Generation and characterisation of monosomic chromosome addition lines of Brassica campestris - B. oxyrrhina

 Monosomic chromosome addition lines of Brassica oxyrrhina in the background of alloplasmic B. campestris carrying B. oxyrrhina cytoplasm were generated and characterised through morphology, cytology and molecular (RAPD) analysis. Four successive backcrosses of the synthetic alloploid B. oxycamp with B. campestris yielded 24 monosomic addition plants that were grouped into seven different synteny groups based on morphological similarity and RAPD patterns. Each synteny group exhibited morphological features diagnostic for the presence of individual B. oxyrrhina chromosomes including some novel phenotypes. Meiotic studies of the addition lines revealed the homoeology of four B. oxyrrhina chromosomes (synteny groups 1, 3, 5 and 6 ) with B. campestris chromosomes as indicated by trivalent associations, with the highest homoeology (44.23%) in synteny group 1 and the lowest (6.1%) in synteny group 3. Seed fertility of the addition lines ranged from 94.85% (synteny group 1) to 56.98% (synteny group 5). All of the addition lines were male-sterile except synteny group 6 which had 12–16% stainable pollen. Ovule transmission of the B. oxyrrhina chromosomes added to the progenies of addition lines ranged from 23.52% (synteny group 6) to 14% (synteny group 7). RAPD analysis confirmed the validity of synteny grouping based on morphological observations. Approximately 45% of the primers studied were informative, giving B. oxyrrhina-specific RAPD bands unique for each synteny group, except group 6. Received: 20 October 1997 / Accepted: 31 March 1998     

Construction of synteny groups of Brassica alboglabra by RAPD markers and detection of chromosome aberrations and distorted transmission under the genetic background of B. campestris

Interspecific hybrids were produced by crosses between the inbred lines of B. campestris and B. alboglabra, and were backcrossed twice to B. campestris. Genetical constitutions of the BC₂ plants were analyzed by RAPD (random amplified polymorphic DNA), flow cytometry and cytological observations. By using 140 arbitrary primers, a total of 137 polymorphic bands were obtained and 125 were found to be specific to B. alboglabra. Based on the presence and absence of the specific RAPD markers of B. alboglabra, 13 synteny groups were constructed. The number of markers in each synteny group was found to be different and varied from 2 to 28. This reflects the difference in the degree of genetic variability among the B. alboglabra chromosomes from those of B. campestris. Losses or gains of RAPD markers were observed frequently in most of the synteny groups, which indicated the occurrence of chromosome translocations and/or deletions in the chromosomes of B. alboglabra. In a population of 40 BC₂ plants, chromosome transmission rates were analyzed by using the RAPD markers in each synteny group. Most of the chromosomes of the synteny groups were transmitted with rates of 0.37–0.68. An extremely high transmission rate, 0.98, was however observed in one of the synteny groups. Inheritance data of the synteny groups revealed relationships among themselves. The plants lacking the RAPD markers of two synteny groups tended to lose others belonging to the rest of the synteny groups, indicating the effects of these groups on the transmission of B. alboglabra chromosomes to the B. campestris background. Received: 26 February 1999 / Accepted: 30 December 1999     

A Brassica campestris-alboglabra addition line and its use for gene mapping,intergenomic gene transfer and generation of trisomics

Summary Brassica campestris-alboglabra monosomic addition lines were developed from a trigenomic Brassica hybrid (2 n=3 x=29, AAC) obtained by backcrossing a resynthesized B. napus (2 n=4 x=38, AACC) line to its parental B. campestris (2 n=2 x=20, AA) line. One addition line was characterized genetically with three loci specific for the alien chromosome and cytologically by meiotic analysis. The following results were obtained. (1) The same chromosome in the B. alboglabra (2 n= 2 x=18, CC) genome carried the three loci, E _c, W _c and Lap-1 C ^c, which control the biosynthesis of erucic acid, white flower colour and the faster migrating band of leucine aminopeptidase, respectively. The linear order and possible positions of the three loci were inferred. The meiotic behaviour of the alien chromosome was documented and its transmission frequency was assessed. (2) Intergenomic recombination frequently occurred in the monosomic addition line, resulting in the introgression of one or two loci from the alien chromosome into the B. campestris genome. (3) B. campestris trisomics were found in the progeny of the monosomic addition line. (4) The removal of the other eight C-genome chromosomes from the trigenomic Brassica hybrid led to a dramatic increase in the erucic acid content of the monosomic addition line. (5) No offspring of the trigenomic Brassica hybrid showed evidence of intergenomic recombination and introgression of the W _c locus into the B. campestris genome. It is questioned whether such a difference might be due to a possible regulating mechanism for homoeologous chromosome pairing.     

