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  • Articles  (18)
  • evolution
  • Springer  (18)
  • American Chemical Society
  • 1995-1999  (18)
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (18)
  • 1
    Electronic Resource
    Electronic Resource
    Phylogeny of Vicia Subgenus Vicia (Fabaceae) Based on Analysis of RAPDs and RFLP of PCR-Amplified Chloroplast Genes (1999)
    Springer
    Genetic resources and crop evolution 46 (1999), S. 149-161 
    Details
    ISSN: 1573-5109
    Keywords: evolution ; genetic resources ; PCR-RFLP ; RAPDs ; Vicia ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We report the results of two methods of DNA analysis to elucidate phylogenetic relationships among 29 Vicia subgen. Vicia species in comparison with two species of subgenus Vicilla sect. Vicilla. The methods employed were RAPD analysis of total genomic DNA and PCR-RFLP analysis of five chloroplast genes, rbcL, rpoB, 16S, psaA and trnK. The results of each method were similar and complementary, and support the current taxonomic systems of subsp. Vicia. According to RAPD and PCR-RFLP analysis the Narbonensis complex can be considered a well separated section, which may be related to section Vicia. Sections Vicia, Atossa and Wiggersia are separate, but closely related sections. Species of the section Hypechusa form a single monophyletic section, where V. lutea, V. anatolica and V. hyrcanica are quite remote from other species. Our results suggest that within the subgenus Vicia, V. faba is more closely related to V. bithynica and that these two species are most closely related to section Peregrinae. We found that PCR-RFLP of cp DNA provided more precise information concerning relationships between Vicia sections than RAPD analysis. However, RAPD analysis was more informative concerning diversity of closely related Vicia taxa, such as the variable groups, section Narbonensis and V. sativa aggregate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008640322198
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  • 2
    Electronic Resource
    Electronic Resource
    Fruit component analysis of south Pacific coconut palm populations (1997)
    Springer
    Genetic resources and crop evolution 44 (1997), S. 327-335 
    Details
    ISSN: 1573-5109
    Keywords: Cocos nucifera ; diversity ; evolution ; germplasm ; genetic resources ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The south Pacific region contains a large genetic resource for the genetic improvement of coconut palms (Cocos nucifera L.). A study of the diversity in the species was made during 1992/3 using fruit component analysis on a representative sample from 29 distinct south Pacific populations in order to characterise the germplasm present in the region. A large diversity in fruit morphology was found that ranged from populations exhibiting wild-type characters in central Pacific to populations displaying domesticated characteristics in Rennell Island, the Sikaiana Islands, the Marquesas Islands, and in Papua New Guinea. Many populations exhibited fruit characteristics intermediate between the two, which were thought to have arisen due to introgressive hybridisation between the wild and domesticated populations. Continuous variation in fruit morphology was found in these populations, and cluster analysis arbitrarily divided the continuum into discrete groups which were consistent with geographic affinities. Groups were defined in Melanesia, Western Polynesia and Eastern Polynesia. The continuum displayed clinal variation from populations with small fruit and low husk content in the west to large fruit and more husk in the east of the region. The wild and domesticated populations were found in disjunct pockets throughout the area, and did not form part of the clines. Most populations consisted of a wide range of fruit morphology, from individuals expressing wild-type characters to those with domestic-type characters. The occurrence of both wild and domesticated populations within the clinal variation indicates that further exploration should be made to determine the presence of other potentially useful populations. While this activity is proceeding, collection and conservation can proceed using the classification already defined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008652618350
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  • 3
    Electronic Resource
    Electronic Resource
    Cytogenetic relationships between Avena insularis (2n=28) and both A. strigosa (2n=14) and A. murphyi (2n=28) (1999)
    Springer
    Genetic resources and crop evolution 46 (1999), S. 501-504 
    Details
    ISSN: 1573-5109
