Cyanogenesis variation in the Turnera sidoides L. polyploid complex (Turneraceae)

This study constitutes the first investigation of cyanogenesis variation within the Turnera sidoides autopolyploid complex. The qualitative and quantitative analysis carried out in 38 populations showed that the five subspecies of the complex are cyanogenic, although the levels of cyanide released varied both between and within subspecies. Between the subspecies, carnea , holosericea and integrifolia showed higher values of HCN released than subspecies pinnatifida and sidoides . Within subspecies, there is a tendency toward an increment of mean cyanide values with ploidy levels and different hypotheses are considered in order to explain this variation. The study of cyanogenesis in populations from different geographical areas cultivated under uniform greenhouse conditions showed that, in the widespread subspecies pinnatifida , HCN variation may also reflect the action of different selection pressures, since populations having dissimilar cyanide levels grow in different phytogeographical provinces with different climatic regimes. On the other hand, the fact that the variation of HCN released was greater between populations from different geographical areas than that observed between diploid and tetraploid populations of the same area provides additional evidence for the multiple origins of polyploids of the T. sidoides complex.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 141 , 85–94.     

Genetic diversity among Korean bermudagrass (Cynodon spp.) ecotypes characterized by morphological, cytological and molecular approaches

The genus Cynodon comprises ten species. The objective of this study was to evaluate the genetic diversity of Korean bermudagrasses at the morphological, cytological and molecular levels. Morphological parameters, the nuclear DNA content and ploidy levels were observed in 43 bermudagrass ecotypes. AFLP markers were evaluated to define the genetic diversity, and chromosome counts were made to confirm the inferred cytotypes. Nuclear DNA contents were in the ranges 1.42-1.56, 1.94-2.19, 2.54, and 2.77-2.85 pg/2C for the triploid, tetraploid, pentaploid, and hexaploid accessions, respectively. The inferred cytotypes were triploid (2n = 3x = 27), tetraploid (2n = 4x = 36), pentaploid (2n = 5x = 45), and hexaploid (2n = 6x = 54), but the majority of the collections were tetraploid (81%). Mitotic chromosome counts verified the corresponding ploidy levels. The fast growing fine-textured ecotypes had lower ploidy levels, while the pentaploids and hexaploids were coarse types. The genetic similarity ranged from 0.42 to 0.94 with an average of 0.64. UPGMA cluster analysis and principle coordinate analysis separated the ecotypes into 6 distinct groups. The genetic similarity suggests natural hybridization between the different cytotypes, which could be useful resources for future breeding and genetic studies.     

Patterns of cytotype variation of <Emphasis Type="Italic">Turnera sidoides</Emphasis> subsp. <Emphasis Type="Italic">pinnatifida</Emphasis> (Turneraceae) in mountain ranges of central Argentina

Cytogeographical variability among 564 plants from 26 populations of Turnera sidoides subsp. pinnatifida in mountain ranges of central Argentina was analysed with meiotic chromosome counts and flow cytometry and is described at regional and local scales. Populations were primarily tetraploids (2n = 4x = 28), although diploid (2n = 2x = 14), hexaploid (2n = 2x = 42), and mixed populations of diploids and triploids (2n = 3x = 21) were also found. Diploids, triploids, and hexaploids were fewer in number and restricted to narrow areas, while tetraploids were the most common and geographically widespread cytotype. Diploids grew at higher altitudes and in colder and wet locations; tetraploids had the broadest ecological spectrum, while hexaploids occurred at the lowest altitudes and in drier conditions. The cytotypes were also spatially segregated at a microgeographical scale. Diploids grew in the piedmont, tetraploids were in the adjacent valley, and in the contact zone of both cytotypes, patches of diploids and triploids were found. At a regional scale, the distribution of the cytotypes may be governed by a combination of ecological and historical variables, while segregation in the contact zone may be independent of the selective environment because the cytotypes are unable to coexist as a result of reproductive exclusion. The role of triploids is also discussed.     

