Homoeology of rye chromosome arms to wheat

Summary Cytological markers such as diagnostic C-bands, telocentrics, and translocations were used to identify the arms of rye chromosomes associated with wheat chromosomes at metaphase I in ph1b mutant wheat × rye hybrids. Arm homoeologies of rye chromosomes to wheat were established from the results of metaphase I pairing combined with available data on the chromosomal location of homoeoloci series in wheat and rye. Only arms 1RS, 1RL, 2RL, 3RS, and 5RS showed normal homoeologous relationships to wheat. The remaining arms of rye appeared to be involved in chromosome rearrangements that occurred during the evolution of the genus Secale. We conclude that a pericentric inversion in chromosome 4R, a reciprocal translocation between 3RL and 6RL, and a multiple translocation involving 4RL, 5RL, 6RS, and 7RS are present in rye relative to wheat.     

Rye chromosome translocations in hexaploid wheat: a re-evaluation of the loss of heterochromatin from rye chromosomes

Summary Using in situ hybridization techniques, we have been able to identify the translocated chromosomes resulting from whole arm interchanges between homoeologous chromosomes of wheat and rye. This was possible because radioactive probes are available which recognize specific sites of highly repeated sequence DNA in either rye or wheat chromosomes. The translocated chromosomes analysed in detail were found in plants from a breeding programme designed to substitute chromosome 2R of rye into commercial wheat cultivars. The distribution of rye highly repeated DNA sequences showed modified chromosomes in which (a) most of the telomeric heterochromatin of the short arm and (b) all of the telomeric heterochromatin of the long arm, had disappeared. Subsequent analyses of these chromosomes assaying for wheat highly repeated DNA sequences showed that in type (a), the entire short arm of 2R had been replaced by the short arm of wheat chromosome 2B and in (b), the long arm of 2R had been replaced by the long arm of 2B. The use of these probes has also allowed us to show that rye heterochromatin has little effect on the pairing of the translocated wheat arm to its wheat homologue during meiosis. We have also characterized the chromosomes resulting from a 1B-1R translocation event.From these results, we suggest that the observed loss of telomeric heterochromatin from rye chromosomes in wheat is commonly due to wheat-rye chromosome translocations.     

Amplification of repeated DNA sequences in wheat X rye hybrids regenerated from tissue culture

Summary Previous C-banding analysis of wheat (Triticum aestivum)X rye (Secale cereale) hybrids regenerated from tissue culture revealed enlarged C-bands in some rye chromosomes, but the molecular nature of the change was not determined. In situ hybridization using two DNA probes containing repeated sequences from rye telomeric heterochromatin was conducted on these wheatX rye hybrids and their progeny to investigate the occurrence of amplification in repeated sequences. Clones pSC 74 and pSC 119, which contain sequences from the 480-bp and 120-bp repeated DNA families of rye, respectively, were used as probes. Amplification of 480-bp repeated sequences in the short arm telomere of chromosome 7R was detected in three wheatxrye hybrids and their progeny. The amplified 480-bp sequences were detected by an enlarged hybridization site for pSC 74 at the 7RS telomere, and by the appearance at this same telomeric site of an unlabeled, blue chromosome segment in an otherwise completely brown chromosome hybridizing entirely to the biotin-labeled pSC 119 probe. This variant form of chromosome 7R was not observed in several Chaupon plants, or in the other hybrids derived from the same embryos, indicating the origin of the change in tissue culture. The amplified sequences were inherited up to at least three generations. Deletions and translocations were also observed.Contribution No. 87-9-J, Kansas Agricultural Experiment Station, Kansas State University     

The genetic and molecular characterization of pollen-derived plant lines from octoploid triticale x wheat hybrids

Six doubled-haploid (DH) lines, derived by anther culture from octoploid triticale x wheat hybrids, were characterized using cytological, biochemical and molecular techniques. Lines varied in their wheat and rye genome composition, and were either wheat-rye chromosome multiple addition lines or had spontaneous substitutions and/or wheat-rye translocations. Most of the lines contained a pair of 4R chromosomes, whereas 1R or 7R were present in others. The results are similar to those previously obtained with hexaploid triticale x wheat crosses and indicate that it is possible to produce alien (wheat/rye) addition, substitution, and translocation lines directly from the anther culture of intergeneric hybrids.     

