TheTy1-copia group retrotransposons inVicia species: copy number, sequence heterogeneity and chromosomal localisation

We present an in-depth study of theTy1-copia group of retrotransposons within the plant genusVicia, which contains species with widely differing genome sizes. We have compared the numbers and sequence heterogeneities of these genetic elements in three diploidVicia species chosen to represent large (V. faba, 1C=13.3 pg), medium (V. melanops, 1C=11.5 pg) and small (V. sativa, 1C=2.3 pg) genomes within the genus. The copy numbers of the retrotransposons are all high but vary greatly, withV. faba containing approximately 10⁶ copies,V. melanops about 1000 copies andV. sativa 5000 copies. The degree of sequence heterogeneity ofTy1-copia group elements correlates with their copy number within each genome, but neither heterogeneity nor copy number are related to the genome size of the host. In situ hybridization to metaphase chromosomes shows that the retrotransposons inV. faba are distributed throughout all chromosomes but are much less abundant in certain heterochromatic regions. These results are discussed in the context of plant retrotransposon evolution.     

Étude cytotaxinomique de quelquesDipsacaceae d'Iran

Chromosome numbers for 28 Iranian populations ofDipsacaceae, corresponding to 14 taxa, are presented. New are those forScabiosa aff.olivieri var.pinnatisecta, S. persica, Pterocephalus canus, P. kurdicus, Dipsacus strigosus, Cephalaria dichaetophora, C. hirsuta, C. microcephala, C. subindivisa andC. aff.sublanata. Except forC. syriaca (x = 5) andC. dichaetophora (x = 7 : new basic chromosome number forCephalaria), all species examined are characterized by the basic chromosome number (x = 9). Instances of aneusomaty, B-chromosomes, aneuploidy, dysploidy, and polyploidy have also been found.

     

Genome size and base composition of five<Emphasis Type="Italic"> Pinus</Emphasis> species from the Balkan region

The 2C DNA content and base composition of five Pinus (2n=24) species and two Pinus subspecies from the Balkan region have been estimated by flow cytometry. P. heldreichii (five populations) and P. peuce (one population) were assessed for the first time, as also were subspecies of P. nigra (three populations—two of subspecies nigra and one of subspecies dalmatica) along with P. sylvestris, and P. mugo from the same region. The 2C DNA values of these Pinus ranged from 42.5 pg to 54.9 pg (41.7–53.8×10⁹ bp), and the base composition was quite stable (about 39.5% GC). Significant differences were observed between two subspecies of P. nigra and even between two populations of subsp. nigra. The two other species (P. sylvestris and P. mugo) had 2C values of 42.5 pg and 42.8 pg, respectively, while that of P. peuce was 54.9 pg. These genome sizes are in accordance with published values except for P. sylvestris, which was 20% below estimates made by other authors.Communicated by M. Beckert     

Genome size and polyploidy variation in the tropical hardwood genusTerminalia (Combretaceae)

Chromosome complements and 2C DNA amounts of six species ofTerminalia have been studied.Terminalia oliveri, T. myriocarpa andT. arjuna are diploid (2n = 24),T. chebula andT. bellirica are tetraploid (2n = 48),T. muelleri shows a triploid number (2n = 36). Two well demarcated groups of species are recognizable on the basis of chromosome length and 2C DNA values which range from 3.60 pg (T. oliveri) to 12.80 pg (T. bellirica) showing a 3.5-fold difference. Differences of DNA per basic genome or per chromosome are greatest (1.97-fold) betweenT. oliveri andT. arjuna. Two species groups (1)T. oliveri andT. chebula, and (2)T. myriocarpa, T. arjuna, T. muelleri, T. bellirica, therefore are well differentiated by DNA per basic genome, irrespective of polyploidy. The mean values of the two groups are 1.81 pg and 3.34 pg, respectively, showing a 1.84-fold difference. Within diploids and tetraploids there is 1.97-fold and 1.76-fold variation, respectively.     

