chromatin from hexaploid triticale to hexaploid wheat. Hybrid and backcross combinations were prepared with hexaploid triticale 16yin171 as the maternal parent and hexaploid wheat Chuanmai62 as the paternal parent. The chromosomes in root tip cells of F1, BC1F1 and BC1F2 plants were traced and identified non-denaturing florescence in situ hybridization (ND-FISH). The results indicated that the backcross setting rate of hybrid F1 was 2.61%. The transmission frequency of 2R chromosome was the highest in BC1F1 plants while the transmissibility of rye chromosome in BC1F2 plant was 6R>4R>2R, and the 5B-7B wheat translocation in BC1F2 plants showed severe segregation. A total of 24 structural variant chromosomes were observed both in BC1F1 and BC1F2 plants, including chromosome fragments, isochromosomes, translocations, and dicentric chromosomes. In addition, the seed length and 1000-grain weight of some BC1F2 plants were better than that of the hexaploid wheat parent Chuanmai 62. Therefore, multiple backcrosses should be adopted as far as possible to make the rapid recovery of group D chromosomes, ensuring the recovery of fertility in offspring, when hexaploid tritriale is used as a bridge to introduce rye genetic material into common wheat. At the same time, the potential application value of chromosomal structural variation materials should be also concerned.

Preliminary exploration of hepatic parenchymal near-infrared fluorescence imaging technique via retrograde biliary approach: a feasibility study (with video).

This paper explores the feasibility and principle of hepatic parenteral fluorescence imaging technology after retrograde injection of indocyanine green (ICG) through endoscopic nasobiliary drainage (ENBD). The data were collected from 53 patients with cholecystolithiasis and choledocholithiasis, from October 2022 to March 2023, diagnosed by fluorescence imaging technique retrograde biliary approach (FIT-RB). We divided the patients into two groups according to the features of liver parenchyma, the poor group (n = 34, including scattered or no imaging) and the good group (n = 19, regular uniform imaging). We compared and analyzed the perioperative results of the two groups and explored the influencing factors of the success of FIT-RB and the ICG concentration suitable for this imaging technique. The good imaging rate of the 53 enrolled cases was 35.8%. The bilirubin level before ENBD and laparoscopic cholecystectomy in the poor group was significantly higher than that in the good group (P < 0.001). The proportion of higher ICG concentrations (0.5 mg/mL) was significantly higher in the good group (P = 0.028). Our results demonstrated that the success rate of good imaging was 4.53 times higher than that of low-dose ICG (0.125 or 0.25 mg/L) cases at 0.5 mg/ml of ICG. The level of total bilirubin and direct bilirubin were negatively correlated with the imaging effect, and total bilirubin and direct bilirubin levels were important predictors of the efficacy of FIT-RB. FIT-RB is safe and feasible in patients with low site bilirubin levels. An ICG concentration of 0.5 mg/ml may be ideal for implementing this technique.

Comparison of short-term outcomes between robotic and laparoscopic liver resection: a meta-analysis of propensity score-matched studies.

OBJECTIVE: This meta-analysis aimed to compare short-term outcomes between robotic liver resection (RLR) and laparoscopic liver resection (LLR) using data collected from propensity score-matched studies. METHODS: The PubMed, Cochrane Library, and Embase databases were searched to collect propensity score-matched studies comparing RLR and LLR. Relevant data were extracted and analyzed. Odds ratios (ORs) and standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated using fixed-effect or random-effect models. Meta-regression analysis was performed for primary outcome measures. Subgroup analyses and sensitivity analyses were performed for outcomes exhibiting high heterogeneity. Quality of evidence was evaluated using the Grading of Recommendations, Assessment, Development and Evaluation framework. RESULTS: Twenty-two propensity score-matched studies were included to comprise 5272 patients (RLR group, 2422 cases; LLR group, 2850 cases). Intraoperative blood loss (SMD=-0.31 ml, 95% CI -0.48 to -0.14; P =0.0005), open conversion (OR=0.46, 95% CI 0.37-0.58; P <0.0001), and severe complications (OR=0.76, 95% CI 0.61-0.95; P =0.02) were significantly lower in the RLR group. Operation time, odds of use, and duration of Pringle maneuver, length of hospital stay, and odds of intraoperative blood transfusion, overall complications, R0 resection, reoperation, 30-day readmission, 30-day mortality, and 90-day mortality did not significantly differ between the groups. Further subgroup and sensitivity analyses suggested that the results were stable. Meta-regression analysis did not suggest a correlation between primary outcomes and study characteristics. The quality of evidence for the primary outcomes was medium or low, while that for the secondary outcomes was medium, low, or very low. CONCLUSION: Although some short-term outcomes are similar between RLR and LLR, RLR is superior in terms of less blood loss and lower odds of open conversion and severe complications. In the future, RLR may become a safe and effective replacement for LLR.