非Robertsonian类型小黑麦易位系的研究

非Robertsonian类型小黑麦易位系的研究@胡含$中国科学院遗传研究所植物细胞与染色体工程国家重点实验室!北京100101小黑麦;;易位系     

八倍体小黑麦×普通小麦杂种后代群体中的染色体易位

用改良的Giemsa C-带技术以单株为基础分析了八倍体小黑麦×普通小麦的杂种BC_1,F_(?)和F_(?)代植株的核型。在鉴定了C-带核型的1098株杂种后代植株中,发现了78条小麦-黑麦和277条黑麦-黑麦易位染色体。在不同的世代和株系中,小麦-黑麦染色体易位率变化在4.35—14.07%之间,平均7.10%;黑麦-黑麦染色体易位率在0.48—52.78%之间,平均25.23%。鉴定的小麦-黑麦易位染色体涉及了黑麦的14条不同的染色体臂和小麦的A、B和D组染色体。易位的48.57%发生在小麦和黑麦的部分同源染色体之间,51.43%发生在非部分同源染色体之间。不同的黑麦染色体臂参与易位的频率不同。小麦-黑麦染色体易位主要发生在杂种的早期世代,使用适当的选择技术在F_3获得了纯合的易位植株。文中讨论了快速选育易位系的技术和它们在小麦育种中的应用问题。     

小麦遗传背景对黑麦抗叶锈基因Lr26的抗性表达的影响

利用1套从小麦纯系和黑麦自交系培育出的1R附加系、代换系和易位系,研究了1RS上的抗叶锈基因Lr26在小麦中的表达。结果发现,1R二体附加系和纯合1RS/1BL易位系高抗小麦叶锈病;而其小麦亲本、1R(1B)代换系和1BS/1RL易位系重感叶锈病。这一结果指出了黑麦染色体臂1RS上的抗小麦叶锈病基因Lr26在小麦中的表达受小麦染色体臂1BL上的基因的强烈影响,指出了外源基因在小麦中的表达可受染色体臂或基因水平上的相互作用的制约。文中讨论了外源基因与小麦遗传背景相互作用在小麦育种中的意义。     

Molecular cytogenetic analysis of radiation-induced wheat-rye terminal and intercalary chromosomal translocations and the detection of rye chromatin specifying resistance to Hessian fly

Radiation-induced wheat-rye chromosome translocation lines resistant to Hessian fly, Mayetiola destructor (say), were analyzed by in situ hybridization using total genomic and highly repetitive rye DNA probes pSc119 and pSc74. In situ hybridization analysis revealed the exact locations of the translocation breakpoints and allowed the estimation of the sizes of the transferred rye segments. T6BS·6BL-6RL and T4BS· 4BL-6RL are terminal translocations with either most of the complete long arm of rye chromosome 6R or only the distal 57% of the 6RL arm attached to the long arms of wheat chromosomes 6B and 4B, respectively. The breakpoint in T6BS·6BL-6RL is located at a fraction length (FL) of 0.11 in the long arm of T6BS 6BL-6RL and at FL 0.46 in the long arm of T4BS·4BL-6RL. Ti4AS·4AL-6RL-4AL is an intercalary translocation with the breakpoint located at FL 0.06 in the long arm of wheat chromosome 4A. The inserted 6RL segment, with the Hessian fly resistance gene, has a size of 0.7 m, and is the smallest and, so far, the first radiation-induced intercalary translocation identified in wheat.by R. Apples     

The centromere structure in Robertsonian wheat-rye translocation chromosomes indicates that centric breakage-fusion can occur at different positions within the primary constriction

