Controlled introgression to wheat of genes from rye chromosome arm 1RS by induction of allosyndesis

Summary Chromosome pairing between rye chromosome arm 1RS, present in two wheat-rye translocation stocks, and its wheat homoeologues was induced by introducing the translocations into either a ph1bph1b or a nullisomic 5B background. This rye arm carries a gene conferring resistance to wheat stem rust, but lines carrying the translocation produce a poor quality dough unsuitable for breadmaking. Storage protein markers were utilised along with stem rust reaction to screen for allosyndetic recombinants. From a 1DL-1RS translocation, three lines involving wheat-rye recombination were recovered, along with thirteen lines derived from wheat-wheat homoeologous recombination. From a 1BL-1RS translocation, an additional three allosyndetic recombinants were recovered. Nullisomy for chromosome 5B was as efficacious as the ph1b mutant for induction of allosyndesis, and the former stock is easier to manipulate due to the presence of a 5BL-encoded endosperm protein. The novel wheat-rye chromosomes present in the recombinant lines may enable the rye disease resistance to be exploited without the associated dough quality defect.     

Pairing and recombination between individual chromosomes of wheat and rye in hybrids carrying the ph1b mutation

Wheat-rye chromosome associations at metaphase I studied by Naranjo and Fernández-Rueda (1991) in ph1b ABDR hybrids have been reanalysed to establish the frequency of pairing between individual chromosomes of wheat and rye. Wheat chromosomes, except for 2A and 2D, and their arms were identified by C-banding. Diagnostic C-bands and other cytological markers such as telocentrics or translocations were used to identify each one of the rye chromosomes and their arms. Both the amount of telomeric C-heterochromatin and the structure of the rye chromosomes relative to wheat affected the level of wheatrye pairing. The degree to which rye chromosomes paired with their wheat homoeologues varied with each of the three wheat genomes; in most groups, the B-R association was more frequent than the A-R or D-R associations. Recombination between arms 1RL and 2RL and their homoeologues of wheat possessing a different telomeric C-banding pattern was detected and quantified at anaphase I. The frequency of recombinant chromosomes obtained supports the premise that recombination between wheat and rye chromosomes may be estimated from wheat-rye pairing.     

The effect of ph mutations on homoeolgous pairing in hybrids of wheat with Triticum longissimum

Homoeologous pairing at metaphase-I was analyzed in wild-type, ph2b, and ph1b hybrids of wheat and a low-pairing type of T. longissimum in order to study the effect of ph mutations on the pairing of T. longissimum chromosomes with wheat chromosomes. Chromosomes of both species, and their arms, were identified by C-banding. The three types of hybrids, with low-, intermediate-, and high-pairing levels, respectively, exhibited a very similar pairing pattern which was characterized by the existence of two types, A-D and B-S¹, of preferential pairing. These results confirm that the S¹ genome of T. longissimum is closely related to the B genome of wheat. The possible use of ph1b and ph2b mutations in the transfer to wheat of genes from related species is discussed.     

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.     

小麦ph1b突变体与小黑麦杂交的细胞遗传学研究

本文利用普通小麦品系"中国春"(对照)、中国春ph1b突变体分别与八倍体小黑麦、六倍体小黑麦杂交,杂种F1的减数分裂前期Ⅰ染色体行为表现异常,中期Ⅰ出现较多的单价体、棒状二价体和多价体,在后期和末期出现落后染色体、染色体片断和微核。原因是ph1b基因的存在造成染色体联会机制紊乱,致使一些部分同源染色体配对并发生互换,有可能在以后的世代产生染色体易位与基因重组。     

Some characteristics of crossing over in induced recombination between chromosomes of wheat and rye

