The allopolyploid origin of kiwifruit,Actinidia deliciosa (Actinidiaceae)

The genetic origin of kiwifruit (Actinidia deliciosa var.deliciosa) was studied using phylogenetic analysis of DNA sequences derived from the polygalacturonase gene. Results indicate that hexaploid kiwifruit had an allopolyploid origin with the diploidA. chinensis contributing one genome (genome A) and another (as yet unidentified) diploid species contributing a second genome (genome B). The results leave open the question of whether a third, distinct species contributed to the hexaploid kiwifruit genome. A tetraploid race ofA. chinensis is also suggested to be allopolyploid containing genomes A and B.     

Phylogenetic relationships and genetic diversity among members of theFestuca-Lolium complex (Poaceae) based on ITS sequence data

There have been few DNA sequencebased studies of phylogenetic relationships within theFestuca-Lolium complex. Here we infer the phylogeny of 31Festuca-Lolium taxa with a dataset of 116 ITS sequences. The results are consistent with previous studies that resolved two majorFestuca clades: one clade of fine fescues and another clade that containsLolium and associatedFestuca species. This study is unique in suggesting a third, basalFestuca clade, but support for the basal position of this group is low. Extensive sampling permitted investigation of the effects of lineage sorting and reticulate events on the evolution of the complex. Roughly half of the taxa show evidence of lineage sorting or reticulation, and the monophyly ofLolium has likely been obscured by reticulate events. Overall, polyploid species harbor higher levels of ITS sequence diversity than diploids; ITS sequence variants may provide clues to the identity of allopolyploid parents.     

Patterns of genetic differentiation in two annual bromegrasses,Bromus lanceolatus andB. hordeaceus (Poaceae)

Infraspecific genetic differentiation was analysed in two tetraploid annual bromegrasses,Bromus lanceolatus (from N Africa) andB. hordeaceus (from N Africa and France). Genetic analysis of populations was based on allozyme polymorphisms at 17 loci. Different fixed heterozygous phenotypes were scored in both species, according to their allopolyploid origin. In N Africa, more variation occurred among populations ofB. lanceolatus than ofB. hordeaceus. The variation was not randomly distributed among populations of both species. InB. lanceolatus, differentiation was correlated with climatic variables rather than with geographic distance between populations. Higher correlation of genetic differentiation with geographic distance occurred inB. hordeaceus, particularly at large geographic scale, between French and N African populations. Within each region, the populations appeared weakly genetically differentiated, even when belonging to different subspecies.     

Relationships between three species ofFestuca sect.Bovinae (Poaceae)

Seed protein electrophoresis confirms the existence of polymorphism among hexaploid populations ofFestuca arundinacea. Both protein and morphological results suggest thatF. pratensis andF. arundinacea should retain independent specific status. High protein homology of these two species withF. gigantea points towards phylogenetic links between these taxa.     

Phylogenetic and evolutionary implications of nuclear ribosomal DNA variation in dwarf dandelions (Krigia,Lactuceae, Asteraceae)

Restriction site and length variations of nrDNA were examined for 51 populations of seven species ofKrigia. The nrDNA repeat ranged in size from 8.7 to 9.6 kilobase (kb). The transcribed region, including the two ITSs, was 5.35 kb long in all examinedKrigia populations. In contrast, the size of the nontranscribed IGS varied from 3.35 to 4.25 kb. Eight different types of length-variations were identified among the 51 populations, including distinct nrDNA lengths in the tetraploid and diploid populations of bothK. biflora andK. virginica. However, a few variations were detected among populations of the same species or within a cytotype. All populations ofKrigia sect.Cymbia share a 600 bp insertion in IGS near the 18 S gene, and this feature suggests monophyly of the section. AllKrigia spp. had a conjugated type of subrepeat composed of approximately 75 basepairs (bp) and 125 bp. Base modifications in the gene coding regions were highly conserved among species. Forty-five restriction sites from 15 enzymes were mapped, 24 of which were variable among populations. Only four of the variable sites occurred in the rRNA coding region while 20 variable sites were detected in the noncoding regions. Collectively, 25 enzymes generated about 66 restriction sites in each nrDNA; this amounts to about 4.3% of the nrDNA repeat. A total of 50 restriction sites was variable, 28 of which were phylogenetically informative. Phylogenetic analyses of site mutations indicated that two sections ofKrigia, sect.Cymbia and sect.Krigia, are monophyletic. In addition, relationships among several species were congruent with other sources of data, such as cpDNA restriction site variation and morphology. Both length and restriction site variation supported an allopolyploid origin of the hexaploidK. montana. The average sequence divergence value inKrigia nrDNA was 40 times greater than that of the chloroplast DNA. The rapid evolution of nrDNA sequences was primarily due to changes of the IGS sequences.     