    Keywords: cytogenetics ; evolution ; interspecific hybrids ; oat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The newly discovered tetraploid oat Avena insularis was crossed with the diploid A. strigosa and the tetraploid A. murphyi. Considerably reduced chromosome association at meiosis and a low average number of chiasmata per cell of the A. strigosa × A. insularis hybrids indicated that the diploid A. strigosa did not participate in the creation of A. insularis. From A. murphyi, A. insularis differed by four chromosomal rearrangements and the hybrids between them were sterile. The tetraploids A. magna, A. murphyi and A. insularis share the two to four floret large diaspore, which is adapted to heavy alluvial soil. They all, however, diverge from one another by four chromosomal rearrangements. At this point it is not possible to determine whether they have diverged from a single tetraploid progenitor, or developed from different diploid species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008728316354
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  • 4
    Electronic Resource
    Electronic Resource
    Variation and phylogeny of the triploid cultivated potatoSolanum chaucha Juz. et Buk. based on RAPD and isozyme markers (1995)
    Springer
    Genetic resources and crop evolution 42 (1995), S. 373-386 
    Details
    ISSN: 1573-5109
    Keywords: evolution ; genetic distance ; isozymes ; RAM ; Solanum chaucha ; varietal classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ninety four accessions of the cultivated triploid potatoS. chaucha were analyzed and classified in genotypic groups using 9 isozyme loci and RAPD markers disclosed by 20 arbitrary 10-mer primers. Eight isozyme loci out of nine were polymorphic. A total of 22 allozymes were analyzed but none of them were specific for any genotypic group. About half (52%) of the 102 RAPD markers scored, were polymorphic, all of them showing polymorphism among groups and rarely within groups. Eighteen RAPD markers were specific for certain genotypes. The isozyme markers showed a certain amount of intra group variation which made classification less reliable than with RAPD markers. A total of 10 triploid genetic groups were discriminated using both techniques together. A single primer was found to be sufficient to distinguish all 10 groups. All varieties of a single group are considered to have been derived from the same cross and then clonally propagated, even though there is a high amount of morphological variation within a single genotypic group due probably to somatic mutations. RAPD markers have been shown to be more reliable in the classification of triploid potato varieties than other genetic markers like isozymes, proteins and morphological traits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02432142
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  • 5
    Electronic Resource
    Electronic Resource
    How much biodiversity is enough? (1999)
    Springer
    Agroforestry systems 45 (1999), S. 23-41 
    Details
    ISSN: 1572-9680
    Keywords: agriculture ; evolution ; functional mimicry ; natural ecosystems ; sustainability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper addresses the question of how much biodiversity is enough in the context of the concept of agriculture as a mimic of nature. Following an historical review of the likely origins of ecosystems I show that the currently accepted components of biodiversity, viz. genetic, species and ecosystem, and their functional expression, are relevant to agriculture. Examples of adequate biodiversity are given and it is concluded that what constitutes enough biodiversity in an agricultural system is dependent upon the goal in question and will be different depending on whether the aim is, for example, to increase yield stability or deal with salinity, ground water levels, soil erosion, leaching of nutrients or weed control. The point is made that ecosystems and their composition are contingent in nature so the history of events, their frequency and intensity all need to be considered when interpreting the natural biodiversity present and thus determining what is enough in particular circumstances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006203318425
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  • 6
    Electronic Resource
    Electronic Resource
    Variation and phylogeny of the ribosomal DNA unit types and 5 S DNA inPetunia Jussieu (1995)
    Springer
    Genetic resources and crop evolution 42 (1995), S. 311-325 
    Details
    ISSN: 1573-5109