TheTy1-copia group retrotransposons inVicia species: copy number,sequence heterogeneity and chromosomal localisation

We present an in-depth study of theTy1-copia group of retrotransposons within the plant genusVicia, which contains species with widely differing genome sizes. We have compared the numbers and sequence heterogeneities of these genetic elements in three diploidVicia species chosen to represent large (V. faba, 1C=13.3 pg), medium (V. melanops, 1C=11.5 pg) and small (V. sativa, 1C=2.3 pg) genomes within the genus. The copy numbers of the retrotransposons are all high but vary greatly, withV. faba containing approximately 10⁶ copies,V. melanops about 1000 copies andV. sativa 5000 copies. The degree of sequence heterogeneity ofTy1-copia group elements correlates with their copy number within each genome, but neither heterogeneity nor copy number are related to the genome size of the host. In situ hybridization to metaphase chromosomes shows that the retrotransposons inV. faba are distributed throughout all chromosomes but are much less abundant in certain heterochromatic regions. These results are discussed in the context of plant retrotransposon evolution.     

A new pollen type,C-banded and fluorochrome counterstained chromosomes,and evolution inGuatteria and related genera (Annonaceae)

Guatteria, Guatteriopsis, Guatteriella andHeteropetalum share the same conspicuous pollen type which is new for theSpermatophyta. It is zonoaperturate with a folded aperture region and an extremely reduced exine. First chromosome counts and karyotype analyses forGuatteriopsis (4 species investigated) andGuatteriella (1 species) are identical with those ofGuatteria (19 species seen): 2n = 28. The genome is characterized by diploidization and partly telocentric chromosomes. Sequentially Giemsa C- and fluorochrome banded chromosomes and interphase nuclei are described. The cuticular folding pattern is distinct forHeteropetalum only. Growth forms and ecology are reported for many species. The evolutionary pattern of theGuatteria group is discussed and compared with other genera and families.     

Assessment of random amplified polymorphic DNA (RAPD) for determining the origin ofYoungia koidzumiana Kitamura (compositae)

We determined the parental species ofYoungia koidzumiana (a natural interspecific hybrid) using PCR and arbitrary 10-mer primers to generate random amplified polymorphic DNA (RAPD) markers. These markers, generated by three primers, were sufficient to distinguishYoungia sonchifolia, Youngia denticulata, Youngia chelidoniifolia, andY. koidzumiana. The electrophoresis profiles of the amplified products from each of the four species were then compared. Three primers produced a total of 42 scorable markers; nine were specific markers forY. denticulata andY. chelidoni-ifolia. The length of the amplified DNA fragments ranged from 370 to 2500 b p. The three primers revealed polymorphic bands, which were indicators of the parental species ofY. koidzumiana. These bands showed a combination of specific profiles forY. denticulata andY. chelidoniifolia. Our results also were comparable to the data obtained for flowering times, floret numbers, and chromosome numbers of the four species. Therefore, we suggest thatY. koidzumiana is a hybrid betweenY. denticulata andY. chelidoniifolia}, and that RAPD markers are well suited for assessing the origins of plant species.     

Genome Size Determination in Peronosporales (Oomycota) by Feulgen Image Analysis

Genome size was determined, by nuclear Feulgen staining and image analysis, in 46 accessions of 31 species of Peronosporales (Oomycota), including important plant pathogens such asBremia lactucae, Plasmopara viticola, Pseudoperonospora cubensis,andPseudoperonospora humuli.The 1C DNA contents ranged from 0.046 (45.6 Mb) to 0.163 pg (159.9 Mb). This is 0.041- to 0.144-fold that ofGlycine max(soybean, 1C = 1.134 pg), which was used as an internal standard for genome size determination. The linearity of Feulgen absorbance photometry method over this range was demonstrated by calibration ofAspergillusspecies (1C = 31–38 Mb) againstGlycine,which revealed differences of less than 6% compared to the published CHEF data. The low coefficients of variation (usually between 5 and 10%), repeatability of the results, and compatibility with CHEF data prove the resolution power of Feulgen image analysis. The applicability and limitations of Feulgen photometry are discussed in relation to other methods of genome size determination (CHEF gel electrophoresis, reassociation kinetics, genomic reconstruction) that have been previously applied to Oomycota.     