Allopolyploid wheat (Triticum aestivum L.) carries three pairs of homoeologous genomes but its meiotic pairing is diploid-like. This is the effect of the Ph (pairing homoeologous) system which restricts chromosome pairing to strictly homologous. Ph1 is the locus with the strongest effect. Disabling Ph1 permits pairing between homoeologues and is routinely used in chromosome engineering to introgress alien variation into breeding stocks. Whereas the efficiency of Ph1 and the general pattern of homoeologous crossovers in its absence are quite well known from numerous studies, other characteristics of such crossovers remain unknown. This study analyzed the crossover points in four sets of the ph1b-induced recombinants between wheat homologues as well as between three wheat and rye (Secale cereale) homoeologous chromosome arms, and compared them to crossovers between homologues in a reference wheat population. The results show the Ph1 locus also controls crossing over of homologues, and the general patterns of homologous (with Ph1) and homoeologous (with ph1b) crossing over are the same. In all intervals analyzed, homoeologous crossovers fell within the range of frequency distribution of homologous crossovers among individual families of the reference population. No specific DNA sequence characteristics were identified that could be recognized by the Ph1 locus; the only difference between homologous and homoeologous crossing over appears to be in frequency. It is concluded that the Ph1 locus likely recognizes DNA sequence similarity; crossing over is permitted between very similar sequences. In the absence of Ph1 dissimilarities are ignored, in proportion to the level of the sequence divergence.     

Chromosome structure of Triticum longissimum relative to wheat

Homoeologous pairing at meiotic metaphase I was analyzed in T. longissimum x T. aestivum hybrids in order to reconfirm the homoeologous relationships of T. longissimum chromosomes to wheat. Hybrids between T. longissimum and Chinese Spring carrying the Ph1 gene or theph1b mutation, which showed low and high pairing levels, respectively, were used. Chromosome arms associated at metaphase I were identified by C-banding. The homoeology of chromosomes 1S ^l , 2S ^l , 3S ^l , 5S ^l and 6S ^l to wheat group 1,2, 3, 5, and 6 chromosomes, respectively, was confirmed. Chromsome arms 4S ^l S and 7S ^l S showed normal homoeologous relationships to wheat. The 4S ^l L arm carries a translocated segment from 7S ^l L relative to wheat. The 7S ^l L arm seldom paired, likely because this arm lost a relatively long segment and received a very short segment in the interchange with 4S ^l L. Available data suggest that translocation 4S ^l L/7S ^l L arose in the evolution of T. longissimum, which implies that this species was not the donor of the B genome of wheat.     

Production of wheat-barley recombinant chromosomes through induced homoeologous pairing

Summary Sears' phlb mutant was used successfully for the first time to induce pairing and recombination between specific barley chromosomes and their wheat homoeologues. Pairing was induced in specially constructed genetic stocks having 19 pairs of wheat chromosomes and triply monosomic for either barley chromosome arm 6HL or 3HL, a related wheat chromosome, and chromosome 5B of wheat carrying the phlb mutation. Wheat-barley recombinant chromosomes were isolated from among the progeny obtained from self-fertilization of the triple monosomic stocks, by screening for dissociation of biochemical markers on the barley arms. Glutamic oxaloacetic transaminase (GOT), aconitase hydratase (ACO), and dipeptidase (DIP) isozymes were used to select recombinants involving the 6HL arm, and esterase (EST) and malate dehydrogenase (MDH) were used for the 3HL arm. Altogether, six recombinants involving 6HL (1.4%) and six involving 3HL (1.1%) were isolated. These wheat-barley recombinant chromosomes are being used to construct a detailed gene order map of barley based on biochemical and molecular markers.     

Relationships of Agropyron intermedium chromosomes determined by chromosome pairing and alcohol dehydrogenase isozymes in common wheat background

Summary The relationships of Agropyron intermedium chromosomes in two wheat-Agropyron addition series were determined. Chromosome pairing behaviour revealed that the alien chromosome in lines TAF-2 and L7 of Vilmorin-A. intermedium set are homologous to the alien chromosomes in lines P and C of the Caribo-A. intermedium set respectively. Localization of alcohol dehydrogenase isozyme genes in Vilmorin-Agropyron addition line L4 and in Caribo-Agropyron line O indicated relationships with wheat chromosomes of homoeologous group 4.     

