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  • 1990-1994  (13)
  • 1
    ISSN: 1432-2242
    Keywords: Potato ; Dihaploid ; Parthenogenesis ; Fertilization ; Chromosome elimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seventeen potato dihaploids, produced by pollinating the tetraploid (2n = 48) cv ‘Pentland Crown’ with pollen from Solanum phureja (2n = 24) dihaploid inducer clones, were studied. Since dihaploids are thought to develop parthenogenetically from unfertilized ovules they were expected to be euploid (2n = 24), but somatic chromosome counts showed that 15 of the 17 dihaploids were aneusomatic. Ten of the clones were predominantly diploid (2n = 24) with a proportion of hyperploid cells that contained 25 or 26 chromosomes. Five of the dihaploids contained variable numbers of triploid cells (2n = 36). RFLP analysis was used to determine whether the additional chromosomes were from S. phureja or S. tuberosum. Unique hybridizing fragments present in S. phureja but not in ‘Pentland Crown’ were identified. These S. phureja-specific restriction fragments were present in some of the dihaploid offspring of ‘Pentland Crown’. Of the 5 clones that contained triploid cells 4 had S. phureja type banding. Four of the 10 aneusomatic clones that contained hyperploid cells had the unique S. phureja hybridizing fragments. We propose that ovules of ‘Pentland Crown’ were fertilized by pollen from S. phureja and that the aneusomatic clones were derived from triploid zygotes from which some of the S. phureja chromosomes were eliminated. We consider that this is an additional mechanism of dihaploid formation in potato.
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  • 2
    ISSN: 1432-2242
    Keywords: Cocoa ; RAPDs ; DNA ; Polymorphism ; Genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Randomly amplified polymorphic DNA (RAPD) markers have been used to characterise cocoa clones representing the three main cultivated subpopulations: Criollo, Forastero and Trinitario. The use of single primers of arbitrary nucleotide sequence resulted in the selective amplification of DNA fragments which were unique to the individual cocoa clones studied. The use of a single primer allowed each of the clones evaluated to be unequivocally characterised. The application of RAPD markers for the evaluation of germplasm and cocoa improvement programmes are discussed.
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  • 3
    ISSN: 1432-2242
    Keywords: Hordeum ; Grain ; Isozymes ; Ribosomal DNA ; Genetic adaptation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Grain isozyme and ribosomal DNA (rDNA) variability was examined in Hordeum spontaneum populations sampled from 27 geographical sites in Israel. Considerable phenotypic variability was observed with variants of ADH1, EST3, EST10, BMY1 and WSP detected, which are not available in the H. vulgare gene pool. Seven new rDNA phenotypes were detected in the H. spontaneum populations. Shannon's index of diversity was used to partition the total phenotypic variation into between and within population components. Most of the variation occurred between H. spontaneum populations. The distribution of both grain isozyme and rDNA phenotypes was non-random and correlated with a range of ecogeographical factors. In particular, the G phenotype of BMY1 was restricted to the Negev Desert and Dead Sea regions of Israel. Over 78% of the variation in the frequency of this particular phenotype could be explained by the number of rainy days per year and mean temperature in January. This suggests that variation at this locus or at loci linked to it may be of adaptive significance and of value in the introgression of genes controlling abiotic stress tolerance from H. spontaneum into the H. vulgare gene pool.
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  • 4
    ISSN: 1432-2242
    Keywords: Vicia faba ; RFLPs ; Taxonomy ; mtDNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The taxonomic relationships between 52 accessions of 12 Vicia species and three accessions of Lathyrus were examined using nuclear RFLP- and PCR-generated data. Two hundred and sixty informative restriction fragments or amplification products were analysed by single linkage analysis, average cluster analysis, and the Wagner parsimony method. Dendrograms constructed from each type of analysis showed similar overall topologies and could be divided into three parts corresponding respectively to the Lathyrus outgroup, the species grouped in the section Faba/narbonemis complex, and the species belonging to the sections Hypechusa and Peregrinae. With few exceptions, the majority of accessions belonging to one species grouped together before branching to other species. An analysis of mitochondrial DNA phenotypes was both consistent with and complemented the results from the nuclear data. Overall, the species relationships show a good correlation with the classification of Maxted et al. but suggest that V. faba is more closely aligned to species from the sections Hypechusa and Peregrinae than to those in the narbonensis complex. In addition, the position of two new species, V. kalakhensis and V. eristaloides, as members of the narbonensis complex was supported by the molecular data, which also allowed a preliminary classification for recently collected Vicia accessions.
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  • 5
    ISSN: 1432-2242
    Keywords: Coffee ; Diversity ; RAPDs ; Gene introgression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract RAPD (randomly amplified polymorphic DNA) markers generated by arbitary decamers have been successfully employed to detect genetic polymorphisms between coffee species and between Coffea arabica genotypes. The RAPD profiles were used to construct dendrograms and these were consistent with the known history and evolution of Coffea arabica. Material originating from Ethiopia and the arabica sub-groups — C. arabica var. typica and C. arabica var. bourbon — were clearly distinguished. RAPD analysis therefore reflects morphological differences between the sub-groups and the geographical origin of the coffee material. Species-specific amplification products were also identified, but, more importantly, amplification products specific to C. canephora were identified in two C. arabica genotypes, Rume Sudan and Catimor 5175. This diagnostic product is therefore indicative of interspecific gene flow in coffee and has biological implications for selective introgressive hybridisation in coffee. Our study demonstrates the power of the polymerase chain reaction technology for the generation of genetic markers for long-lived perennial tree and bush crops.