Chromosome banding and genome size differentiation inProspero (Hyacinthaceae): Diploids

Prospero is a Mediterranean autumn-flowering genus ofHyacinthaceae commonly classified inScilla asS. autumnalis andS. obtusifolia. Extensive dysploid and polyploid variation has been reported. In the present study 77 diploid accessions from the western to the eastern part of the area of distribution, the major part being from continental Greece and Crete, have been analysed for karyotype structure and, in part, for genome size. Methods employed were acetocarmine staining, Giemsa C-banding, fluorochrome staining mainly with chromomycin A₃/DAPI, silver impregnation, and Feulgen densitometry. Banded idiograms were established with a computer assisted karyotype analysis procedure. Chromosome numbers were 2n = 8 inP. obtusifolium, and 2n = 12 and 14 inP. autumnale s. l. Dispensable euchromatic chromosome segments and different types of B chromosomes occurred. Among the cytotypes with 2n = 14 two karyotypes from Turkey differed from each other and from the rest in form, position of the nucleolar constriction, and in genome size. The remaining accessions were similar in karyotype shape but three levels of genome size could be discerned, the highest (1C = 7.50 pg) being found on the Iberian Peninsula, an intermediate one on Corsica and Malta, and the lowest (4.27 pg) in the Aegean. The karyotype with 2n = 12 had an intermediate genome size, and that ofP. obtusifolium a relatively low one. Heterochromatin amount was generally low, but some karyotypes showed characteristic banding patterns. The relationship between the chromosome complements with 2n = 14, 12 and 8 is discussed on the basis of idiograms and DNA amounts.The authors respectfully dedicate this papers to emer. o. Prof. Dr.Elisabeth Tschermak-Woess on the occasion of her 80th birthday.     

A karyomorphological study of the genusHypericum (Hypericaceae) in Japan

Chromosome numbers were determined in 226 collections ofHypericum of Japan, representing nine species and one interspecific hybrid. These included the first cytological records forH. erectum var.caespitosum, H. samaniense, H. hakonense, H. sikokumontanum, H. kamtschaticum var.kamtschaticum, H. kamtschaticum var.hondoense, H. pseudopetiolatum, H. yojiroanum andH. tosaense. Counts of 2n=16 were made throughout for collections of six species, and those of 2n=18 forH. ascyron. Intraspecific polyploidy was found inH. samaniense (2x and 3x, x=8) andH. pseudopetiolatum (2x and 4x, x=8). Results of the karyotype analysis showed that three different karyotypes could be recognized, and they were parallel to the subdivision ofHypericum by Kimura (1951). The chromosomes were very small and mostly median centromeric. It was suggested that the role of polyploidy in the evolutionary differentiation ofHypericum in Japan might have been rather limited.     

Karyological and taxonomical notes on three species of the genus<Emphasis Type="Italic">Epipactis (Neottioideae,Orchidaceae)</Emphasis> in the central-western Iberian Peninsula

Studies on the karyotypes and chromosome numbers of species ofEpipactis from the central-western Iberian Peninsula show that the species harbour enormous chromosome variability, have very asymmetric karyotypes and possess extraordinary diversity of aneuploidy. This paper provides the first report of a chromosome number forE. fageticola (2n=36, 40 + 0–2 B), as well as the first counts for Portuguese populations ofE. helleborine (2n=18, 32, 38) and first counts for Iberian populations ofE. tremolsii (n=20, 30, 2n=16, 24, 32, 34, 36, 38 + 1B, 40 + 1B, 52, 60). Among populations ofE. tremolsii there is a significant differentiation in ecology and somatic chromosome number, suggesting that there may be two different taxa in the region studied. Chromosomes are large to small, ranging in length from 10.8 μm to 1.8 μm. Karyotype asymmetry is of type 3C inE. fageticola andE. tremolsii and 2C inE. helleborine andE. tremolsii.     

Karyological studies onGentiana sect.Chondrophyllae (Gentianaceae) from China

Nineteen populations of fifteen species ofGentiana sect.Chondrophyllae from China were observed cytologically.Gentiana alsinoides, G. anisostemon, G. asterocalyx, G. exigua, G. heterostemon, G. intricata, G. praticola, G. pseudoaquatica, G. spathulifolia, andG. subintricata all had the same chromosome number of 2n = 20 (or n = 10), whereasG. piasezkii had 2n = 36,G. squarrosa 2n = 38,G. prattii 2n = 18,G. aristata 2n = 14 (n = 7), andG. heleonastes 2n = 12. All these chromosome numbers are documented here for the first time, except forG. squarrosa, where it is a new number report. The basic numbers of x = 6, x = 7 and x = 19 are new for the section. Karyotype analyses of some species revealed that, except for a few cases, the species examined mainly had metacentric chromosomes. 2n = 20 = 2m(SAT) + 18m was found to be the main type of karyotype for the species with 2n = 20. Chromosomal evolution and its mechanism in this section are also discussed.     

