Rye Translocation Research Articles

Physical mapping of 5S rDNA reveals a new locus on 3R and unexpected complexity in a rye translocation used in chromosome mapping.

Using fluorescence in situ hybridization (FISH) with probe pScT7, three different 5S rDNA loci were detected in the satellite of rye chromosome 1R (5SDna-R1) and in the short arms of chromosomes 3R (5SDna-R3) and 5R (5SDna-R2) respectively. All three loci showed polymorphism for the hybridization signal intensity. In order to determine the localization of these rye 5S rDNA multigene loci with higher precision within the corresponding chromosome arms, the probe pScT7 was physically mapped by FISH in relation to the following five translocations (Wageningen Tester Set): T850W (1RS/4RL), T248W (1RS/6RS), T273W (1RS/5RL), T305W (2RS/5RS) and T240W (3RS/5RL). Accurate physical maps of the translocation breakpoints had previously been made using electron microscope analysis of spread pachytene synaptonemal complexes of heterozygotes for the different translocations. The results indicate that locus 5SDna-R3 is located between the breakpoint of translocation T240W and the telomere, whereas locus 5SDna-R2 is located between the breakpoint of translocation T305W and the centromere, the hybridization of probe pScT7 on T305W translocated chromosomes demonstrating the complex nature of this translocation. On the other hand, the simultaneous detection of probes pScT7 and pTA71 (18S-5.8S-26S rDNA) with two different fluorochromes, indicated that the breakpoints of translocations T850W and T248W are located between loci Nor-R1 and 5SDna-R1.

The glutenin fraction of wheat protein: The importance of genetic background on its quantity and quality

AbstractThe influence of high‐molecular‐weight glutenin subunits on the properties of the gel‐protein fraction of glutenin proteins in wheat was determined on 20 varieties grown in the 1989 UK Recommended List trials. Both the presence of subunit 1 (chromosome 1A) and the 1B/1R rye translocation were shown to influence gel‐protein weight and breakdown rate during mixing. The gel‐protein tests were correlated with CBP (Chorleywood Bread Process) loaf volume, but they did not add anything to the correlation between Glu‐1 score and loaf volume. Both gel‐protein tests indicated that phenotypic variation could be almost as large as genotypic variation. Breakdown rate was able to detect the abnormal properties of Pastiche (weak) and Fresco (extra‐strong) that were not observed using established quality tests such as the sodium dodecylsulphate sedimentation volume.

Characterization of the 1B/1R translocation in wheat using water extractable protein concentrate

An electrophoretic procedure was developed to obtain patterns of water soluble proteins from the endosperm halves of seeds to detect the 1B/1R translocation in wheat cultivars. The water soluble proteins were precipitated with Coomassie Brilliant Blue R-250 and separated in a 10% polyacrylamide gel with sodium dodecyl sulfate. This procedure extracted protein bands (Mr 40,000, 44,000 and 45,000) corresponding to the ω-secalins of the rye parent which were present only in the wheat cultivars carrying 1B/1R translocation. By simplifying extract preparation and providing clear band resolution this procedure facilitates large scale screening of wheat lines for the rye translocation. Proteins with properties of overlapping solubilities are also discussed.

Direct fluorochrome-labeled DNA probes for direct fluorescent in situ hybridization to chromosomes.

AbstractChromosomal in situ hybridization enables determination of the presence and location of DNA sequences complementary to a labeled probe along chromosomes and within interphase nuclei. The use of directly fluorochrome-labeled probes means that sites of probe hybridization can be directly visualized. Lengthy detection procedures, as in the indirect immunochemistry methods to detect biotin or digoxigenin, are not needed. However, because there is no signal amplification, sensitivity is limited and the system is used mostly to detect middle- to high-copy number (Fig. 1) or pooled probes, although antibody amplification of some fluorochrome labels is possible (1), and then the method must be evaluated in comparison with digoxigenin (chapter 27) or biotin (chapter 25). Direct fluorescent double in situ hybridization to a partial metaphase of a hexaploid wheat variety carrying a rye translocation (1B/1R). (A) Bright fluorescence of the rye chromosome arms probed with rhodamine-labeled total genomic DNA from rye after green excitation (arrow heads), with the wheat chromosomes fluorescing weakly. (B) Strong fluorescence of the fluorescein-labeled rDNA under blue excitation. rDNA sites can be distinguished on several wheat chromosomes (arrows) and the two rye arms (open arrows). Bar = 10 µm. KeywordsPropidium IodideHybridization MixtureStringent WashFluorochrome LabelPool ProbeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