Detecting Nucleotide Additivity from Direct Sequences is a SNAP: An Example from Sidalcea (Malvaceae)

Abstract: Superimposed nucleotide additivity patterns (SNAPs) were detected from direct sequences of the nuclear ribosomal DNA internal transcribed spacers in a complex of perennial Sidalcea species (Malvaceae) from the Pacific Northwest of the United States. Although only 2.8 % sequence variation exists among the eight ITS accessions, parsimony analysis identified two distinct lineages within this complex consistent with known ploidy levels. Six SNAPs were identified in a known tetraploid S. virgata, suggesting allopolyploid origins from diploid S. virgata and one of two hexaploid Sidalcea species. A dosage effect detected at all six SNAP sites is consistent with the unequal sized parental genomes of allopolyploid S. virgata.     

The use of a non-coding region of chloroplast DNA in phylogenetic studies of the subtribeSonchinae (Asteraceae:Lactuceae)

The systematic utility of sequences from a non-coding region of chloroplast DNA (cpDNA) betweenpsbA andtrnH^(GUG) was examined by assessing phylogenetic relationships in subtribeSonchinae (Asteraceae:Lactuceae). Primers constructed against highly conserved regions of tRNA genes were used for PCR amplification and sequencing. ThepsbA-trnH intergenic spacer contains several insertions and deletions (indels) inSonchinae with the length varying from 385 to 450 bp. Sequence divergence ranges from 0.00% to 7.54% withinSonchinae, with an average of 2.4%. Average sequence divergence inSonchus subg.Sonchus is 2.0%, while the mean for subg.Dendrosonchus and its close relatives in Macaronesia (the woodySonchus alliance) is 1.0%. Our results suggest that this region does not evolve rapidly enough to resolve relationships among closely related genera or insular endemics in theAsteraceae. The phylogenetic utility ofpsbA-trnH sequences of the non-coding cpDNA was compared to sequences from the ITS region of nuclear ribosomal DNA. The results suggest that ITS sequences evolve nearly four times faster thanpsbA-trnH intergenic spacer sequences. Furthermore, the ITS sequences provide more variable and phylogenetically informative sites and generate more highly resolved trees with more strongly supported clades, and thus are more suitable for phylogenetic comparisons at lower taxonomic levels than thepsbA-trnH intergenic chloroplast sequences.     

Close sequence identity between ribosomal DNA episomes of the non-pathogenicEntamoeba dispar and pathogenicEntamoeba histolytica

Entamoeba dispar andEntamoeba histolytica are now recognized as two distinct species-the former being nonpathogenic to humans. We had earlier studied the organization of ribosomal RNA genes inE. histolytica. Here we report the analysis of ribosomal RNA genes inE. dispar. The rRNA genes ofE. dispar, like their counterpart inE. histolytica are located on a circular rDNA molecule. From restriction map analysis, the size ofE. dispar rDNA circle was estimated to be 24·4 kb. The size was also confirmed by linearizing the circle withBsaHI, and by limited DNAseI digestion. The restriction map of theE. dispar rDNA circle showed close similarity to EhR1, the rDNA circle ofE. histolytica strain HM-1:IMSS which has two rDNA units per circle. The various families of short tandem repeats found in the upstream and downstream intergenic spacers (IGS) of EhR1 were also present inE. dispar. Partial sequencing of the cloned fragments ofE. dispar rDNA and comparison with EhR1 revealed only 2·6% to 3·8% sequence divergence in the IGS. The region Tr and the adjoiningPvuI repeats in the IGS of EhR1, which are missing in thoseE. histolytica strains that have one rDNA unit per circle, were present in theE. dispar rDNA circle. Such close similarity in the overall organization and sequence of the IGS of rDNAs of two different species is uncommon. In fact the spacer sequences were only slightly more divergent than the 18S rRNA gene sequence which differs by 1·6% in the two species. The most divergent sequence betweenE. histolytica andE. dispar was the internal transcribed spacer, ITS2. Therefore, it was concluded that probes derived from the ITS1 and ITS 2 sequences would be more reliable and reproducible than probes from the IGS regions used earlier for identifying these species.     