Karyology,nuclear genome quantification and characterization of the carrageenophytesEucheuma andKappaphycus (Gigartinales)

DNA reassociation kinetics were used to determine nuclear genome organization and complexity in the carrageenophyteKappaphycus alvarezii. Results indicate the presence of three second order components corresponding to fast (12%), intermediate (38%) and slow (50%) fractions. Microspectrophotometry with the DNA-localizing fluorochrome DAPI confirmed ploidy level differences in the gametophytic and tetrasporophytic phases. Comparison of mean nuclear DNA (I _f ) values to chicken erythrocytes (RBC) resulted in pg/2C genome estimates:Eucheuma denticulatum=0.35,E. isiforme=0.44,Kappaphycus alvarezii=0.32 andK. striatum=0.42. Karyological studies of tetraspore mother cells during diakinesis using aceto-orcein revealed a chromosome complement of 10 forEucheuma denticulatum andKappaphycus alvarezii.     

Conifer genome sizes of 172 species,covering 64 of 67 genera,range from 8 to 72 picogram

Nuclear genome size of conifers as measured by flow cytometry with propidium iodide was investigated, striving to collect at least a single species from each genus. 64 out of 67 genera and 172 species were measured. Of the 67 genera, 21 are reported here for the first time and the same is true for 76 species. This nearly doubles the number of measured genera and adds 50% to the number of analyzed species. Conifers have chromosome numbers in the range of n = (7)10–12(19). However, the nuclear DNA content (2C‐value) is shown here to range from 8.3 to 71.6 picogram. The largest genome contains roughly 6 × 10¹⁰ more base pairs than the smallest genome. Genome sizes are evaluated and compared with available taxonomic treatments. For the mainly (sub)tropical Podocarpaceae small genome sizes were found with a 2C‐value of only 8–28 pg, with 13.5 pg on average. For the Taxaceae 2C‐values from 23–60 pg were determined. Not surprisingly, the genus Pinus with 97 species (39 species measured here) has a broad range with 2C = 38–72 pg. A factor of 2 difference is also found in the Cupressaceae (136 species) with nuclear DNA contents in the range 18–35 pg. Apart from the allohexaploid Sequoia, ploidy plays a role only in Juniperus and some new polyploids are found. The data on genome size support conclusions on phylogenetic relationships obtained by DNA sequencing. Flow cytometry is applicable even to young plants or seeds for the monitoring of trade in endangered species.     

Isozyme evidence regarding the origins of three allopolyploid species ofPolytrichastrum (Polytrichaceae, Bryophyta)

Electrophoretic data show thatPolytrichastrum pallidisetum, P. ohioense, andP. sexangulare are allopolyploids. They display fixed, heterozygous banding patterns at five to six of the 11 enzyme loci that we screened. In total, we sampled 304 populations representing three genera (Polytrichastrum, Polytrichum, andPogonatum) and 18 species in our examination of the allopolyploids and their putative haploid progenitors. There were no extant species that fit perfectly as a progenitor of any allopolyploid. BothP. pallidisetum andP. ohioense appear to have originated as intergeneric hybrids between one progenitor with aPolytrichastrum-type genome and another with aPolytrichum-type genome. The extant haploid species with the most similar genomes to the putative progenitors ofP. pallidisetum werePolytrichastrum appalachianum andPolytrichum commune, whereas forPolytrichastrum ohioense the species werePolytrichastrum formosum (orP. longisetum) andPolytrichum commune. Polytrichastrum sexangulare was genetically more similar to species ofPogonatum, as was one taxon that appears to be one of its progenitors,P. sexangulare var.vulcanicum ( =Polytrichum/Pogonatum sphaerothecium). The other progenitor also must have possessed alleles that are common in species ofPogonatum. The Polytrichaceae are a relatively ancient group of mosses, and the hybridizations that gave rise to these allopolyploids may have occurred long ago. It is likely that the genomes of the original progenitors have changed over time or that those progenitors are now extinct.     