Laparoscopic cholecystectomy assisted by combined intravenous and intracholecystic fluorescent cholangiography: a case report.

This case report describes a laparoscopic approach using fluorescence imaging guidance to treat gangrenous cholecystitis with perforation (GCP). A male patient in his early 60s presented with 3 days of right upper abdominal pain. Computed tomography and ultrasonography findings were consistent with a stone incarcerated in the gallbladder neck, GCP, and localized peritonitis. Percutaneous gallbladder drainage was initially performed, followed by laparoscopic cholecystectomy 7 days later, using combined intravenous and intracholecystic fluorescent cholangiography. This technique allowed visualization of the cystic and common bile ducts during surgery and enabled safe removal of the diseased gallbladder. The patient recovered well without complications, and reported no pain or discomfort at a 2-month follow-up.

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

Rye (Secale cereale L.) is an important genetic resource for improving the disease resistance of wheat. An increasing number of rye chromosome segments have been transferred into modern wheat cultivars via chromatin insertions. In this study, 185 recombinant inbred lines (RILs) derived from a cross between a wheat accession containing rye chromosomes 1RS and 3R and a wheat-breeding founder parent Chuanmai 42 from southwestern China were used to decipher the cytological and genetic effects of 1RS and 3R via fluorescence/genomic in situ hybridization and quantitative trait locus (QTL) analyses. Chromosome centromere breakage and fusion were detected in the RIL population. Additionally, the recombination of chromosomes 1BS and 3D from Chuanmai 42 was completely suppressed by 1RS and 3R in the RIL population. In contrast to chromosome 3D of Chuanmai 42, rye chromosome 3R was significantly associated with white seed coats and decreased yield-related traits, as revealed by QTL and single marker analyses, whereas it had no effect on stripe rust resistance. Rye chromosome 1RS did not affect yield-related traits and it increased the susceptibility of plants to stripe rust. Most of the detected QTLs that positively affected yield-related traits were from Chuanmai 42. The findings of this study suggest that the negative effects of rye-wheat substitutions or translocations, including the suppression of the pyramiding of favorable QTLs on paired wheat chromosomes from different parents and the transfer of disadvantageous alleles to filial generations, should be considered when selecting alien germplasm to enhance wheat-breeding founder parents or to breed new varieties. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01386-0.

OsTST1, a key tonoplast sugar transporter from source to sink, plays essential roles in affecting yields and height of rice (Oryza sativa L.).

MAIN CONCLUSION: OsTST1 affects yield and development and mediates sugar transportation of plants from source to sink in rice, which influences the accumulation of intermediate metabolites from tricarboxylic acid cycle indirectly. Tonoplast sugar transporters (TSTs) are essential for vacuolar sugar accumulation in plants. Carbohydrate transport across tonoplasts maintains the metabolic balance in plant cells, and carbohydrate distribution is crucial to plant growth and productivity. Large plant vacuoles store high concentrations of sugars to meet plant requirements for energy and other biological processes. The abundance of sugar transporter affects crop biomass and reproductive growth. However, it remains unclear whether the rice (Oryza sativa L.) sugar transport protein OsTST1 affects yield and development. In this study, we found that OsTST1 knockout mutants generated via CRISPR/Cas9 exhibited slower development, smaller seeds, and lower yield than wild type (WT) rice plants. Notably, plants overexpressing OsTST1 showed the opposite effects. Changes in rice leaves at 14 days after germination (DAG) and at 10 days after flowering (DAF) suggested that OsTST1 affected the accumulation of intermediate metabolites from the glycolytic pathway and the tricarboxylic acid (TCA) cycle. The modification of the sugar transport between cytosol and vacuole mediated by OsTST1 induces deregulation of several genes including transcription factors (TFs). In summary, no matter the location of sucrose and sink is, these preliminary results revealed that OsTST1 was important for sugar transport from source to sink tissues, thus affecting plant growth and development.