    Keywords: evolution ; 5 S DNA ; Petunia ; ribosomal DNA RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seven wildPetunia species including 2n = 18 species (P. parviflora Jussieu,P. linearis Hook.) and those with 2n = 14 (P. parodii Steene,P. axillaris Lam.,P. integrifolia Hook.,P. inflata R.E. Fries,P. violacea Lindl.) and tenPetunia hybrida horticultural lines were compared for polymorphisms in rDNA genes using the four restriction enzymesEcoRI,BamHI,HindIII andXhoI. All the unit types found in the lines pre-existed in the wild forms. There are two different sizes of either 11.45 or 11.6 kb./The 2n = 18 species are closely related to the 2n = 14 species, thus making thePetunia genus homogeneous. Moreover, it is likely thatP. hybrida lines originated in several kinds of crosses between these species. We constructed a dendrogram for all the 15 rDNA unit types found. Two main branches of the tree result from the presence or the absence ofHindIII sites. The main branch is divided according to variability at theEcoRI andBamHI sites. Taking into account the existence of several loci which carry one unit type only, we consider whether or not exchanges might occur between loci. Lines carrying two unit types and lines carrying three unit types support such a hypothesis.XhoI andBamHI fragments enable us to distinguish two types of 5S DNA corresponding to 2n = 18 and 2n = 14 species, respectively.P. hybrida lines and each 2n = 14 wild species carry one of the types only, that corresponds to one 5S DNA locus. The most parsimonious phylogenetic trees whatever the species chosen as the outgroup, do not fit with our knowledge ofPetunia and with taxonomy. This is likely because only few loci formed the basis of these phylogenetic constructions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02432135
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  • 7
    Electronic Resource
    Electronic Resource
    Arcelin in wild bean (Phaseolus vulgaris L.) seeds: sequence of arcelin 6 shows it is a member of the arcelins 1 and 2 subfamily (1998)
    Springer
    Genetic resources and crop evolution 45 (1998), S. 383-388 
    Details
    ISSN: 1573-5109
    Keywords: arcelin ; common bean ; evolution ; lectin-related genes ; lectin-related proteins ; Phaseolus genus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Arcelins are lectin-related proteins detected only in wild beans collected in Mexico and their presence has been related to resistance against the bean weevils. Six arcelin variants have been described and the gene sequence of four of them was determined. We have isolated and sequenced a cDNA clone encoding arcelin 6. Sequence data indicated that this protein is closely related to arcelin 1 and arcelin 2. The cluster dendrogram produced with the multiple alignment of the cDNA clones coding for arcelins showed that arcelins can be divided into three subgroups: i) arcelin 1, arcelin 2 and arcelin 6, ii) arcelin 4 and iii) arcelin 5a and arcelin 5b. Biochemical data indicate that arcelin 3 belongs to the same subgroup of arcelin 4. Southern blot analysis of genomic DNA yielded similar restriction patterns among members of each subgroup, confirming the results obtained with the multiple alignment. Furthermore, the hybridisation patterns were specific for each arcelin variant. On the basis of these evidences, we suggest that the lectin locus could be a useful tool for understanding evolutionary relationships in common bean and in the genus Phaseolus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008682917192
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  • 8
    Electronic Resource
    Electronic Resource
    Genetic variation vis-à-vis molecular polymorphism in groundnut, Arachis hypogaea L. (1998)
    Springer
    Genetic resources and crop evolution 45 (1998), S. 119-126 
    Details
    ISSN: 1573-5109
    Keywords: Arachis hypogaea ; DNA markers ; molecular polymorphism ; variation ; origin ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Recent studies on the genus Arachis using molecular markers have revealed very little demonstrable polymorphism in the cultivated groundnut, A. hypogaea. This has led to the hasty generalization that the groundnut lacks genetic variation. However, this is in complete contradiction to the results of other lines of investigations into the origin and evolution of A. hypogaea. Further, a characterization of the world collection for various traits also shows significant levels of variation for almost all genetic traits. The literature review in this article suggests that the lack of genetic variation was inferred because of an inadequacy in the material studied, and the range of techniques used to study molecular polymorphism. A comprehensive and rigorous examination of the material available in the groundnut world collection, either by improving current techniques, or by using such advanced techniques as SSRs and AFLP could well reveal polymorphism at the molecular level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008646422730
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  • 9
    Electronic Resource
    Electronic Resource
    A new species of Avena from Sicily, possibly the tetraploid progenitor of hexaploid oats (1998)
    Springer
    Genetic resources and crop evolution 45 (1998), S. 263-269 
    Details
    ISSN: 1573-5109