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     

Homoeologous relationships of Aegilops speltoides chromosomes to bread wheat

 Homoeologous pairing at metaphase I was analysed in the standard-type, ph2b and ph1b hybrids of Triticum aestivum (AABBDD) and Aegilops speltoides (SS). Data from relative pairing affinities were used to predict homoeologous relationships of Ae. speltoides chromosomes to wheat. Chromosomes of both species, and their arms, were identified by C-banding. The Ae. speltoides genotype carried genes that induced a high level of homoeologous pairing in the three types of hybrids analyzed. All arms of the seven chromosomes of the S genome showed normal homoeologous pairing, which implies that no apparent chromosome rearrangements occurred in the evolution of Ae. speltoides relative to wheat. A pattern of preferential pairing of two types, A-D and B-S, confirmed that the S genome is very closely related to the B genome of wheat. Although this pairing pattern was also reported in hybrids of wheat with Ae. longissima and Ae. sharonensis, a different behaviour was found in group 5 chromosomes. In the hybrids of Ae. speltoides, chromosome 5B-5S pairing was much more frequent than 5D-5S, while these chromosome associations reached similar frequencies in the hybrids of Ae. longissima and Ae. sharonensis. These results are in agreement with the hypothesis that the B genome of wheat is derived from Ae. speltoides. Received: 8 January 1998 / Accepted: 4 February 1998     

Isolation and characterization of wheat-rye recombinants involving chromosome arm 1DS of wheat

Summary The introgression of genetic material from alien species is assuming increased importance in wheat breeding programs. One example is the translocation of the short arm of rye chromosome 1 (1RS) onto homoeologous wheat chromosomes, which confers disease resistance and increased yield on wheat. However, this translocation is also associated with dough quality defects. To break the linkage between the desirable agronomic traits and poor dough quality, recombination has been induced between 1RS and the homoeologous wheat arm IDS. Seven new recombinants were isolated, with five being similar to those reported earlier and two havina new type of structure. All available recombinantsw ere characterized with DNA probes for the loci Nor-R1, 5SDna-R1, and Tel-R1. Also, the amount of rye chromatin present was quantified with a dispersed rye-specific repetitive DNA sequence in quantitative dot blots. Furthermore, the wheat-rye recombinants were used as a mapping tool to assign two RFLP markers to specific regions on chromosome arms 1DS and 1RS of wheat and rye, respectively.     

Biochemical evidence of a translocation between 6 RL/7 RL chromosome arms in rye (Secale cereale L.). A genetic map of 6R chromosome

Summary The segregation of different isozymic loci was investigated in backcrosses and F₂s in rye. The leucin aminopeptidase-1 (Lap-1), Aconitase-1 (Aco-1), Esterase-6 (Est-6), Esterase-8 (Est-8), and Endopeptidase-1 (Ep-1) loci were linked. The Aco-1, Est-6, and Est-8 loci have been previously located on the 6RL chromosome arm. The Lap-1 locus has been located on the 6RS chromosome arm. The results favor the gene order: Lap-1... (centromere)... Aco-1... Est-8... Est-6... Ep-1. The isoelectric focusing separations of aqueous extracts from mature embryo tissue of wheat-rye addition and substitution lines involving the chromosomes of cereal rye Secale cereale L. confirmed the gene location of locus Ep-1 on the 6RL chromosome arm. Screening of wheat-rye addition lines involving the chromosomes of Secale montanum revealed that Ep-1 locus is not located on chromosome 6R of S. montanum. These results are the first biochemical evidence of the translocation between chromosome arms 6RL/7RL in the evolution of S. cereale from S. montanum.     