A rapid technique for the detection of wheat–rye translocation chromosomes

After 1–2 days on nitrocellulose filters kept moist with Tris–NaCl–EDTA (TNE) solution, sufficient DNA is adsorbed from individual half seeds of wheat to allow rye heterochromatin sequences to be detected in the adsorbed samples. Using the probe pSchet1, seeds of rye (Secale cereale), triticale (× Triticosecale), wheat (Triticum aestivum), and wheat containing 1RS/1BL translocation chromosomes have been successfully screened for the presence or absence of this heterochromatin sequence. The system has the potential to recognise the presence of the short arm of chromosome 1R of rye, and the presence of other rye DNA sequences, in thousands of samples per week.Key words: wheat, 1RS/1BL translocation, rye, heterochromatin, pSchet1

Genetic control of 1R nucleolus organizer region expression in the presence of wheat genomes

The expression of rRNA genes located in the nucleolar organizing region (NOR) present on the short arm of chromosome 1R from rye (Secale cereale L.) was examined in several hexaploid (Triticum aestivum L.) and tetraploid wheats (Triticum turgidum L.) containing the entire chromosome 1R from rye (disomic substitution 1B(1R)), its full haploid genome (hexaploid wheat–rye F1 hybrid), or only its short arm translocated to the long arms of wheat chromosomes from the homoeologous group 1 (disomic translocations 1AL/1RS, 1BL/1RS, or 1DL/1RS) or added to the complete hexaploid wheat genotype (monotelosomic addition 1RS). By silver staining and determination of the number of Ag-NORs and the average number of nucleoli per root-tip cell it became apparent that the expression of 1R NORs, in the presence of wheat genomes, depends on the absence of the long arm of rye chromosome 1R. In wheat-rye F1 hybrids and in hexaploid wheat with a disomic substitution 1B(1R), 1R NOR was morphologically absent, even when only one wheat major NOR was present, in contrast with its frequent expression in wheat–rye translocation or addition lines where only its short arm was added. It is suggested that wheat nucleolar dominance over rye as expressed by heterochromatic and silent NOR in 1RS is under a complex genetic control which involves interaction between 1RL and unidentified wheat genes.Key words: 1R nucleolus organizer region, gene activity, amphiplasty.

Contributions of protein fractions to dough handling properties of wheat-rye translocation cultivars

Fractionation and reconstitution studies have been undertaken to assess the contribution of various flour components to dough stickiness and mixing properties, comparing rye translocation lines with their recurrent parents. For one line, approximately one third the stickiness originated in the water-soluble fraction and about two thirds in the gluten and, for another line, contributions from these two fractions each accounted for about half the stickiness. Reduction in the amount of water solubles below their natural level in the reconstituted flours improved Mixogram properties and decreased stickiness score. Similarly, dough stickiness was reduced by addition of flour protein fractions concentrated in glutenin proteins. When gluten was separated into two roughly equal fractions by differential solubility in dilute HCl, interchange experiments established that the difference in their effects on stickiness could be almost wholly attributed to the soluble portion. SE-HPLC revealed that the acid-soluble fraction from the translocation line SUN 89D had a lower proportion of glutenin than that of its parent Cook, whereas the HPLC profiles of the two acid-insoluble fractions were similar. SDS-PAGE analysis of protein fractions indicated that water-soluble and gluten acid-soluble fractions of translocation lines contained most of the rye secalins. The interchange experiments suggest that the weak and sticky dough properties of the translocation lines arise from a shift in the balance of the proportions of polymeric and monomeric proteins. This was supported by experiments in which this balance was varied by addition of specific protein fractions.

The tolerance of wheat to high temperatures during reproductive growth. III. Booting to anthesis

A range of Australian and overseas wheat cultivars was grown in the naturally lighted glasshouses of the Canberra phytotron, with a standard day/night temperature regime of 18/1 3�C. Grain number per main culm ear under these standard conditions was compared with the response obtained when sets of plants were transferred to high temperature (24/19�C, or 30/25�C) over the period from flag leaf ligule to ear emergence (booting), or from ear emergence to the end of anthesis (pollination and fertilization).Some Australian lines such as Isis and Hybrid Titan were tolerant of high temperature at booting, while others such as Pinnacle and Olympic showed a marked sensitivity to high temperature at this stage. Cultivars from the Middle East and tropical areas were generally more tolerant of high temperature at booting than cultivars from regions such as North America and Europe, while the Australian lines were intermediate in their response. With the cultivar Pinnacle, it was shown that at least part of the low fertility associated with high temperature at booting was related to poor pollen development. Commencing the high temperature treatment earlier in the development of the ear and continuing this until ear emergence resulted in adaptation in the cultivar H757 from Afghanistan, which showed an increase in grain set above that of the short high temperature booting treatment. However, this contrasted with the response of the cultivar Banks when the extended high temperature treatment resulted in a further reduction, not an increase in grain set. It was shown that the presence of the rye translocation for rust resistance (1B/1R) in near isogenic lines of Condor resulted in reduced sensitivity to high temperature. This would suggest that species such as rye should be examined more closely for their sensitivity to environmental stress.Exposure to high temperature only during anthesis generally had a small effect oil grain set. Some cultivars showed an increase in grain set, whereas others showed a decrease. Part of this variation may be related to the finding that under high temperature conditions, high humidity (v.p.d. 6.7 mb) could reduce grain set. However, given the normal relation between temperature and humidity in Australia, this effect is likely to be limited to glasshouse conditions.