    Keywords: evolution ; interspecific hybridization ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A new species of oat, Avena insularis, is described. It was collected in southern Sicily where four populations were found on uncultivated clay soil. Morphologically, it is similar to the hexaploid wild oat A. sterilis, but can be distinguished by its smaller and more condensed panicle, less V-shaped dispersal unit and oblong disarticulation scar. Hybrids between A. insularis and the hexaploid cultivated oat A. sativa were obtained only when the latter was the seed parent in crosses. Chromosome pairing of the hybrids at meiosis was irregular with univalents and multivalents, but the mean number of chiasmata per cell was close to that of A. insularis. Furthermore, the hybrids were partially self-fertile. Thus, the newly discovered species seems closer to the hexaploid oats than any other tetraploid species, and is probably the tetraploid progenitor of hexaploid oats. Hybrids between A. insularis and A. magna were sterile because of irregular chromosome pairing at meiosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008657530466
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  • 10
    Electronic Resource
    Electronic Resource
    Evolution and improvement of cultivated amaranths with reference to genome relationship among A. cruentus, A. powellii and A. retroflexus (1999)
    Springer
    Genetic resources and crop evolution 46 (1999), S. 219-224 
    Details
    ISSN: 1573-5109
    Keywords: Amaranthus ; evolution ; genome relationship ; structural chromosome changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Meiotic studies were carried out in four accessions of three grain species, viz. Amaranthus cruentus, A. powellii and A. retroflexus and their F1 hybrids to elucidate the genome relationships between the cultivated and wild types and the cytogenetical mechanisms involved in speciation. All the three species were morphologically distinct and cytologically uniform with 17 bivalents at metaphase I. Morphologically the interspecific hybrids were either intermediate or had an overall dominance of wild parents. Chromosome analysis at meiotic metaphase I in the F1 interspecific hybrids of A. powellii with the Indian and Mexican accessions of A. cruentus showed an average of chromosome association of 1.0 IV + 0.10 III + 14.78 II + 0.14 I and 1.0 IV + 0.45 III + 14.20 II + 0.25 I and 5.81% in the former and 8.44% in the later pollen grain fertility, respectively and that of A. retroflexus with A. cruentus (Indian and Mexican) showed almost similar chromosomal associations. These studies show close genomic homology amongst all these three species involving certain chromosomal aberrations resulting in their evolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008664611893
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  • 11
    Electronic Resource
    Electronic Resource
    Chloroplast DNA diversity in brinjal eggplant (Solanum melongena L.) and related species (1997)
    Springer
    Euphytica 97 (1997), S. 295-301 
    Details
    ISSN: 1573-5060
    Keywords: chloroplast DNA ; brinjal eggplant ; Solanum incanum ; Solanum melongena ; Solanum aethiopicum ; systematics ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Chloroplast DNA (cpDNA) samples of brinjal eggplant (S. melongena) and representative related species including S. incanum sensu lato (or S. campylacanthum sensu stricto), S. lichtensteinii, S. marginatum, S. macrocarpon, S. anguivi and S. aethiopicum and also S. nigrum as an outgroup taxon, were digested by 14 restriction enzymes and analyzed by using electrophoresis and a cpDNA probe. All the species used here were clearly separated in the cpDNA analysis, except the pair S. anguivi and S. aethiopicum. From the dendrogram constructed by the unweighted pair-group method, it is suggested that S. incanum is the closest to S. melongena and the next closest species is S. macrocarpon followed by S. aethiopicum (and S. anguivi), S. lichtensteinii, S. marginatum and finally the outgroup taxon S. nigrum. The tree derived by the neighbour-joining method suggests phyletic relationships that agree with those indicated by crossability and seed coat anatomy, but conflict with conventional classifications based on morphology. In particular, members of sections Oliganthes and Melongena are not separated and no cpDNA variation was found within either of the morphologically diverse cultigens, S. aethiopicum and S. melongena. Paradoxically, the morphologically similar species S. incanum, S. lichtensteinii and S. marginatum have diverged greatly in their cpDNA. The significance of these results is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003000612441
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  • 12
    Electronic Resource
    Electronic Resource
    The impact of molecular systematics on hypotheses for the evolution of root nodule symbioses and implications for expanding symbioses to new host plant genera (1997)
    Springer
    Plant and soil 194 (1997), S. 185-192 
    Details
    ISSN: 1573-5036