Molecular cytogenetic analysis of Brassica rapa-Brassica oleracea var. alboglabra monosomic addition lines

Interspecific alien chromosome addition lines can be very useful for gene mapping and studying chromosome homoeology between closely related species. In this study we demonstrate a simple but robust manner of identifying individual C-genome chromosomes (C5, C8 and C9) in the A-genome background through the simultaneous use of 5S and 25S ribosomal probes on mitotic and meiotic chromosomes of three different Brassica rapa-B. oleracea var. alboglabra monosomic addition lines. Sequential silver staining and fluorescence in situ hybridisation indicated that 18S-5.8S-25S rRNA genes on the additional chromosome C9 are expressed in the A-genome background. Meiotic behaviour of the additional chromosomes was studied in pollen mother cells at diakinesis and metaphase I. In all of the addition lines the alien chromosome was most frequently observed as a univalent. The alien chromosome C5, which carries an intercalary 5S rDNA locus, occasionally formed trivalents that involved either rDNA- or non rDNA-carrying chromosomes from the A genome. In the case of chromosomes C8 and C9, the most frequently observed intergenomic associations involved the regions occupied by 18S-5.8S-25S ribosomal RNA genes. It is possible that not all such associations represent true pairing but are remnants of nucleolar associations from the preceding interphase. Variations in the numbers and distribution of 5S and 25S rDNA sites between cultivars of B. oleracea, B. oleracea var. alboglabra and B. rapa are discussed.This revised version was published online in April 2005 with corrections to Fig. 2.     

Cytology, RAPD, and seed colour of progeny plants from Brassica rapa-alboglabra aneuploids and development of monosomic addition lines.

Progeny plants from Brassica rapa-alboglabra aneuploids were characterized genetically by scoring random amplified polymorphic DNA (RAPD) markers and seed colour and cytologically as to chromosome number and pairing. Sets of RAPD markers specific for each of the encountered eight alien Brassica alboglabra chromosomes were defined. The finding of subsets of markers associated with the presence or absence of alien chromosomes inferred the frequent occurrence of intergenomic genetic recombination and introgression. The chromosome numbers were in the range 2n = 20-28, with a maximum of seven alien B. alboglabra chromosomes and one trisomic B. rapa chromosome. Five types of monosomic addition lines were obtained, two of which have not been developed before. Differences in chromatin condensation patterns made it possible to differentiate between the B. rapa and B. alboglabra chromosomes at diakinesis, and to detect intergenomic homoeological pairing. In addition to the frequent formation of trivalents by homoeologous pairing of an alien B. alboglabra chromosome and a background B. rapa pair, occasional heteromorphic intergenomic bivalents and B. rapa univalents were encountered. Homoeological intergenomic pairing occurred between chromosomes with similar centromeric and karyotypic positions. Plants with structurally changed alien chromosomes were found. The RAPD and cytological data substantiated each other. Observations of the colour of sown and harvested seeds indicated that B. alboglabra chromosome 4 carries a gene for brown seed colour. It exerts its control embryonically, and thus it differs from chromosome 1 which controls seed colour maternally.     

Identification of Brassica oleracea monosomic alien chromosome addition lines with molecular markers reveals extensive gene duplication

Summary Chromosomes of Brassica oleracea (2n=18) were dissected from the resynthesized amphidiploid B. napus Hakuran by repeated backcrosses to B. campestris (2n=20), creating a series of monosomic alien chromosome addition line plants (2n=21). Using morphological, isozyme and restriction fragment length polymorphism markers (RFLPs), 81 putative loci were identified. Of nine possible synteny groups, seven were represented in the 25 monosomic addition plants tested. Sequences homologous to 26% of the 61 DNA clones utilized (80% were cDNA clones) were found on more than one synteny group, indicating a high level of gene duplication. Anomalous synteny associations were detected in four 2n=21 plants. One of these plants showed two markers from one B. oleracea chromosome associated with a second complete B. oleracea synteny group, suggesting translocation or recombination between non-homologous chromosomes in Hakuran or the backcross derivatives. The other three 2n=21 plants each contained two or more B. oleracea synteny groups, suggesting chromosome substitution.     