Laparoscopic or open liver resection for intrahepatic cholangiocarcinoma: A meta-analysis and systematic review.

Background: Although laparoscopic hepatectomy has been widely used in the treatment of benign and malignant liver diseases, its applicability in intrahepatic cholangiocarcinoma (ICC) is controversial. We conducted a meta-analysis to compare the short-term and long-term outcomes of laparoscopic hepatectomy (Lap-ICC) and open hepatectomy (Open-ICC) in ICC patients. Methods: The PubMed, Web of science, Cochrane Library, China National Knowledge Infrastructure and other databases were searched for the relevant literature. The research data were extracted according to the inclusion and exclusion criteria. Results: Seventeen studies, including 3975 ICC patients, were selected for the meta-analysis. Compared to Open-ICC, Lap-ICC had lower rates of lymph node dissection (OR=0.44, P=0.01) and metastasis (OR=0.58, P=0.03), along with less intraoperative bleeding (MD=-128.43 ml, P<0.01) lower blood transfusion rate (OR=0.43, P<0.01), shorter hospital stay (MD=-2.75 day, P<0.01), higher R0 resection rate (OR=1.60, P<0.01), and lower tumor recurrence rate (OR=0.67, P=0.01). However, there was no difference between the two groups in terms of operation time, number of lymph node dissection, incision margin distance, overall complications rate, severe complications rate, and the 1-, 3- and 5-year DFS and OS rates. Conclusion: Laparoscopic hepatectomy is partially superior to open hepatectomy in terms of less bleeding, shorter hospital stay and higher R0 resection rate, while the long-term efficacy of the two approaches is similar.

Location of Tandem Repeats on Wheat Chromosome 5B and the Breakpoint on the 5BS Arm in Wheat Translocation T7BS.7BL-5BS Using Single-Copy FISH Analysis.

Wheat (Triticum aestivum L.) is rich in tandem repeats, and this is helpful in studying its karyotypic evolution. Some tandem repeats have not been assembled into the wheat genome sequence. Alignment using the blastn tool in the B2DSC web server indicated that the genomic sequence of 5B chromosome (IWGSC RefSeq v2.1) does not contain the tandem repeat pTa-275, and the tandem repeat (GA)26 distributed throughout the whole 5B chromosome. The nondenaturing fluorescence in situ hybridization (ND-FISH) using the oligonucleotide (oligo) probes derived from pTa-275 and (GA)26 indicated that one signal band of pTa-275 and two signal bands of (GA)26 appeared on the 5B chromosome of Chinese Spring wheat, indicating the aggregative distribution patterns of the two kinds of tandem repeats. Single-copy FISH indicated that the clustering region of pTa-275 and the two clustering regions of (GA)26 were located in ~160-201 Mb, ~153-157 Mb, and ~201-234 Mb intervals, respectively. Using ND-FISH and single-copy FISH technologies, the translocation breakpoint on the 5BS portion of the translocation T7BS.7BL-5BS, which exists widely in north-western European wheat cultivars, was located in the region from 157,749,421 bp to 158,555,080 bp (~0.8 Mb), and this region mainly contains retrotransposons, and no gene was found. The clustering regions of two kinds of tandem repeats on wheat chromosome 5B were determined and this will be helpful to improve the future sequence assembly of this chromosome. The sequence characteristics of the translocation breakpoint on the translocation T7BS.7BL-5BS obtained in this study are helpful to understand the mechanism of wheat chromosome translocation.

OsAPL controls the nutrient transport systems in the leaf of rice (Oryza sativa L.).