Cytotaxonomic study of genusHymenasplenium (Aspleniaceae) in Xishuangbanna, Southwestern China

The gametic chromosome numbers of sevenHymenasplenium (Aspleniaceae) species from Xishuangbanna, Yunnan Prov., China, were investigated. All the examined individuals ofH. obscurum, H. cheilosorum andH. latipinnum were sexual diploids with n=39 chromosomes. Intraspecific cytological variation was found inH. excisum, which has a sexual diploid (n=39) and a tetraploid (n=78). Only a triploid apogamous cytotype (n=ca.117) was found inH. laterepens. Hymenasplenium apogamum showed the most complicated intraspecific variation and included a sexual diploid (n=39), a sexual tetraploid (n=78) and an apogamous triploid (n=ca.117). This work reports for the first time the sexual diploids ofH. cheilosorum andH. apogamum, which are only apogamous elsewhere in east Asia, Himalayas and Indochina. These results may indicate that this area is one of the diversity centers ofHymenasplenium. Most of the above species have chromosome numbers based on x=39. In contrast,H. costarisorum contains a sexual diploid (n=36) and a sexual tetraploid (n=72), indicating that its basic number is x=36.     

Polyploidy and aneuploidy inOphrys,Orchis, andAnacamptis (Orchidaceae)

Studies on chromosome numbers and karyotypes in Orchid taxa from Apulia (Italy) revealed triploid complements inOphrys tenthredinifera andOrchis italica. InO. tenthredinifera there is no significant difference between the diploid and the triploid karyotypes. The tetraploid cytotype ofAnacamptis pyramidalis forms 36 bivalents during metaphase I in embryo sac mother cells. Aneuploidy was noticed inOphrys bertolonii ×O. tarentina with chromosome numbers n = 19 and 2n = 38. There were diploid (2n = 2x = 36), tetraploid (2n = 4x = 72), hexaploid (2n = 6x = 108) and octoploid (2n = 8x = 144) cells in the ovary wall of the diploid hybridOphrys apulica ×O. bombyliflora. Evolutionary trends inOphrys andOrchis chromosomes are discussed.     

Biosystematic studies on the genusIsoetes (Isoetaceae) in Japan. III. Variability within qualitative and quantitative morphology of spores

Qualitative and quantitative characteristics of mega- and microspores from all the cytotypes of JapaneseIsoetes are described based on the voucher specimens whose chromosome numbers were known. InI. japonica, the hexaploid possessed reticulate megaspores and levigate microspores, while the octaploid and the heptaploid had echinate microspores. Mega- and microspores of the hexaploid and the octaploid were of normal appearance, while those of the heptaploid displayed polymorphism. The tetraploid and the hexaploid ofI. sinensis resembled each other, since they both possessed cristate megaspores and echinate microspores. Echinate megaspores and levigate microspores characterized the diploidI. asiatica. The spore size was largely variable within each cytotype, while the size of the megaspores varied more than that of the microspores. The microspore length was closely correlated with polyploid level. InI. sinensis, the mean microspore length of the tetraploid was 27.6 μm while that of the hexaploid was 31.9 μm, hence these two cytotypes were easily distinguishable. In the hexaploidI. japonica, variations in mega-and microspore size displayed geoclinal variation showing a positive correlation (r=0.43–0.55) with the longitude and the latitude of the populations. A palynological key for cytotypes is presented.     

The annual species ofAdonis (Ranunculaceae)—a polyploid complex

The five annual species ofAdonis L., sect.Adonis, growing in Israel, form a series of diploid, tetraploid and hexaploid species. Their somatic chromosome numbers are 2n = 16 inA. annua L.,A. dentata Del. andA. palaestina Boiss., 2n = 32 inA. microcarpa DC., 2n = 48 inA. aestivalis L.; counts forA. dentata, A. palaestina andA. microcarpa are new records. There are indications that alloploidization may have been involved in the process of speciation in sect.Adonis. A taxonomic survey of the 8 species of the section reveals that a higher ploidy level is usually combined with a larger distribution area.     