Identification of wheat-Agropyron cristatum monosomic addition lines by RFLP analysis using a set of assigned wheat DNA probes

A non-radioactive digoxigenin-labelled DNA method was used successfully to identify RFLP markers in 54 Triticum aestivum cv Chinese Spring — Agropyron cristatum (2n=28, genome PPPP) P-genome monosomic addition lines. Southern analysis using a set of 14 DNA probes identifying each homoeologous chromosome arm, combined with two restriction enzymes HindIII and EcoRI, indicated that six A. cristatum chromosomes (1P, 2P, 3P, 4P, 5P and 6P) and five A. cristatum chromosome arms (2PS, 2PL, 5PL, 6PS and 6PL) have been individually added to the wheat genome. The added chromosomes of three lines were Agropyron translocated chromosomes. It was also found that two addition plants possessed an Agropyron-wheat translocation. These results showed that RFLP analysis using the set of assigned wheat probes was a powerful tool in detecting and establishing homoeology of alien A. cristatum chromosomes, or arms, added to wheat, as well as in screening the alien addition material. The creation of the monosomic addition lines should be useful for the transfer of disease-resistance genes from A. cristatum to wheat.     

RAPDs as molecular markers for the detection of Aegilops markgrafii chromatin in addition and euploid introgression lines of hexaploid wheat

 Aegilops markgrafii contains resistance genes to powdery mildew, leaf rust and stripe rust, and also has high crude protein and lysine contents, which can be useful for wheat improvement. These important traits are localized on different chromosomes. Disomic Triticum aestivum-Ae. markgrafii addition lines and euploid introgression lines showing leaf-rust and powdery mildew resistance were screened with RAPDs to detect chromosome-specific markers which can accelerate the breeding process. RAPD markers for all six available disomic addition lines were obtained. The additional chromosomes B, C, D, E, F and G were identified by three, three, three, two, one and seven primers, respectively. All three chromosome-B-specific RAPD markers demonstrated the presence of alien chromatin in the leaf-rust-resistant 42-chromosome introgression lines as well as in the segregating progeny. The three chromosome-C-identifying primers also demonstrated the presence of that chromosome in powdery mildew-resistant euploid introgression lines. The substitution lines (5A)5C and (5D)5C with different genetic backgrounds for both parents, in comparison to the lines mentioned above, showed the chromosome C-specific band with only two of the three primers. The chromosome F-specific primer and a primer evident on all the Ae. markgrafii chromosomes analysed did not generate the expected fragments on the chromosome F_del addition line, indicating that the markers are located on the deleted part of chromosome F. Received: 20 August 1996 / Accepted 17 January 1997     

Development of a complete set of Triticum aestivum-Aegilops speltoides chromosome addition lines

Aegilops speltoides Tausch (2n = 2x = 14, SS) is considered as the closest living relative of the B and G genomes of polyploid wheats. A complete set of Triticum aestivum L. cv Chinese Spring-Ae. speltoides whole chromosomes and seven telosomic addition lines was established. A low pairing accession was selected for the isolation of the chromosome addition lines. Except for chromosomes 3S and 6S, which are presently only available as monosomic additions, all other lines were recovered as disomic or ditelosomic additions. The individual Ae. speltoides chromosomes isolated in the wheat background were assayed for their genetic effects on plant phenotype and cytologically characterized in terms of chromosome length, arm ratio, distribution of marker C-bands, and FISH sites using a Ae. speltoides-specific repetitive element, Gc1R-1, as a probe. The homoeology of the added Ae. speltoides chromosomes was established by using a standard set of RFLP probes. No chromosomal rearrangements relative to wheat were detected. Received: 28 June 1999 / Accepted: 16 November 1999     

Construction of Brassica B genome synteny groups based on chromosomes extracted from three different sources by phenotypic, isozyme and molecular markers

The three B genomes of Brassica contained in B. nigra, B. carinata and B. juncea were dissected by addition in B. napus. Using phenotypic, isozyme and molecular markers we characterized 8 alien B-genome chromosomes from B. nigra and B. carinata and 7 from B. juncea by constructing synteney groups. The alien chromosomes of the three different sources showed extensive intragenomic recombinations that were detected by the presence of the same loci in more than one synteny group but flanked by different markers. In addition, intergenomic recombinations were observed. These were evident in euploid AACC plants of the rapeseed phenotype derived from the addition lines carrying a few markers from the B genome due to translocations and recombinations between non-homoeologous chromosomes. The high plasticity of the Brassica genomes may have been an powerful factor in directing their evolution by hybridization and amphiploidy.     