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  • 6
    ISSN: 1432-2242
    Keywords: Doubled haploids ; Microspore ; Isozymes ; RFLPs ; Barley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Biochemical, molecular and morphological markers have been used to monitor the segregation of alleles at major gene loci in microspore-derived lines of four spring barley crosses and their parents. Significant deviations from the expected Mendelian ratios were observed for four of the ten markers studied in the cross. Distorted ratios were associated with loci located on chromosomes 4H and 6H. The differential transmission of alleles was in favour of the responsive parent (Blenheim) used in the anther culture studies. For the α-Amy-1 locus on chromosome 6H, the preferential transmission of Blenheim alleles was most pronounced in the haploid regenerants that were colchicine treated. These results are discussed in relation to the genetic control of androgenetic response in barley and with respect to the exploitation of another culture in barley improvement.
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  • 7
    ISSN: 1432-2242
    Keywords: RAPDs ; DHs ; Bulked segregant analysis ; QTLs ; Barley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Doubled haploid (DH) populations of barley have been used in combination with PCR-based polymorphic-assay procedures to identify molecular markers linked to genes controlling the milling energy requirement of the grain. Milling energy (ME) is a quantitative trait and locating individual quantitative trait loci (QTLs) involved the construction of bulks by combining DNA from DH families representing the extreme members of the distribution for ME. In addition, the individuals had alternative alleles at theRrn2 locus that has previously been shown to be linked to an ME QTL. The DNA bulks were screened with Randomly Amplified Polymorphic DNA (RAPD) markers and polymorphic amplification products tested for linkage to genes influencing the expression of ME in a DH population. Several markers were identified which are linked to a QTL controlling ME and the recombination fraction determined by maximum likelihood procedures. The results indicate that DHs in combination with RAPDs and bulked segregant analysis provide an efficient method for locating QTLs in barely. Furthermore, this approach is applicable to mapping other QTLs in a range of organisms from which DH or recombinant inbred lines can be extracted.
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  • 8
    ISSN: 1432-2242
    Keywords: RAPDs ; Mahoganies ; Genetic variation ; Conservation ; Genetic Improvement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Despite the economic importance of mahoganies (Meliaceae) little is known of the pattern of genetic variation within this family of tropical trees. We describe the application of a polymerase chain reaction (PCR)-based polymorphic DNA assay procedure random amplified polymorphic DNAs (RAPDs) to assess the extent of genetic variation between eight mahogany species from four genera. Pronounced genetic differentiation was found between the species and genera. There was a clear separation of Cedrela odorata from the other species, with 95% of the variable amplification products differing, whereas Lovoa trichilioides, Khaya spp. and Swietenia spp. were more closely grouped. These results are consistent with the current taxonomic viewpoint. A number of markers were found to be diagnostic for particular species, which could be of value in determining the status of putative hybrids. The application of RAPDs to the study of genetic variation in mahoganies is discussed in the context of developing genetic conservation and improvement strategies for these species.
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  • 9
    ISSN: 1615-6110
    Keywords: Angiosperms ; Rosaceae ; Rubus ; Chloroplast DNA ; restriction fragment length polymorphism ; cladistic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The variability in chloroplast DNA type of 20Rubus genotypes was examined by Southern hybridization. DNA extracted from theRubus accessions was digested with two restriction enzymes (EcoRI and EcoRV) and heterologous chloroplast DNA sequences from barley and pea were used as probes to detectRubus chloroplast DNA sequences on Southern blots ofRubus total DNA. Restriction fragment length polymorphism was detected and a total of 92 restriction fragments were generated by the probe/enzyme combinations examined. Cladistic principles based on the parsimony assumption were used to assemble a phylogenetic tree based on chloroplast restriction fragment length data. The phylogenetic tree grouped the taxonomically defined species and is in general agreement with information based on morphological criteria. However, the Japanese red raspberryR. illecebrosus was shown to have diverged considerably in terms of evolutionary time from other species in subg.Idaeobatus. Furthermore, the molecular approach provides a quantitative estimate of the relationship between species that is difficult to obtain from morphological data. In order to complement the chloroplast DNA information a ribosomal DNA probe was also included in the analysis and provided further information on the phylogenetic relationships withinRubus.
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  • 10
    ISSN: 1432-203X
    Keywords: Somatic hybrids ; Potato ; Reducing sugar ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A somatic hybridisation programme was undertaken to evaluate the expression of reducing sugar accumulation in potato. Interspecific hybrids created between the Solanum tuberosum cultivar Record and the diploid species Solanum phureja were evaluated at the morphological and molecular levels. These analyses indicated that the protoplast regenerants were partial (asymmetric) hybrids which had undergone elimination of S. phureja chromosomes. Tubers of the parents exhibited significant differences for reducing sugar accumulation during cold storage with S. phureja having lower levels of glucose and fructose than Record. The somatic hybrids resembled the S. phureja parent in terms of reducing sugar accumulation demonstrating that low reducing sugar accumulation is dominant to high reducing sugar accumulation in these particular genotypes. These results are discussed in relation to the exploitation of asymmetric hybridisation for the production of potato genotypes for the potato processing industry.
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