Univalent chromosomes at meiotic metaphase I have a tendency to misdivide at the centromeres. Fusion of the misdivision products may produce Robertsonian translocations. The fine structure of the centromeres in Robertsonian wheat-rye translocation chromosomes was analyzed by fluorescence in situ hybridization (FISH) using two centromere-specific DNA clones: pRCS1, derived from rice, and pAWRC1, derived from rye. Clone pRCS1 hybridizes to the centromeres of all grasses including wheat and rye, whereas clone pAWRC1 is rye specific and hybridizes only to the centromeres of rye. Four of the six wheat-rye translocations derived from a single centric misdivision event (1st generation translocations) had hybrid centromeres, with approximately half of the centromere derived from rye and half from wheat. In the two other 1st generation translocations, the entire centromere was derived from rye. Among eight reconstructed wheat and rye chromosomes that originated from two consecutive centric misdivision-fusion events (2nd generation translocations), T1BS.1BL (derived from T1BS.1RL and T1RS.1BL) and one of three T2BS.2BL (derived from T2RS.2BL and T2BS.2RL) had hybrid centromeres. T1RS.1RL (derived from T1BS.1RL and T1RS.1BL), two of three T2BS.2BL, and all three T2RS.2RL (derived from T2RS.2BL and T2BS.2RL) had rye centromeres. All three 3rd generation translocations had hybrid centromeres with approximately half of the centromere derived from rye. There were no indications that the composite structure of the centromere in these chromosomes affected their behavior in mitosis or meiosis. These observations support the notion of a compound structure of the centromere in higher organisms, and indicate that during the centric breakage-fusion event, centromere breakage may occur in different positions along the segment of the chromosome that interacts with the spindle fibers. Normal behavior of the 1st, 2nd, and 3rd generation centric translocations in mitosis and meiosis indicates that, at least in wheat and rye, centromeres are not chromosome specific.     

The mapping of highly-repeated DNA families and their relationship to C-bands in chromosomes of Secale cereale

The relationship between the chromosomal location of heterochromatin C-bands and of four non-homologous repeated sequence families constituting 8 to 12% of total rye DNA has been investigated in chromosomes of rye (Secale cereale) by in situ hybridisation. Three rye varieties, a set of rye disomic additions to wheat and a triticale were studied. Only centromeric and nucleolar organizer region (NOR) associated C-bands failed to display hybridisation to at least one of the sequences and many telomeric blocks of heterochromatin contained all four repeated sequence families. Both between-variety differences in the chromosomal distribution of repeated sequences, and intravarietal heterozygosities were frequently noted and are probably widespread. — Previously reported deletions of heterochromatin from King II rye chromosomes added to the Holdfast wheat complement were correlated with deletions of some, but not all, of the highly repeated sequence families. A previously unreported loss of some families from King II rye chromosome 4R/7R in a Holdfast wheat genetic background was detected. This loss was not associated with complete deletion of a C-band. A deletion has also probably occurred from the short arm telomere of 4R/7R in the triticale variety Rosner. It is suggested that the families of repeats in rye telomeric heterochromatin which are absent from wheat are selected against in the wheat genetic background.     

Visualization of Secale cereale DNA in wheat germ plasm by fluorescent in situ hybridization

Homozygous wheat/rye (1BL/1RS or 1AS/ 1RL) translocation lines have significantly contributed to wheat production, and several other wheat/rye translocation lines show a potential promise against biotic and abiotic stresses. Detecting the presence of rye at the chromosome level is feasible by C-banding and isozyme protocols, but the diagnostic strength of genomic in situ hybridization for eventually analyzing smaller DNA introgressions has greater significance. As a first step we have applied the genomic in situ hybridization technique to detect rye chromosomes in a wheat background using germ plasm of agricultural significance. By this method rye contributions to the translocations 1BL/1RS, 1AL/1RS, 5AS/5RL and 6BS/6RL could be identified. Differential labelling has further enabled the detection of rye and Thinopyrum bessarabicum chromosomes in a trigeneric hybrid of Triticum aestivum/Th. bessarabicum//Secale cereale.     

小麦基因组中外源染色体片段的检测和小麦基因分子标记的建立

小麦基因组中外源染色体片段的检测和小麦基因分子标记的建立@石锐$哈尔滨师范大学生物系!150080小麦;;外源染色体;;分子标记     

利用杀配子染色体2C诱导中国春-黑麦二体附加系染色体畸变的研究

将中国春-黑麦(1R-7R)二体附加系与中国春-2C(Aegilops cylindrica)二体附加系杂交,获得F1,对F1体细胞染色体进行C分带鉴定和花粉母细胞减数分裂行为的观察与分析,发现减数分裂行为异常。对自交获得的430株F2进行单株染色体C分带和荧光原位分子杂交鉴定,检测到易位、缺失、等臂染色体、双着丝点染色体等染色体畸变类型。此外还检测到2C与小麦2A、2B、2D染色体的二体或单体自发代换系。杂交F。染色体畸变的规律与频率如下：研究共得到含黑麦染色体的变异22株,变异频率为5,1％。其中含黑麦染色体的易位系为10株,占2,3％;缺失12株,占2．79％;黑麦的等臂染色体3株,占O．7％。易位染色体既有含小麦着丝点的(大部分),也含有黑麦着丝点的(仅1例)。黑麦的染色体畸变中,发生于不同同祖群的频率不同,1R为5个,2R为3个;3R为1个;4R为3个;5R为6个;6R为4个。易位多为端部易位。共鉴定出小麦的缺失系54株,其中A基因组有27个,占6.27％;B基因组有20个,占4,65％;D基因组有7个,占1.66％。对杀配子染色体对小麦及黑麦不同同祖群染色体作用的差异性及作用特点进行了探讨。     