Characterization of disomic addition lines Brassica napus-Brassica nigra by isozyme,fatty acid,and RFLP markers

Summary Six Brassica napus — B. nigra disomic addition lines were characterized by isozyme, fatty acid, and RFLP markers. The markers were arranged in six synteny groups, representing six of the eight chromosomes present in the B. nigra genome. Synteny group 1 displayed high levels of linoleic and linolenic acids in the seeds of the B. nigra parent. Synteny group 3 accumulated higher levels of eicosenoic and erucic acid than B. nigra. Three of the lines transmitted the alien chromosome to 100% of the progeny. The rest had variable transmission rates but all were above 50%. Most of the lines produced disomic addition plants in their progeny, suggesting pollen transmission of the alien chromosome. In addition to the marked lines, six others remained unmarked. These could be grouped into two classes according to their alien chromosome transmission. It is likely that they represent the two other B. nigra chromosomes that remained uncharacterized by the markers. No diploid individuals carrying B. nigra genome-specific markers were detected in the progenies studied.     

The application of wheat microsatellites to identify disomic Triticum aestivum-Aegilops markgrafii addition lines

 We describe the use of wheat microsatellites for the discrimination of Aegilops markgrafii chromosomes. Twenty out of eighty eight wheat microsatellites (WMS) tested were able to distinguish Triticum aestivum-Ae. markgrafii addition lines. Six, three, three, one and six of 18 WMS can be used as markers for single Ae. markgrafii chromosomes B, C, D, F and G, respectively. Addition line A is not available but additional bands, appearing only in Ae. markgrafii and the T. aestivum-Ae. markgrafii amphiploid and not in any of the available addition lines, indicate that three WMS detect markers for Ae. markgrafii chromosomes A. Addition line E could not be detected by any of the WMS markers applied, although the 20 WMS represented all the homologous groups of wheat. All three WMS located on the short arm of group-2 chromosomes were located on Ae. markgrafii chromosome B; three of four WMS, located on the long arm of wheat group-2 chromosomes, were specific to Ae. markgrafii chromosome G and three of four WMS, specific to group-5 chromosomes, were markers for Ae. markgrafii chromosome C, indicating the homoeology of these wheat chromosome arms with the respective Ae. markgrafii chromosomes. Received: 29 May 1997 / Accepted: 10 September 1997     

Thinopyrum distichum addition lines: production,morphological and cytological characterisation of 11 disomic addition lines and stable addition-substitution line

Plants of the partial amphiploid Inia 66/Thinopyrum distichum (2n = 70)//Inia 66 (2n = 56) were used as male parents in crosses with the monosomic series in the common wheat cultivar Inia 66. The genome and homoeologous group of the monosomic used in the cross affected the distribution of chromosome number of the progeny plants in the F₂ and F₄. Meiosis in the pollen mother cells of the B₁F₇ partial amphiploids was not stable, and not different from that of the B₁F₁ in which univalents and multivalents were observed. Disomic addition lines were selected on the basis of morphology and meiotic stability in the F₂, F₄ and F₅. Eleven of the fourteen possible wheat-Th. distichum disomic addition lines were identified using chromosome C-band pattern, as well as size and arm ratio, as genetic markers. Addition of T. distichum chromosome J ^dll produced a phenotype indicating homoeology with wheat group-2 chromosomes. Clear indications of homoeology based on morphological characteristics were not obtained in any of the other addition lines, probably due to the mixed homoeology of the Th. distichum chromosomes relative to wheat. The addition lines were all susceptible to leaf rust, unlike the germplasm-line Indis which carries a leaf rust resistance gene on a translocation segment derived from Th. distichum. Instability of meiotic pairing was observed in all addition lines. The stability, or not, of progeny chromosome counts did not reflect the level of chromosome pairing instability in the parental plants. SDS-PAGE for gliadin-type seed proteins revealed two addition lines which expressed seed storage proteins uncommon to Inia 66 but typical of Th. distichum.     