Chromosome pairing relationships among the A,B, and D genomes of bread wheat

Summary Chromosome pairing and chiasma frequency were studied in bread wheat euhaploids (2n = 3x = 21; ABD genomes) with and without the major pairing regulatorPh1. This constitutes the first report of chromosome pairing relationships among the A, B, and D genomes of wheat without the influence of an alien genome. AllPh1 euhaploids had very little pairing, with 0.62–1.05 rod bivalents per cell; ring bivalents were virtually absent and mean arm-binding frequency (c) values ranged from 0.050 to 0.086. In contrast, theph1b euhaploids had extensive homoeologous pairing, with chiasma frequency 7.5–11.6 times higher than that in thePh1 euhaploids. They had 0.53–1.16 trivalents, 1.53–1.74 ring bivalents, and 2.90–3.57 rod bivalents, withc from 0.580 to 0.629. N-banding of meiotic chromosomes showed strongly preferential pairing between chromosomes of the A and D genomes; 80% of the pairing was between these genomes, especially in the presence of theph1b allele. The application of mathematical models to unmarked chromosomes also supported a 21 genomic structure of theph1b euhaploids. Numerical modeling suggested that about 80% of the metaphase I association was between the two most related genomes in the presence ofph1b, but that pairing under Ph1 was considerably more random. The data demonstrate that the A and D genomes are much more closely related to each other than either is to B. These results may have phylogenetic significance and hence breeding implications.This paper is dedicated to the memory of the late Ernest R. SearsCooperative investigations of the USDA-Agricultural Research Service and the Utah Agricultural Experiment Station, Logan, UT 84322, USA. Approved as Journal Paper No. 3986     

Identification of a complete set of isogenic wheat/rye D-genome substitution lines by means of Giemsa C-banding

Summary A complete set of isogenic wheat/rye D-genome substitutions were produced by crossing an inbred line of spring rye Secale cereale L. cv. Prolific to a tetraploid wheat, the A-and B-genomes of which had previously been extracted from hexaploid wheat, Triticum aestivum L. em Thell. cv. Thatcher. After chromosome doubling, the derived hexaploid triticale (x Triticosecale Wittmack) was backcrossed to 6x Thatcher and selection for wheat/rye substitution lines was carried out in BCF₃ to BCF₆ families by using Giemsa C-banding. Five fertile disomic wheat/rye D-genome substitution lines were obtained and their chromosomal constitution was determined to be 1D/1R, 2D/2R, 7D/4R, 6D/6R, 7D/7R. The two remaining 3R and 5R substitutions are at the moment in a monosomic condition. Another 1D/7R substitution was detected but this plant was very weak and sterile, indicating that only substitutions between homoeologous chromosomes result in fertile, vigorous plants. Furthermore, many rye telocentrics as well as rye-rye and rye-wheat translocations were selected. Since all lines selected in this program share the same genetic background of Thatcher wheat, genetic heterogeneity is excluded. The material is very useful, therefore, for analyzing the effects of different rye chromosomes or chromosome segments in an otherwise homozygous background.Contribution No. 797     

A comparison of physical distribution of recombination in chromosome 1R in diploid rye and in hexaploid triticale

Summary Polymorphism for six C-bands on chromosome 1R was used to study the frequency and distribution of recombination along the chromosome in a diploid rye (Secale cereale L.) and in a hexaploid triticale (X Triticosecale Wittmack) derived from it. In rye, the total recombination frequency in five segments of chromosome 1R was 93.7%. Recombination was concentrated in the distal regions of both chromosome arms and was infrequent in the proximal regions. In hexaploid triticale the total recombination frequency in the same chromosome was reduced to 51.7%. In both backgrounds the distal half of the long arm showed similar recombination frequencies, 51.4% and 45.7% for rye and triticale, respectively. The remaining about two-thirds of the chromosome length showed 42.3% recombination in rye but only 6% recombination in triticale. The results demonstrate that the genetic background in which mapping is performed not only affects the total amount of recombination, but also its distribution along the chromosome length.     

