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  • 1
    ISSN: 1432-2242
    Keywords: Key words Barley ; Microsatellites ; Linkage map ; Genetic similarity (GS) ; Polymorphism information content (PIC)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  By searching the EMBL DNA sequence database, we were able to develop 39 new, database-derived barley microsatellites. Eighteen of these EMBL microsatellites were mapped either to the interspecific barley map Lerche×BGRC41936 (L×41), the Igri×Franka map (I×F, Graner et al. 1991), or to both maps simultaneously. In addition, all 39 EMBL microsatellites were assigned to individual barley chromosomes by PCR screening of wheat barley addition lines. Both studies verified a random distribution of the microsatellites within the barley genome. Subsequently, 22 EMBL microsatellites were used to assess the genetic similarity among a set of 28, mainly German, barley cultivars and two wild form accessions. Spring and winter cultivars could be easily differentiated using the first coordinate of a principal coordinate analysis. Whereas the group of spring barley cultivars appeared rather homogeneous, winter barley cultivars could be divided into three subgroups. Two H. v. ssp. spontaneum accessions were included in the assessment of genetic similarity. They were placed among the winter barley cultivars. Based on the assessment of the 30 barley cultivars and accessions, the polymorphism information content (PIC) of each EMBL microsatellite has been calculated. The average PIC value among the EMBL microsatellites was equal to 0.38, which ascertains the value of these microsatellites as a genetic tool in barley genome research projects.
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  • 2
    ISSN: 1432-2242
    Keywords: Tomato ; TMV resistance ; RFLP ; High resolution map ; YAC contig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With the ultimate goal of cloning the Tobacco Mosaic Virus (TMV) resistance gene Tm-2a from tomato by means of positional cloning, a high-resolution map of a 4.3-cM region surrounding the Tm-2a gene has been constructed. In total, 13 RFLP and RAPD markers were mapped in close proximity to Tm-2a using 2112 individuals from an intraspecific Lycopersicon peruvianum backcross. The closest flanking markers were separated from Tm-2a by 0.05 cM on each side. Only one marker, the cDNA clone R12, co-segregated with Tm-2a. In order to physically cover the Tm-2a region, R12 and the flanking DNA marker TG207 were used to select homologous YAC clones. To-date, two YAC-contigs spanning approximately 340 kb and 360 kb have been constructed. The data obtained from these experiments indicate that recombination around the centromere of chromosome 9 is extremely suppressed.
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  • 3
    ISSN: 1432-2242
    Keywords: Bolting gene ; Vernalization requirementBeta vulgaris L. ; RFLP markers ; Penetrance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The annual habit in beet is due to complete or partial absence of the vernalization requirement and can cause severe problems in the beet crop. The absolute vernalization requirement in beet is controlled by a major geneB (bolting), known to be linked to the geneR (red hypocotyl color), in linkage group I. Segregation for theB andR genes was studied in several beet progenies. Penetrance of the annual habit inBb genotypes was affected by both environmental and genetic factors. The precise location in linkage group I of the major geneB was found by restriction fragment length polymorphism (RFLP) analysis in a back-cross progeny exhibiting partial penetrance of the annual habit. The linkage value betweenB andR was in good accordance with previous estimations. Use of the closest RFLP marker (pKP591: 3.8 recombination units) allowed us to estimate the penetrance of the annual habit in this back-cross as 0.62. Evidence of pseudo-compatibility was found in the wild coastal beet (Beta vulgaris sspmaritima) used as the mother plant of the back-cross: the selfing rate was estimated as 7%.
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  • 4
    ISSN: 1432-2242
    Keywords: Key words Tomato ; TMV resistance ; RFLP ; High resolution map ; YAC contig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With the ultimate goal of cloning the Tobacco Mosaic Virus (TMV) resistance gene Tm-2a from tomato by means of positional cloning, a high-resolution map of a 4.3-cM region surrounding the Tm-2a gene has been constructed. In total, 13 RFLP and RAPD markers were mapped in close proximity to Tm-2a using 2112 individuals from an intraspecific Lycopersicon peruvianum backcross. The closest flanking markers were separated from Tm-2a by 0.05 cM on each side. Only one marker, the cDNA clone R12, co-segregated with Tm-2a. In order to physically cover the Tm-2a region, R12 and the flanking DNA marker TG207 were used to select homologous YAC clones. To-date, two YAC-contigs spanning approximately 340 kb and 360 kb have been constructed. The data obtained from these experiments indicate that recombination around the centromere of chromosome 9 is extremely suppressed.