Rye heterochromatin. II. Characterization of a derivative from chromosome 1DS.1RL with a reduced amount of the major repeating sequence

Homoeologous recombination between wheat chromosomes and the long arm of chromosome 1R of rye present in a wheat background as the wheat–rye translocation, 1DS.1RL, has been reported. During the course of this study an unexpected plant (308-17), with a recombinant phenotype, arose from a control population where homoeologous pairing was thought to be suppressed. The putative recombinant chromosome in plant 308-17 carried two seed protein loci located on 1RL (namely, the rye Glu-R1 locus and a recently discovered globulin-like marker) but appeared to lack C-banded heterochromatin. Further investigation of this apparent recombinant chromosome in progeny of 308-17 using a cloned probe for the 350 family of rye heterochromatic sequence indicated that some terminal heterochromatin was still present but in a much reduced amount. Because it appears that only the terminal region has been changed, the modified chromosome in 308-17 most likely did not arise from homoeologous recombination but rather from some form of heterochromatin loss event, possibly involving an unequal sister chromatid exchange within the terminal heterochromatin of 1RL. Sister lines to plant 308-17 carrying Glu-R1 contained a normal amount of 1RL heterochromatin.Key words: rye–wheat, heterochromatin, recombinant, unequal sister chromatid exhange.

Identification of the chromosomes of the rye translocation tester set

Intercrossing the Wageningen translocation tester set of rye and the series of 'Imperial' rye additions to 'Chinese Spring' wheat of Sears yielded 29 chromosome disomic translocation hybrids. Observation of trivalents led to the identification of the chromosomes of the tester set in terms of the terminology system used in the Triticinae. The analysis was complicated by very low chiasma frequencies in some short chromosome segments in the hybrids. Nevertheless, it could be safely concluded that 1R=VII; 2R=III; 3R=II; 4R=IV; 5R=VI; 6R=V; 7R=I, which deviates slightly from previous classifications based on other methods.

Sources of tertiary trisomics for balanced chromosomal systems in hybrid rye breeding

To increase the efficiency of isolating tertiary trisomics, five rye translocations of the Wageningen translocation tester set with exchanged segments of different size were crossed with either a telocentric or a primary trisomic, or with each other. Progenies of two telocentric translocation trisomics, four translocation trisomics, and one double-translocation trisomic thus obtained, were karyotyped, and metaphase I (MI) configurations of the two telocentric translocation trisomics were quantitatively investigated. Tertiary trisomics were obtained with the extra, short translocation chromosome of each of the five interchanges, at frequencies of 0.5–1.0% in the case of the telocentric translocation trisomics. This hardly implies an increase compared with the corresponding interchange heterozygous disomics (maximum 1%, tertiary and translocation trisomics combined). The translocation and double-translocation trisomics yielded higher percentages of tertiary trisomics, the difference being due to the extra chromosome (telocentric or normal) present in the mother plants, and to different ranges of possibilities for MI association and anaphase I (AI) disjunction, respectively. No tertiary trisomics carrying a long translocation chromosome as the extra chromosome were detected. A reduced viability of eggs or zygotes with large amounts of extra chromosomal material, rather than a low frequency of the appropriate MI orientation, is suggested to be the cause.

Physiologic Differentiation of Wheat Stem Rust on Rye

Five self-fertile lines of Secale cereale possessing single genes conferring resistance to stem rust were successfully used to differentiate between strains of Puccinia graminis tritici. In an earlier study four of these lines were shown to differentiate between Australian cultures of P. graminis secalis. Gene H transferred from Wrens-5 rye to one of the five lines appears to be identical with gene Sr27 in Acosta's wheat-Imperial rye translocation stock WRT 238.5.