Identification of the different Brassica nigra chromosomes from both sets of B. oleracea-B. nigra and B. napus-B. nigra addition lines with a special emphasis on chromosome transmission and self-incompatibility

 The F₁ hybrids produced after crosses between B. gra and B. oleracea were backcrossed two or three times to B. oleracea. Among the 14 plants analysed, five were monosomic addition lines (2n=19), six were double monosomic addition lines (2n=20) and three had three or four additional chromosomes. From these lines, 14 isozyme and 80 RAPD loci were localized on the eight chromosomes of B. nigra. The comparison between B. napus-B. nigra, from which five B. nigra chromosomes were already described, and the new set of B. oleracea-B. nigra addition lines was performed using five isozyme and 22 common RAPD loci. The homology of the common RAPD loci was confirmed by hybridization of the two sets of addition lines as well as the presence of duplicated loci on different chromosomes. For the five added chromosomes available on the two genetic backgrounds, i.e. B. napus and B. oleracea, using isozyme markers, the chromosome transmission rate was studied from backcross progeny using the recurrent parent either as male or as female and from the selfing of monosomic addition lines. For each chromosome, no difference was detected between male and female transmission except for chromosome 3. This latter presented a percentage of female transmission of around 20%, close to the ones observed for the other chromosomes, but a very low male transmission (1.3%). The analysis from restriction enzyme digests of PCR products, obtained from primers selected in highly conserved regions of self-incompatible genes, suggested that the chromosome 3 probably carried the SLG-B. nigra locus. Received: 25 September 1996 / Accepted: 18 October 1996     

Molecular and cytogenetic characterization of an Oryza officinalis–O. sativa chromosome 4 addition line and its progenies

The wild species Oryza officinalis Wall. ex Watt (2n = 24, CC) is a valuable genetic resource for rice (O. sativa L., 2n = 24, AA) breeding and genomics research. Genomic in situ hybridization (GISH) and molecular approaches were used to determine the nature and composition of the additional chromosome in a monosomic alien addition line (MAAL) of O. officinalis and its backcross progenies. The extra wild species chromosome in the MAAL (2n = 2x = 25) was a mosaic one, comprising of the long arm of chromosome 4 from O. officinalis and the short arm from O. sativa. Comparative analysis showed that O. sativa and O. officinalis shared high synteny of restriction fragment length polymorphism (RFLP) markers and low synteny of simple sequence repeat (SSR) markers. A DNA methylation alteration was revealed at C619 in the MAAL and progenies. Analysis of progenies of the MAAL indicated that introgression segments were small in size and introgression was not evenly distributed along the long arm. One recombination hot spot between C513 and RG177 was identified, which is in a gene-rich region.     

Comparison of wheat physical maps with barley linkage maps for group 7 chromosomes

Comparative genetic maps among the Triticeae or Gramineae provide the possibility for combining the genetics, mapping information and molecular-marker resources between different species. Dense genetic linkage maps of wheat and barley, which have a common array of molecular markers, along with deletion-based chromosome maps of Triticum aestivum L. will facilitate the construction of an integrated molecular marker-based map for the Triticeae. A set of 21 cDNA and genomic DNA clones, which had previously been used to map barley chromosome 1 (7H), were used to physically map wheat chromosomes 7A, 7B and 7D. A comparative map was constructed to estimate the degree of linkage conservation and synteny of chromosome segments between the group 7 chromosomes of the two species. The results reveal extensive homoeologies between these chromosomes, and the first evidence for an interstitial inversion on the short arm of a barley chromosome compared to the wheat homoeologue has been obtained. In a cytogenetically-based physical map of group 7 chromosomes that contain restriction-fragment-length polymorphic DNA (RFLP) and random amplified polymorphic DNA (RAPD) markers, the marker density in the most distal third of the chromosome arms was two-times higher than in the proximal region. The recombination rate in the distal third of each arm appears to be 8–15 times greater than in the proximal third of each arm where recombination of wheat chromosomes is suppressed.     

Inheritance of isozyme and RFLP markers in Brassica campestris and comparison with B. oleracea

Summary Using primarily cDNA restriction fragment length polymorphism markers (RFLPs) previously located to Brassica oleracea (cabbage, 2n=18) chromosomes, we initiated a comparative RFLP map in an F₂ population of B. campestris (turnip x mock pak-choi, 2n=20). As with B. oleracea, the genome of B. campestris showed extensive gene duplication, and the majority of detected duplicated loci were unlinked. Only 6 of the 49 identified loci were represented as a single copy, and 3 of these 6 were clustered on a single linkage group showing a distorted segregation ratio. Comparison with B. Oleracea indicates this synteny is conserved between species. Two other linkage groups also appeared syntenic between B. oleracea and B. campestris. One single copy locus appears to have changed synteny between B. oleracea and B. campestris. These observations suggest that B. oleracea and B. campestris share a common ancestor, but that chromosome repatterning has occurred during or after speciation. Within B. campestris, 5 loci appeared duplicated in one parent or the other, and 2 of these were linked. Differentiation through subspecies-specific duplication or deletion events is suggested as one mechansim for the evolution of numerous morphotypes within each of these species.     