    Keywords: actinorhizal plants ; evolution ; nitrogen fixation ; phylogenetic hypotheses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Current taxonomic schemes place plants that can participate in root nodule symbioses among disparate groups of angiosperms. According to the classification scheme of Cronquist (1981) which is based primarily on the analysis of morphological characters, host plants of rhizobial symbionts are placed in subclasses Rosidae and Hamamelidae, and those of Frankia are distributed among subclasses Rosidae, Hamamelidae, Magnoliidae and Dilleniidae. This broad phylogenetic distribution of nodulated plants has engendered the notion that nitrogen fixing endosymbionts, particularly those of actinorhizal plants, can interact with a very broad range of unrelated host plant genotypes. New angiosperm phylogenies based on DNA sequence comparisons reveal a markedly different relationship among nodulated plants and indicate that they form a more coherent group than has previously been thought (Chase et al., 1993; Swensen et al., 1994; Soltis et al., 1995). Molecular data support a single origin of the predisposition for root nodule symbiosis (Soltis et al., 1995) and at the same time support the occurrence of multiple origins of symbiosis within this group (Doyle, 1994; Swensen, 1996; Swensen and Mullin, In Press).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004240004063
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  • 13
    Electronic Resource
    Electronic Resource
    Biological nitrogen fixation in non-leguminous field crops: Facilitating the evolution of an effective association between Azospirillum and wheat (1997)
    Springer
    Plant and soil 194 (1997), S. 65-79 
    Details
    ISSN: 1573-5036
    Keywords: Azospirillum brasilense ; evolution ; nifA-lacZ ; nifH-lacZ ; nitrogen fixation ; para-nodules ; symbiosis ; wheat ; 2 ; 4-D
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Recent advances towards achieving significant nitrogen fixation by diazotrophs in symbioses with cereals are reviewed, referring to the literature on the evolution of effective symbioses involving rhizobia and Frankia as microsymbionts. Data indicating that strains of Acetobacter and Herbaspirillum colonizing specific cultivars of sugarcane as endophytes make a significant contribution to the nitrogen economy of this crop improves the prospects that similar associative systems may be developed for other gramineous species such as rice and wheat. By contrast, the transfer of nodulation genes similar to those in legumes or Parasponia to achieve nodulation in crops like rice and wheat is considered to be a more ambitious and distant goal. Progress in developing an effective associative system for cereals has been materially assisted by the development of genetic tools based on the application of lacZ and gusA fusions with the promoters of genes associated with nitrogen fixation. These reporter genes have provided clear evidence that ‘crack-entry’ at the points of emergence of lateral roots or of 2,4-D induced para-nodules is the most significant route of endophytic colonization. Furthermore, using the laboratory model of para-nodulated wheat, there is now evidence that the ability of azospirilla and other nitrogen fixing bacteria to colonize extensively as endophytes can be genetically controlled. The most successful strain of Azospirillum brasilense (Sp7-S) for endophytic colonization and nitrogen fixation in wheat seedlings is a mutant with reduced exopolysaccharide production. Most other strains of azospirilla do not colonize as endophytes and it is concluded that though these are poorly adapted to providing nitrogen for the host plant, they are well adapted for survival and persistence in soil. A research program combining the study of endophytic colonization by azospirilla with an examination of the factors controlling the effectiveness of association (oxygen tolerance and nitrogen transfer) is now being pursued. It is proposed that a process of facilitated evolution of para-nodulated wheat involving the stepwise genetic improvement of both the prospective microsymbionts and the cereal host will eventually lead to effective nitrogen-fixing associations. In the attempt to achieve this goal, continued study of the endophytes occurring naturally in sugar cane and other grasses (e.g. Azoarcus sp.) should be of assistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004260222528
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  • 14
    Electronic Resource
    Electronic Resource
    The Maturity Index, the evolution of nematode life history traits, adaptive radiation and cp-scaling (1999)
    Springer
    Plant and soil 212 (1999), S. 13-22 
    Details
    ISSN: 1573-5036