Chromosome numbers of European blackberries (Rubus subg.Rubus,Rosaceae)

Chromosome numbers are presented for 32 collections of 29 European blackberry species (Rubus subg.Rubus) from Germany. One species is triploid (2n = 21), 27 species are tetraploid, (2n = 28), and one species is pentaploid (2n = 35). Chromosome numbers are reported for the first time ofR. adspersus, R. amisiensis, R. calvus, R. conothyrsoides, R. contractipes, R. demissus, R. elegantispinosus, R. ferocior, R. foliosus, R. hypomalacus, R. leucandrus, R. nemorosus, R. platyacanthus, R. praecox, R. rhombifolius, andR. rhytidophyllus. Chromosome numbers forR. dasyphyllus, R. gelertii, R. glandithyrsos, R. lamprocaulos, R. lindebergii, R. macrophyllus, R. montanus, R. muenteri, R. pedemontanus, R. polyanthemus, R. senticosus, R. silvaticus, andR. vigorosus are confirmed.     

A survey of C-band patterns in chromosomes ofLilium (Liliaceae)

C-band patterns are described for 20Lilium spp. distributed across six sections. All species have a similar basic karyotype (n = 12) but C-bands differ markedly between them. The patterns are characterized by a dispersed scattering of thin intercalary bands as well as centric and NOR bands. Only one species,L. canadense, shows a clear equilocal pattern with intercalary C-bands occurring proximally in all of the longer chromosome arms. Comparing species, similar patterns are revealed forL. regale andL. sulphureum, forL. formosanum andL. longiflorum (all in sect.Leucolirion) and to a lesser extent forL. hansonii, L. martagon, andL. tsingtauense (sect.Martagon). The pattern forL. henryi (previously classed in sect.Sinomartagon) matches those ofL. regale andL. sulphureum quite well and its transfer to sect.Leucolirion is proposed. This is consistent with results from interspecies hybrids betweenL. henryi andL. regale (and related species) which are reportedly fertile. No other clear similarities in C-band patterns were seen across species. It seems that C-band patterns change rapidly inLilium and hence their usefulness in classification will be restricted to identifying closely related species.Dedicated to Prof.D. G. Catcheside on the 80th anniversary of his birth.     

Quantification and characterization of nuclear genomes in commercial red seaweeds (Gracilariales) from the Philippines

Eight species of Gracilariaceae from the Philippines, representing the generaGracilaria, Gracilariopsis andHydropuntia, were investigated to quantify and characterize their nuclear genomes. DNA reassociation kinetics were used to determine nuclear genome organization and complexity in six of these species. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repetitive sequences varied from 13–74% and unique DNA ranged from 26–84%. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to quantify nuclear DNA contents. Comparisons of mean nuclear DNA (I _f ) values to chicken erythrocytes (RBC) resulted in an estimate of 0.38–0.43 pg/2 C genomes for seven of the species investigated. Preliminary analyses of agar content and quality confirm the economic potential ofGracilaria firma, Gracilaria sp. 2 from Sorsogon andGracilariopsis bailinae. Nuclear genome profiles developed from data for genome size, organization and complexity are compared with data for agar quantity and quality. Gel quality and quantity do not appear to be correlated with either large repetitive fraction DNA or a high degree of genome complexity.Author for correspondence     

Cytology and systematics in JapaneseArisaema (Araceae)

Chromosome numbers are determined from 37 populations attributed to 22 taxa of JapaneseArisaema. Of them, chromosome numbers ofA. limbatum var.conspicuum (2n=26),A. minus (2n=26),A. nambae (2n=28) andA. seppikoense (2n=26) are determined for the first time. New chromosome numbers, 2n=26, are reported forA. aequinoctiale, A. limbatum, A. stenophyllum, A. undulatifolium andA. yoshinagae. Three modes of basic chromosome numbers,x=14,x=13 andx=12, occur in JapaneseArisaema. Precise karyotypic comparisons of 20 taxa reveal that taxa withx=14 andx=13 share 26 major chromosome arms and have an obvious chromosomal relationship. One of two submeta-centric chromosomes inx=13 corresponds to two telo-centric chromosomes inx=14. InA. ternatipartitum with 2n=6x=72, ten out of 12 basic chromosomes are the most similar in size and arm ratio with larger ten chromosomes ofA. ringens among JapaneseArisaema examined. A basic chromosome number ofx=14 is the commonest in the genusArisaema and the remaining basic chromosome numbers,x=13 andx=12, seem to be derived through dysploidal reduction by translocating large segments of major arm of telo-centric chromosome onto other minor arm of telo-centric followed by loss of the remainings including a centromere, and by loss of two telo-centrics fromx=14, respectively. Some systematic problems of JapaneseArisaema are discussed based on new cytological data.Arisaema hatizyoense, A. minus andA. nambae are accepted as independent species.