MAIN CONCLUSION: OsAPL positively controls the seedling growth and grain size in rice by targeting the plasma membrane H+-ATPase-encoding gene, OsRHA1, as well as drastically affects genes encoding H+-coupled secondary active transporters. Nutrient transport is a key component of both plant growth and environmental adaptation. Photosynthates and nutrients produced in the source organs (e.g., leaves) need to be transported to the sink organs (e.g., seeds). In rice, the unloading of nutrients occurs through apoplastic transport (i.e., across the membrane via transporters) and is dependent on the efficiency and number of transporters embedded in the cell membrane. However, the genetic mechanisms underlying the regulation of these transporters remain to be determined. Here we show that rice (Oryza sativa L., Kitaake) ALTERED PHLOEM DEVELOPMENT (OsAPL), homologous to a MYB family transcription factor promoting phloem development in Arabidopsis thaliana, regulates the number of transporters in rice. Overexpression of OsAPL leads to a 10% increase in grain yield at the heading stage. OsAPL acts as a transcriptional activator of OsRHA1, which encodes a subunit of the plasma membrane H+-ATPase (primary transporter). In addition, OsAPL strongly affects the expression of genes encoding H+-coupled secondary active transporters. Decreased expression of OsAPL leads to a decreased expression level of nutrient transporter genes. Taken together, our findings suggest the involvement of OsAPL in nutrients transport and crop yield accumulation in rice.

Genetic Diversity Assessment of the International Maize and Wheat Improvement Center and Chinese Wheat Core Germplasms by Non-Denaturing Fluorescence In Situ Hybridization.

Germplasm is the material basis for crop genetic improvement and related basic research. Knowledge of genetic diversity present in wheat is the prerequisite for wheat breeding and improvement. Non-denaturing fluorescence in situ hybridization (ND-FISH) is a powerful tool to distinguish chromosomal polymorphisms and evaluate genetic diversity in wheat. In this study, ND-FISH using Oligo-pSc119.2-1, Oligo-pTa535-1, and Oligo-(GAA)7 as probes were used to analyze the genetic diversity among 60 International Maize and Wheat Improvement Center (CIMMYT) derived wheat lines, and 93 cultivated wheat and landraces from the Chinese wheat core germplasm. A total of 137 polymorphic FISH patterns were obtained, in which 41, 65, and 31 were from A-, B-, and D-genome chromosomes, respectively, indicating polymorphism of B-genome > A-genome > D-genome. In addition, 22 and 51 specific FISH types were observed in the two germplasm resource lines. Twelve types of rearrangements, including seven new translocations, were detected in all 153 wheat lines. Genetic relationships among 153 wheat lines were clustered into six groups. Our research provides cytological information for rational utilization of wheat germplasm resources.

Identification of QTLs for Stripe Rust Resistance in a Recombinant Inbred Line Population.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating fungal diseases of wheat worldwide. It is essential to discover more sources of stripe rust resistance genes for wheat breeding programs. Specific locus amplified fragment sequencing (SLAF-seq) is a powerful tool for the construction of high-density genetic maps. In this study, a set of 200 recombinant inbred lines (RILs) derived from a cross between wheat cultivars Chuanmai 42 (CH42) and Chuanmai 55 (CH55) was used to construct a high-density genetic map and to identify quantitative trait loci (QTLs) for stripe rust resistance using SLAF-seq technology. A genetic map of 2828.51 cM, including 21 linkage groups, contained 6732 single nucleotide polymorphism markers (SNP). Resistance QTLs were identified on chromosomes 1B, 2A, and 7B; Qyr.saas-7B was derived from CH42, whereas Qyr.saas-1B and Qyr.saas-2A were from CH55. The physical location of Qyr.saas-1B, which explained 6.24-34.22% of the phenotypic variation, overlapped with the resistance gene Yr29. Qyr.saas-7B accounted for up to 20.64% of the phenotypic variation. Qyr.saas-2A, a minor QTL, was found to be a likely new stripe rust resistance locus. A significant additive effect was observed when all three QTLs were combined. The combined resistance genes could be of value in breeding wheat for stripe rust resistance.

Targeted Segment Transfer from Rye Chromosome 2R to Wheat Chromosomes 2A, 2B, and 7B.