    Keywords: biomonitoring ; cp-scaling ; life history ; maturity index ; nematode ; evolution ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nematodes are increasingly being used in environmental studies. One of the potential parameters to measure the impact of disturbances and to monitor changes in structure and functioning of the below-ground ecosystem is the nematode Maturity Index; an index based on the proportion of colonizers (r-strategists s.l.) and persisters (K-strategists s.l.) in samples. In this paper the original allocation of nematode taxa on the colonizer-persister scale, and the tolerance and sensitivity of colonizers and persisters are discussed from an evolutionary viewpoint. The phenomenon that neither relative egg size nor body length is an unequivocal character to scale nematodes suggests that the main selection for life history traits occurred independently in the major evolutionary branches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004571900425
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  • 15
    Electronic Resource
    Electronic Resource
    Discovery of 2n gametes in tetraploid oat Avena vaviloviana (1995)
    Springer
    Euphytica 81 (1995), S. 1-6 
    Details
    ISSN: 1573-5060
    Keywords: Avena ; 2n gametes ; binucleate cell ; evolution ; sexual polyploidization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sexual polyploidization via the action of 2n gametes (gametes with the sporophytic chromosome number) has been identified as the most important evolutionary mode of polyploidization among plant genera. This study was conducted to determine whether 2n gametes are present in the tetraploid level of the genus Avena (2n=4×=28) Twenty tetraploid Avena lines, representing four species and one interspecific hybrid, were screened for pollen grain size in order to differentiate between n and 2n pollen. Avena vaviloviana (Malz.) Mordv. line PI 412767 was observed to contain large pollen grains at a 1.0% frequency. Cytogenetic analyses of pollen mother cells of PI 412767 revealed cells with double the normal chromosome number (i.e., 56 chromosomes at metaphase I and anaphase I). The mode of chromosome doubling was found to be failure of cell wall formation during the last mitotic division that preceded meiosis. The resulting binucleate cells underwent normal meiotic divisions and formed pollen grains with 28 chromosomes. Based on the formation and function of 2n gametes, three models involving diploid and tetraploid oat lines are proposed to describe possible evolutionary pathways for hexaploid oats. If stable synthetic hexaploid oat lines could be developed by utilizing 2n gametes from diploid and tetraploid oat species through bilateral sexual polyploidization, the resulting hexaploids could be used in breeding programs for transferring genes from diploids and tetraploids to cultivated hexaploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00022452
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  • 16
    Electronic Resource
    Electronic Resource
    Fish species – how and why (1999)
    Springer
    Reviews in fish biology and fisheries 9 (1999), S. 325-352 
    Details
    ISSN: 1573-5184
    Keywords: evolution ; nomenclature ; phylogeny ; species ; systematics ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract It is argued, with selected examples from freshwaterfish systematics, that species should be viewed as anexpression of self-perpetuated clustered variation innature, conforming to the phylogenetic speciesconcept. The importance of species lies in thefunctional and structural significance of theirdiagnostic characters. Species can be nested by theircharacters into a tree diagram (phylogeny) orhierarchical alignment structure (classification) ofcharacter distribution, which may be taken to reflectevolution, the unifying theory of organismaldiversification. The phylogenetic species concept,which emphasizes recognition of a pattern ofvariation, describes better than any other proposedconcept the units called species by systematists.Other concepts are based on processes and normally donot permit recognition of particular taxa. Specieshave unique histories, and speciation may proceed bydifferent mechanisms. Whereas it may be postulatedthat speciation entails an irreversible change in thegenetic structure of taxa, recognized by phenotypicexpression and apparently also maintained to a largeextent by selection for a particular phenotype,species recognition must remain independent ofassumptions about species history and spatialdistribution. Species are monophyletic taxa and thespecies category does not differ significantly inphylogenetic regard from other systematic categories.Species as such are not necessarily evolutionaryunits. It is recommended to apply species names withreference to the diagnostic characters of the speciesand to abandon the type specimen described by theInternational Code of Zoological Nomenclature as anomenclatural reference unit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008959313491
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  • 17
    Electronic Resource
    Electronic Resource
    Molecular and morphological characterization of monosomic additions in Beta vulgaris, carrying extra chromosomes of B. procumbens or B. patellaris (1997)
    Springer
    Molecular breeding 3 (1997), S. 147-157 