Cytogenetics and cytotaxonomy ofVelloziaceae

Chromosome number and other cytological features are reported from 35 species ofVelloziaceae, including several African and Brazilian populations. All analyzed species show areticulate interphase nuclei and prophase/prometaphase chromosomes with proximal early condensation. Most heteropycnotic blocks do not seem to correspond to heterochromatin since, at least inVellozia patens, they do not stain differentially after C-banding procedures. Regarding the chromosome number, three main groups could be identified. The first comprised diploid species of the generaNanuza, Vellozia and the Brazilian species ofXerophyta with 2n = 14 or 16; the second comprised tetraploid species with 2n = 34, and included all Brazilian species of subfam.Barbacenioideae; the third group, of hexaploid species, comprised the African representatives of the genusXerophyta. A single population ofVellozia, possibly of hybrid origin, had 2n 32. A basic number of x = 8 is proposed for the family. The karyological information supports the hypothesis that theVelloziaceae originated on the South American, rather than on the African continent.     

Chloroplastrps16 intron phylogeny of the tribeSileneae (Caryophyllaceae)

Intron sequences of the chloroplast generps16 from 46 species were used to examine phylogenetic relationships indicated by nrDNA ITS sequence variation in the tribeSileneae (Caryophyllaceae, Caryophylloideae). This region has previously not been utilized for phylogenetic purposes but the results presented here suggest that it is a consistent and valuable complement to the ITS sequences. Therps16 intron trees are largely congruent with the ITS trees. All the major hypotheses suggested by the ITS data are supported, often at similar bootstrap levels. The joint usage ofrps16 intron and ITS sequences provides a powerful tool for resolving many of the difficult taxonomic issues in the tribeSileneae. Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday     

Cytotaxonomy and breeding system of the genusBiscutella (Cruciferae)

Chromosome counts were determined for 46 populations ofBiscutella representing 28 taxa. The genus was found to contain diploid taxa with 2n = 12, 16 and 18, tetraploid taxa with 2n = 36 and hexaploid taxa having 2n = 54.B. laevigata L. s. l. consists of diploid and tetraploid populations which are poorly differentiated morphologically. TetraploidB. laevigata s. l. and hexaploidB. variegata Boiss. & Reuter (s. l.) are characterized by chromosomal instability. The variation in chromosome numbers and the occurrence of polyploidy is discussed in relation to the taxonomy of the genus. An investigation of the breeding system showed that most of the annual species were self-compatible and partly inbreeding and most of the perennial species self-incompatible and, therefore, outbreeding, while one annual species,B. cichoriifolia Loisel., showed both systems.     

A genome-specific repeat sequence from kiwifruit (Actinidia deliciosa var. deliciosa)

Summary Six members of a family of moderately repetitive DNA sequences from kiwifruit (Actinidia deliciosa var. deliciosa) have been cloned and characterized. The repeat family is composed of elements that have a unit length of 463 bp, are highly methylated, occur in tandem arrays of at least 50 kb in length, and constitute about 0.5% of the kiwifruit genome. Individual elements diverge in nucleotide sequence by up to 5%, which suggests that the repeat sequence is evolving rapidly. Homologous sequences were found in A. deliciosa var. chlorocarpa. The repeat sequence was not found under low stringency hybridization conditions in the diploid A. chinensis, the species most closely related to the hexaploid kiwifruit, or in eight other Actinidia species. However, homologous repeats were detected in a tetraploid species, A. chrysantha. The results provide the first molecular evidence to suggest that kiwifruit may be an allopolyploid species.     