Increased chromosome instability was induced by a rye (Secale cereale L.) monosomic 2R chromosome into wheat (Triticum aestivum L.). Centromere breakage and telomere dysfunction result in high rates of chromosome aberrations, including breakages, fissions, fusions, deletions, and translocations. Plants with target traits were sequentially selected to produce a breeding population, from which 3 translocation lines with target traits have been selected. In these lines, wheat chromosomes 2A, 2B, and 7B recombined with segments of the rye chromosome arm 2RL. This was detected by FISH analysis using repeat sequences pSc119.2, pAs1 and genomic DNA of rye together as probes. The translocation chromosomes in these lines were named as 2ASMR, 2BSMR, and 7BSMR. The small segments that were transferred into wheat consisted of pSc119.2 repeats and other chromatin regions that conferred resistance to stripe rust and expressed target traits. These translocation lines were highly resistant to stripe rust, and expressed several typical traits that were associated with chromosome arm 2RL, which are better than those of its wheat parent, disomic addition, and substitution lines that show agronomic characteristics. The integration of molecular methods and conventional techniques to improve wheat breeding schemes are discussed.

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.

A Mutant with Expression Deletion of Gene Sec-1 in a 1RS.1BL Line and Its Effect on Production Quality of Wheat.

The chromosome arm 1RS of rye (Secale cereal L.) has been used worldwide as a source of genes for agronomic and resistant improvement. However, the 1RS arm in wheat has end-use quality defects that are partially attributable to the presence of ω-secalins, which are encoded by genes at the Sec-1 locus. Various attempts in removing the Sec-1 genes from the 1RS.1BL translocation chromosome have been made. In the present study, two new primary 1RS.1BL translocation lines, T917-26 and T917-15, were developed from a cross between wheat variety "A42912" and Chinese local rye "Weining." The lines T917-15 and T917-26 carried a pair of intact and homogeneous 1RS.1BL chromosomes. The line T917-26 also harbored an expression deletion of some genes at the Sec-1 locus, which originated from a mutation that occurred simultaneously with wheat-rye chromosome translocations. These results suggest that the accompanying mutations of the evolutionarily significant translocations are remarkable resources for plant improvement. Comparison of translocation lines with its wheat parent showed improvements in the end-use quality parameters, which included protein content (PC), water absorption (WA), sodium dodecyl sulfate sedimentation (SDSS), wet gluten (WG), dry gluten (DG) and dough stickiness (DS), whereas significant reduction in gluten index (GI) and stability time (ST) were observed. These findings indicate that 1RS in wheat has produced a higher amount of protein, although these comprised worse compositions. However, in the T917-26 line that harbored an expression deletion mutation in the Sec-1 genes, the quality parameters were markedly improved relative to its sister line, T917-15, especially for GI and DS (P < 0.05). These results indicated that expression deletion of Sec-1 genes significantly improves the end-use quality of wheat cultivars harboring the 1RS.1BL translocation. Strategies to remove the Sec-1 genes from the 1RS.1BL translocation in wheat improvement are discussed.

[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.

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.

Alterations and abnormal mitosis of wheat chromosomes induced by wheat-rye monosomic addition lines.

BACKGROUND: Wheat-rye addition lines are an old topic. However, the alterations and abnormal mitotic behaviours of wheat chromosomes caused by wheat-rye monosomic addition lines are seldom reported. METHODOLOGY/PRINCIPAL FINDINGS: Octoploid triticale was derived from common wheat T. aestivum L. 'Mianyang11'×rye S. cereale L. 'Kustro' and some progeny were obtained by the controlled backcrossing of triticale with 'Mianyang11' followed by self-fertilization. Genomic in situ hybridization (GISH) using rye genomic DNA and fluorescence in situ hybridization (FISH) using repetitive sequences pAs1 and pSc119.2 as probes were used to analyze the mitotic chromosomes of these progeny. Strong pSc119.2 FISH signals could be observed at the telomeric regions of 3DS arms in 'Mianyang11'. However, the pSc119.2 FISH signals were disappeared from the selfed progeny of 4R monosomic addition line and the changed 3D chromosomes could be transmitted to next generation stably. In one of the selfed progeny of 7R monosomic addition line, one 2D chromosome was broken and three 4A chromosomes were observed. In the selfed progeny of 6R monosomic addition line, structural variation and abnormal mitotic behaviour of 3D chromosome were detected. Additionally, 1A and 4B chromosomes were eliminated from some of the progeny of 6R monosomic addition line. CONCLUSIONS/SIGNIFICANCE: These results indicated that single rye chromosome added to wheat might cause alterations and abnormal mitotic behaviours of wheat chromosomes and it is possible that the stress caused by single alien chromosome might be one of the factors that induced karyotype alteration of wheat.