    Details
    ISSN: 1572-9788
    Keywords: Beta vulgaris ; Beta patellaris ; Beta procumbens ; section Procumbentes ; monosomic additions ; DNA fingerprinting ; repetitive probe ; morphological characteristics ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract DNA fingerprinting with three repetitive DNA sequences (OPX2, PB6-4 and Sat-121) was carried out on a set of 10 monosomic additions of Beta procumbens and 75 anonymous B. patellaris-derived monosomic additions in B. vulgaris, for characterization of the alien chromosomes at the DNA level. The probes are Procumbentes-specific and distributed over all chromosomes. Morphological characteristics were also used for the classification of B. patellaris monosomic addition families and for comparison with the morphology of the addition families of B. procumbens. DNA fingerprinting revealed unique patterns for almost all individual addition chromosomes of B. procumbens. However, it was concluded that chromosomes 1 and 6 of B. procumbens may be identical with the only difference that the chromosome referred to as 6 carries a susceptible allele for beet cyst nematode (BCN) resistance. In contrast, it was concluded that the two addition types with chromosome 2 are carrying different chromosomes of B. procumbens, so that one of them was renumbered to become the new chromosome 6. DNA fingerprinting of 75 anonymous B. patellaris-derived monosomic additions facilitated the identification and characterization of the alien chromosomes and the grouping of these additions into nine different groups. Several of these groups could be divided in two sub-groups on the basis of small differences in banding patterns. The results of the DNA fingerprinting led to the conclusion that B. patellaris most likely is an allotetraploid. It was also deduced that the BCN gene(s) in this species are homozygous and located on chromosome 1, while the pair of homoeologous chromosomes does not carry such BCN gene(s). Because of the allotetraploid nature of B. patellaris, preferential association occurs between the two homologous chromosomes containing the allele(s) for BCN resistance. Each group of B. patellaris addition families united by DNA fingerprinting had comparable morphological characteristics. Some of these morphological traits appeared to be chromosome-specific and were very useful for primary classification of the addition families. However, the present study showed that these morphological traits are not adequate for the identification of all alien chromosomes without the aid of additional markers. Because of similarities observed between molecular characteristics or the effects on plant morphology of several chromosomes of B. procumbens and B. patellaris it was concluded that B. procumbens could have been involved in the evolutionary history of B. patellaris.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009693619852
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  • 18
    Electronic Resource
    Electronic Resource
    Genetic correlations in resistance to morpholine and piperidine fungicides inPyrenophora teres populations (1995)
    Springer
    European journal of plant pathology 101 (1995), S. 93-99 
    Details
    ISSN: 1573-8469
    Keywords: fungicide resistance ; evolution ; quantitative genetics ; cross resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Highly significant genetic variation (P〈0.001) in resistance to the morpholine fungicides fenpropimorph, tridemorph and dodemorph and the piperidine fungicide, fenpropidin was found in different populations ofPyrenophore teres in North America and Europe which had not been previously exposed to these fungicides. Resistance phenotypes were continuously distributed for each fungicide in each population. Cross resistance relationships were determined by estimating genetic correlation coefficients in resistance to all pairwise combinations of fungicides. The majority of the correlation coefficients were highly positive for all fungicide combinations in all populations; eight of 36 (22%) coefficients were not significantly different from 1 (P〉0.05). This result is consistent with the hypothesis that many of the same genes, or genes in gametic disequilibrium, control resistance to more than one fungicide in most populations ofP. teres and that these fungicides comprise a single cross resistance group. Three of 36 (8%) correlation coefficients were not significantly different from 0 (P〉0.05) indicating that, in these populations, independent genes controlled resistance to these fungicides. The results of this study indicate that although most of the same genes control resistance to morpholine and piperidine fungicides inP. teres, differences in frequencies of these genes among populations can result in different cross resistance relationships from one population to another.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01876097
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