Repeated DNA sequences inTriticum (Poaceae): Chromosomal mapping and its bearing on the evolution of B and G genomes

The somatic chromosomes ofTriticum turgicum var.durum cv. Langdon andT. dicoccoides (AABB tetraploids),T. timopheevii, andT. araraticum (AAGG tetraploids) were assayed for distribution patterns of a highly repeated 120bp DNA sequence by in situ hybridization. The repeated sequence appears to be an ancient sequence shared withSecale andAegilops. The distribution patterns of the chromosomes were compared to the patterns of the A and B genome chromosomes ofT. aestivum cv. Chinese Spring (AABBDD hexaploid).T. turgidum andT. dicoccoides were observed to have identical in situ hybridization patterns. In both species, nine chromosomes with a total of 21 sites of hybridization were observed. The pattern, with few exceptions, was identical to that of Chinese Spring.T. araraticum andT. timopheevii were observed to have different patterns. InT. araraticum, six chromosomes with 21 total hybridization sites are present while inT. timopheevii nine chromosomes with 19 total sites exist. Major differences in hybridization patterns were observed between the B and G genomes. The divergence of the tetraploid wheats in this study appears to have resulted in changes in location, not in amount, of the ancient repeated sequence.     

New or rare data on chromosome numbers in several taxa of the genus<Emphasis Type="Italic">Artemisia (Asteraceae)</Emphasis> in Poland

Chromosome counts in 16 populations of fiveArtemisia species from Poland are presented in this paper. Those ofA. annua (2n=18) andA. dracunculus (2n=90) are reported for the first time in Polish populations. The decaploid level (2n=90) is described for the first time in non-cultivated populations ofA. dracunculus, and several cases of aneusomaty (intraindividual aneuploid variations in chromosome number: 2n=87, 88 and 89) have been detected in this species. In addition to the already known diploid number (2n=18), the tetraploid level (2n=36) has been detected inA. absinthium. The same two numbers have been recorded inA. abrotanum, which represents the first tetraploid count in populations of this taxon occurring outside botanical gardens. Finally, the chromosome number ofArtemisia campestris subsp.sericea (tetraploid, 2n=36) is reported for the first time. The relevance of polyploidy for the evolution of the genus and other cytotaxonomic or cytobiogeographical aspects are briefly discussed.     

Molecular analysis of the D-genome of the Triticeae

Summary The chromosome of three tetraploid Aegilops L. species containing the D-genome were analyzed by in situ hybridization with a repeated DNA sequence clone pAS1 isolated from Aegilops squarrosa and observed to be D-genome specific. This sequence is found on all seven D-genome chromosome pairs of A. squarrosa and hexaploid wheat. Two distinct D-genome patterns were observed in the tetraploid species. The D-genome of A. cylindrica was similar to hexaploid wheat. Seven pairs of chromosomes having large amounts and numerous sites of the sequence were observed. Five chromosome pairs with fewer and smaller sites of the repetitive sequence were observed in the D-genomes of A. crassa and A. ventricosa. In addition to these major repeated sequence differences, chromosomal modifications appear to have occurred between T. aestivum and A. cylindrica and between A. crassa and A. ventricosa resulting in changes with respect to location of the sequence between the respective species. D-genome divergence with respect to pAS1 sequence appears to have occurred at least in two forms, one characterized by the changes in amount of repetitive sequence and the second by changes in location of the sequence.     

Evolution of parental ITS regions of nuclear rDNA in allopolyploid Aegilops (Poaceae) species

The genus Aegilops comprises approximately 25 diploid, tetraploid and hexaploid species, in which the genome types of all allopolyploids involve either U or D genome, or both of them. The internal transcribed spacer (ITS) region of 18S-26S nuclear ribosomal DNA (rDNA) from 11 allopolyploid species and 7 related diploid species in the genus were directly sequenced by pooled PCR products. Phylogenetic analyses for tracing evolutionary patterns of parental rDNA in allopolyploid species were performed using the neighbor-joining method. The D genome involved tree included three clades (CC-DDCC, DDMM-DDMMSS-DDMMUU, and MM-MhMh-DDNN), but did not include Ae. squarrosa (DD). It indicated that the rDNA of ancestral D genome had been somewhat differentiated in allopolyploids. The U genome involved tree showed that the allopolyploids and their common ancestor, Ae. umbellulata, formed a clade, suggesting that rDNA in UUMM and UUSS genomes has been homogenizing toward that of ancestral U genome. The phylogenetic pattern of U genome based on ITS sequences also supported the "pivotal-differential" hypothesis.