Preferential elimination of chromosome 5R of rye in the progeny of 5R5D dimonosomics

Transmission of chromosome 5R of rye (Secale cereale L.) and chromosome 5D of common wheat (Triticum aestivum L.) through gametes of 5R5D dimonosomics (2n = 42, 20W″ + 5R′ + 5D′) was studied. Chromosome 5R was found to have lower competitiveness as compared to 5D. Gametes with the rye chromosome were two times less often involved in the formation of a progeny. The combined frequency of the karyotypes of wheat (5D5D) and wheat monosomics (5D) was 11.6-fold higher than the frequency of the karyotypes of substitution lines (5R5R) and monosomics for the rye chromosome (5R). The karyotypes of 10.38% of hybrid plants had aberrant 5R chromosomes with different translocations formed as a result of breakages in the centromere and in the proximal region of the long arm. Telocentrics for the short arm t5RS, i5RS isochromosomes, and chromosomes with a terminal deletion T5RS.5RL-del were identified. The absence of amplification of SSR markers mapped on 5RS and the detection of PCR products for a number of 5RL markers (including the genome-specific rye marker Xrms115) permitted nine plants carrying only the long arm of chromosome 5R to be revealed. Since t5RL telocentrics were not detected by the cytological analysis, the results obtained allow us to suggest the presence of small intercalary translocations of the long arm of chromosome 5R in chromosome 5D or in other wheat chromosomes.     

New wheat-rye 5DS-4RS·4RL and 4RS-5DS·5DL translocation lines with powdery mildew resistance

Powdery mildew is one of the serious diseases of wheat (Triticum aestivum L., 2n = 6 × = 42, genomes AABBDD). Rye (Secale cereale L., 2n = 2 × = 14, genome RR) offers a rich reservoir of powdery mildew resistant genes for wheat breeding program. However, extensive use of these resistant genes may render them susceptible to new pathogen races because of co-evolution of host and pathogen. Therefore, the continuous exploration of new powdery mildew resistant genes is important to wheat breeding program. In the present study, we identified several wheat-rye addition lines from the progeny of T. aestivum L. Mianyang11 × S. cereale L. Kustro, i.e., monosomic addition lines of the rye chromosomes 4R and 6R; a disomic addition line of 6R; and monotelosomic or ditelosomic addition lines of the long arms of rye chromosomes 4R (4RL) and 6R (6RL). All these lines displayed immunity to powdery mildew. Thus, we concluded that both the 4RL and 6RL arms of Kustro contain powdery mildew resistant genes. It is the first time to discover that 4RL arm carries powdery mildew resistant gene. Additionally, wheat lines containing new wheat-rye translocation chromosomes were also obtained: these lines retained a short arm of wheat chromosome 5D (5DS) on which rye chromosome 4R was fused through the short arm 4RS (designated 5DS-4RS·4RL; 4RL stands for the long arm of rye chromosome 4R); or they had an extra short arm of rye chromosome 4R (4RS) that was attached to the short arm of wheat chromosome 5D (5DS) (designated 4RS-5DS·5DL; 5DL stands for the long arm of wheat chromosome 5D). These two translocation chromosomes could be transmitted to next generation stably, and the wheat lines containing 5DS-4RS·4RL chromosome also displayed immunity to powdery mildew. The materials obtained in this study can be used for wheat powdery mildew resistant breeding program.     

Detection of interchromosomal translocations within the Triticeae by RFLP analysis.

Twenty-three wheat/alien addition or substitution lines were screened using restriction fragment length polymorphisms for the presence or absence of 4/5 and 4/7 reciprocal translocations in the alien chromosomes. Such translocations have previously been identified in wheat and rye. Group 4 and group 5 Aegilops umbellulata, Triticum urartu, and Thinopyrum bessarabicum chromosomes were found to carry 4/5 translocations. Evidence for a 4/7 translocation was also found in Secale montanum. The presence of the 4/5 translocations in T. urartu indicates that the translocation predates the polyploidization of wheat. The implications of these results are discussed.     