Distribution of genes and recombination on wheat homoeologous group <Emphasis Type="Italic">6</Emphasis> chromosomes: a synthesis of available information

Presence of genes in gene-rich regions on wheat chromosomes has been widely reported. However, there is a lack of information on the precise characterization of these regions with respect to the distribution of genes and recombination. We attempted to critically analyze the available data to characterize gene-rich regions and to study the distribution of genes and recombination on wheat homoeologous group 6 chromosomes which are a reservoir of several useful genes controlling traits of economic importance. Consensus physical and genetic linkage maps were constructed for homoeologous group 6 using physical and genetic mapping data. Five major gene-rich regions were identified on homoeologous group 6 chromosomes, with two on the short and three on long arm. More than 90% of marker or gene loci were present in these five gene-rich regions, which comprise about 30% of the total physical chromosomal length. The gene-rich regions were mainly present in the distal 60% regions of the chromosomes. About 61% of the total loci map in the most distal regions which span only about 4% of the physical length of the chromosome. A range of sub-microscopic regions within each gene-rich region were also identified. Comparisons of the consensus physical and genetic linkage maps revealed that recombination occurred mainly in the gene-rich regions. Seventy percent of the total recombination occurred in the two most distally located regions that span only 4% of the physical length of the chromosomes. The relationship of recombination to the gene-rich region is not linear with distance from the centromere, especially on the long arm. The kb/cM estimates for group 6 chromosomes ranged from 146 kb in the gene-rich to about 10 Mb in the gene-poor region. The information obtained here is vital in understanding wheat genome structure and organization, which may lead in developing better strategies for positional cloning in wheat and related cereals.This revised version was pubished online in April 2005 with corrections to the page numbering.     

Determination of the frequency of wheat-rye chromosome pairing in wheat x rye hybrids with and without chromosome 5B

Genomic in-situ hybridization (GISH) was used to determine the amount of wheat-rye chromosome pairing in wheat (Triticum aestivum) x rye (Secale cereale) hybrids having chromosome 5B present, absent, or replaced by an extra dose of chromosome 5D. The levels of overall chromosome pairing were similar to those reported earlier but the levels of wheat-rye pairing were higher than earlier determinations using C-banding. Significant differences in chromosome pairing were found between the three genotypes studied. Both of the chromosome-5B-deficient hybrid genotypes showed much higher pairing than the euploid wheat hybrid. However, the 5B-deficient hybrid carrying an extra chromosome 5D had significantly less wheat-rye pairing than the simple 5B-deficient genotype, indicating the presence of a suppressing factor on chromosome 5D. Non-homologous/non-homoeologous chromosome pairing was observed in all three hybrid genotypes. The value of GISH for assessing the level of wheat-alien chromosome pairing in wheat/alien hybrids and the effectiveness of wheat genotypes that affect homoeologous chromosome pairing is demonstrated.     

Determination of ergot alkaloids in rye and rye flour

An effective and timesaving analytical method was developed for the determination of 12 ergot alkaloids (ergometrine, ergotamine, ergocristine, α-ergokryptine, ergosine, ergocornine, and their respective -inine isomers) in rye and rye flour. Samples were extracted with dichloromethane/ethyl acetate/methanol/aqueous ammonia (25%) (50/25/5/1, v/v/v/v), and extracts were purified using a basic alumina column. The eluate was dried in the nitrogen stream and redissolved in acetonitrile/ ammonia carbamate-buffer (0.2 g/1), (1/1, v/v), and injected into an HPLC-FLD system (λ_Ex 330 nm, λ_Em 415 nm), using the same mixture as mobile phase and a Phenyl-Hexyl column. Detection limits for the individual compounds ranged from 0.01 μg/kg to 0.5 μg/kg. In sample material spiked with a mixture of these compounds at two different levels (13 μg/kg and 27 μg/kg per compound), mean (n=5) recoveries were at 101% (s_r 6.4%) and 89% (s_r 3.1%), respectively. Presented at the 28th Mykotoxin-Workshop, Bydgoszcz, Poland, May 29–31, 2006     

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.