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  • 5
    ISSN: 1432-2242
    Keywords: Sugar beet ; Beta vulgaris ; RFLP markers ; Linkage map ; Distorted segregation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have established a first linkage map for beets based on RFLP, isozyme and morphological markers. The population studied consisted of 96 F2 individuals derived from an intraspecific cross. As was expected for outbreeding species, a relatively high degree of polymorphism was found within sugar beet; 47% of the DNA markers were polymorphic for the chosen population. The map consists of 115 independent chromosomal loci designated by 108 genomic DNA probes, 6 isozyme and one morphological marker. The loci cover 789 cM with an average spacing of 6.9 cM. They are dispersed over nine linkage groups corresponding to the haploid chromosome number of Beta species. Eighteen markers (15.4%) showed distorted segregation which, in most instances, can be explained by gametic selection of linked lethal loci. The application of the linkage map in sugar beet breeding is discussed.
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  • 6
    ISSN: 1432-2242
    Keywords: Restriction fragment length polymorphism ; Linkage map ; Hordeum vulgare ; Double haploids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to construct an RFLP map of barley, two populations were analyzed using 251 genomic and cDNA markers: one population comprised 71 F1 antherderived double haploid (DH) individuals of an intraspecific cross (IGRI x FRANKA), and the other 135 individuals of an interspecific F2/F3 progeny (VADA x H. spontaneum). The distribution of nonrepetitive clones over the seven barley chromosomes revealed a maximum for chromosome 2H and a minimum for 6H. The polymorphism of the interspecific progeny (76%) clearly exceeded that of the intraspecific progeny (26%) although, based on their pedigrees, IGRI and FRANKA are only distantly related. The contribution of individual chromosomes of the DH parents to the overall polymorphism varied between 8% and 50%. A significant portion (44% versus 10% of the interspecific progeny) of the markers mapped on the DH offspring showed distorted segregation, caused mainly by the prevalence of variants originating from the parent that better responded to in vitro culture (IGRI). In contrast to the interspecific map, probes displaying skewed segregation were clustered on the DH map on discrete segments. The colinear arrangement of both maps covers a distance of 1,453 cM and identifies regions of varying map distances.
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  • 7
    ISSN: 1432-2242
    Keywords: Sugar beet ; Beta species ; DNA “finger-printing” ; Cluster analysis ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Forty-one accessions of the genusBeta representing wild and cultivated species of all sections were analyzed by DNA “fingerprinting”. Four sugar beet minisatellite DNA probes revealed characteristic banding patterns with Southern-hybridizedBeta DNA restricted withHindIII. A total of 111 polymorphic RFLP bands were scored across all accessions. Cluster analysis based on genetic similarity estimates for all 820 combinations of accessions revealed the following results. (1) All accessions could unambiguously be identified by a characteristic RFLP banding pattern. (2) The sugar beet cultivars examined displayed a low level of genetic diversity; they showed high similarity toB. Vulgaris ssp.maritima but low genetic similarity to the other wild species of section I. (3) In most cases, the present taxonomic classification of the genusBeta was confirmed. Species of sections II, III, and IV were clearly distinguishable from those of section I except forB. Macrocarpa, which showed high similarity to wild species of section II. In a second experiment, 108 single-copy RFLP probes from sugar beet were Southern hybridized withB. procumbens DNA. A surprisingly low degree of homology (34%) was found. The results are discussed with regard to the taxonomic classification of the genusBeta.
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  • 8
    ISSN: 1617-4623
    Keywords: High-resolution mapping ; Karyotype evolution ; Restriction fragment length polymorphism (RFLP) ; Zycopersicon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several bacteriophage lambda clones containinginterstitialtelomererepeats (ITR) were isolated from a library of tomato genomic DNA by plaque hybridization with the clonedArabidopsis thaliana telomere repeat. Restriction fragments lacking highly repetitive DNA were identified and used as probes to map 14 of the 20 lambda clones. All of these markers mapped near the centromere on eight of the twelve tomato chromosomes. The exact centromere location of chromosomes 7 and 9 has recently been determined, and all ITR clones that localize to these two chromosomes map to the marker clusters known to contain the centromere. High-resolution mapping of one of these markers showed cosegregation of the telomere repeat with the marker cluster closest to the centromere in over 9000 meiotic products. We propose that the map location of interstitial telomere clones may reflect specific sequence interchanges between telomeric and centromeric regions and may provide an expedient means of localizing centromere positions.
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