Induction of small-segment-translocation between wheat and rye chromosomes

A new approach to produce wheat-rye translocation, based on the genetic instability caused by monosomic addition of rye chromosome in wheat, is described. 1 283 plants from the selfed progenies of monosomic addition lines with single chromosome of inbred rye line R12 and complete chromosome complement of wheat cultivar Mianyang 11 were cytologically analyzed on a plant-by-plant basis by the improved C-banding technique. 63 of the plants, with 2n = 42, were found containing wheat-rye translocation or substitution, with a frequency of 4. 91% . Compared with the wheat parent, other 32 plants with 2n = 42 exhibited obvious phenotypic variation, but their com-ponent of rye chromosome could not be detected using the C-banding technique. In situ hybridization with a biotin-la-beled DNA probe was used to detect rye chromatin and to determine the insertion sites of rye segments in the wheat chromosomes. In 20 out of the 32 variant wheat plants, small segments of rye chromosomes were found being inserted into dif     

Single nucleotide polymorphic marker enabling rapid and early screening for the homoeolocus of β-amylase-R1: a gene linked to copper efficiency on 5RL

This study describes the development of a PCR marker to detect the β-amylase-R1 gene of rye. It provides an easy and rapid means for the identification of plants containing the β-amylase-R1. Because rye chromosome segments do not normally recombine with wheat chromosomes, this marker provides a means for tracking all linked genes on that alien 5RL chromosome segment. Reaction conditions were optimised for an annealing temperature of 60°C for a high stringency. The reaction was also optimised for low reaction volumes reducing the cost of the reagents required for the reaction. This PCR test can be used in breeding or mapping programs for the rapid screening of progeny containing translocations of 5RL and hence select for the copper efficiency trait of rye.     

Physical distribution of translocation breakpoints in homoeologous recombinants induced by the absence of the Ph1 gene in wheat and triticale

The physical distribution of translocation breakpoints was analyzed in homoeologous recombinants involving chromosomes 1A, 1B, 1D of wheat and 1R of rye, and the long arms of chromosome 7S of Aegilops speltoides and 7A of wheat. Recombination between homoeologues was induced by removal of the Ph1 gene. In all instances, translocation breakpoints were concentrated in the distal ends of the chromosome arms and were absent in the proximal halves of the arms. The relationship between the relative distance from the centromere and the relative homoeologous recombination frequency was best explained by the function f(x)=0.0091e^0.0592x. The pattern of recombination in homoeologous chromosomes was essentially the same as in homologues except that there were practically no double exchanges. Among 313 recombinant chromosomes, only one resulted from a double crossing-over. The distribution of translocation breakpoints in translocated arms indicated that positive chiasma interference operated in homoeologous recombination. This implies that the reduction of the length of alien chromosome segments present in translocations with wheat chromosomes may be more difficult than the production of the original recombinants.     

Chromosome composition of wheat-rye lines and the influence of rye chromosomes on disease resistance and agronomic traits

Identification of the chromosomal composition of common wheat lines with rye chromosomes was carried out using genomic in situ hybridization and 1RS- and 5P-specific PCR markers. It was demonstrated that wheat chromosomes 5A or 5D were substituted by rye chromosome 5R in the wheat-rye lines. It was established that one of the lines with complex disease resistance contained rye chromosome 5R and T1RS.1BL, while another line was found to contain, in addition to T1RS.1BL, a new Robertsonian translocation, T5AS.5RL. Substitution of the wheat chromosome 5A with the dominant Vrn-A1 gene for the Onokhoiskaya rye chromosome 5R led to lengthening of the germination-heading period or to a change in the type of development. A negative influence of T1RS.1BL on SDS sedimentation volume and grain hardness was demonstrated, along with a positive effect of the combination of T1RS.1BL and 5R(5D) substitution on grain protein content. Quantitative traits of the 5R(5A) and 5R(5D) substitution lines were at the level of recipient cultivars. A line with two translocations, T1RS.1BL + T5AS.5Rl, appeared to be more productive as compared to the line carrying T1RS.1BL in combination with the 5R(5D) substitution.