Recombination of Solanum brevidens chromosomes in the second backcross generation from a somatic hybrid with S. tuberosum

Solanum brevidens synteny groups were examined with 47 widely-distributed RFLP markers in 17 BC₂ progeny from six fertile BC₁ plants. The BC₁ plants were derived from a single S. brevidens + S. tuberosum somatic hybrid backcrossed with S. tuberosum (potato). Probes which were linked in potato and tomato were also found to be syntenic along each of the 12 S. brevidens chromosomes. More than half of the S. brevidens synteny groups had lost one or more S. brevidens-specific RFLPs in the BC₂, suggesting that recombination had occurred. For 8 of the 12 S. brevidens RFLP synteny groups, the frequency of recombinant chromosomes exceeded that of intact parental chromosomes. Using the RFLP data, 161 RAPD markers were tentatively located throughout the S. brevidens genome. Further analyses with 39 of these 161 RAPD markers generally showed that RAPD and RFLP results were comparable, but some inconsistencies were noted with 14 of the 39 RAPD markers. The extent of marker loss and the high frequency of synteny groups which were marked by a single S. brevidens-specific RFLP marker suggest that the S. brevidens chromosomes have some pairing affinity with potato chromosomes. This interaction should facilitate the transfer of novel disease-resistance traits into potato breeding lines. One plant was recovered with the chromosome number of S. tuberosum (2n=48) that carried a single S. brevidens RFLP marker, suggesting transfer of this S. brevidens marker into the genome of S. tuberosum.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable     

Genetic control of a novel series of trypsin inhibitors in wheat and its relatives

The aneuploids of Chinese Spring wheat have been used to locate the genes(Ti-2) coding for a novel series of trypsin inhibitors to the long arms of the homoeologous group 5 chromosomes. Three allelic variants at the 5D locus were detected in a limited survey among wheat varieties, but no variation at the loci on either chromosome 5A or chromosome 5B was detected. Homoeoloci were found in a number of alien relatives, and in the majority of cases, these were present on the group 5 homoeologue. However, inAegilops umbellulata, theTi-U2 locus was located on a chromosome presumed to belong to homoeologous group 1. NoHordeum vulgare orH. chilense Ti-2 gene was expressed in a wheat background. This new marker will be especially useful as a screening mechanism for nullisomy of chromosome 5B in work aimed at introgression of alien chromatin into wheat.The Agricultural Genetics Company is thanked for financial support.     

Identification of molecular markers linked to Pm13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat

 RFLP, RAPD, STS and DDRT-PCR techniques were applied to find molecular markers linked to Pm13, an Aegilops longissima gene conferring resistance to powdery mildew in wheat. The experimental strategy was based on the differential comparison of DNAs from common wheat and from common wheat/Ae. longissima recombinant lines carrying short segments of the 3S ^l S chromosome arm containing the Pm13 gene. Sixteen RFLP clones that detect loci previously located in the short arms of group-3 wheat chromosomes were screened for their ability to hybridise to Ae. longissima restriction fragments derived from the 3S ^l S segments introgressed into the recombinant lines. Eight RFLP clones and one STS marker detected 3S ^l S-specific fragments whose location relative to the wheat-alien chromatin breakage point of the recombinant lines was determined. Four amplification products were identified through the screening of about 200 RAPD primers. Their polymorphism was associated with the introgression of the alien DNA. One of the differential fragments was derived from the 3S ^l S DNA segment, while the remaining three corresponded to the replaced 3DS DNA. Further analyses carried out using 40 combinations of DDRT-PCR primers detected an additional reproducible polymorphism associated with the presence of 3S ^l S DNA. In view of their possible utilisation in Pm13 marker-assisted selection, differentially amplified RAPD and DDRT-PCR fragments were cloned, transformed into RFLP markers and converted into STS markers. Received: 23 March 1998 / Accepted: 5 August 1998