The origin and meiotic behaviour of hexaploid northern wheatgrass (Agropyron dasystachyum)

The occurrence of hexaploid (2n = 6x = 42) forms in some otherwise natural tetraploid populations of Agropyron dasystachyum (2n = 4x = 28) was cytologically detected and studied. The hexaploid plants are morphologically similar to the tetraploids except for a small reduction in the anther size. The general survey of chromosome numbers of natural Northern Wheatgrass (A. dasystachyum 2n = 4x = 28) populations derived from eight different regions of Alberta indicated that the occurrence of hexaploid variants was not restricted to a single locality. A comparative study of chromosome pairing in the natural and the synthetic hexaploids revealed that the naturally occurring 42-chromosomed plants of A. dasystachyum originated as a result of fertilization between unreduced (SSHH) and the natural (SH) gametes, both coming from the tetraploid form of A. dasystachyum. Based on chromosome pairing, the genomes of the natural hexaploid A. dasystachyum have been designated as SSSHHH. The natural hexaploids appear to intercross among themselves and also with tetraploids producing euploid and aneuploid hybrids. The possible evolutionary significance of these findings is briefly discussed.     

A new cytotype of Jacobaea vulgaris (Asteraceae): frequency,morphology and origin

Jacobaea vulgaris subsp. vulgaris (syn. Senecio jacobaea subsp. jacobaea) constitutes an intricate polyploid complex distributed in Europe. Four cytotypes have been reported in this species, three with euploid (diploid, tetraploid and octoploid; 2n=20, 40 and 80) and one with aneuploid (2n=32) chromosome numbers. Here we report that the diploid chromosome number (2n=20) reported from Bulgaria is due to misidentification with Jacobaea aquatica. On the other hand, we have discovered a new, hexaploid (2n=6x=60) cytotype within J. vulgaris subsp. vulgaris using flow cytometry. The new cytotype occurs within four sympatric populations of otherwise tetraploid and octoploid plants in Pannonia (one locality in the eastern Czech Republic and two localities in southwestern Slovakia) and in Podillya (one locality in western Ukraine). The frequency of hexaploid individuals within 76 studied populations is very low (only 10 of 693 analysed plants), and hexaploids probably represent hybrids between tetraploid and octoploid plants. Three mixed populations with hexaploid plants were subjected to detailed morphological and pollen fertility analyses. Multivariate morphometric analysis reveals partial separation of tetraploid and octoploid plants, whereas hexaploid individuals are similar in morphology to octoploids. In comparison with tetraploids, octoploids and hexaploids exhibit slightly longer ray florets, involucral bracts and tubular florets and more hairy outer achenes. Hexaploid plants display larger pollen grains and lower pollen fertility compared to tetraploids and octoploids.     

Phytogeographical studies ofCalamagrostis sachalinensis (Gramineae)

Chromosome numbers were determined on 223 collections ofCalamagrostis sachalinensis from 18 localities in Japan. The plants were found to be tetraploid (2n=28), hexaploid (2n=42) or octoploid (2n=56). A few collections were found to include one or two B-chromosomes. The tetraploid collections were made from central Honshu and Mt. Apoi in Hokkaido, while the hexaploids and the octoploids were detected in many localities. Pollen examination of these collections showed that the tetraploids with but one exception have good pollen and the hexaploids and the octoploids have no pollen or have bad pollen with stainability less than 10%. With the help of pollen examination of a number of herbarium specimens, the distribution of the tetraploids and that of the assemblage of the hexaploids and octoploids were delineated. Morphological studies indicated that the tetraploid, hexaploid and octoploid plants can not be separated in gross and spikelet morphology and that the tetraploids in central Honshu and those in Mt. Apoi are significantly different in leaf features. It was concluded thatC. sachalinensis represents an apo-amphimictic complex, which includes the following four races: 1) tetraploid, amphimictic, having thin leaf blades 5–10 mm broad and growing on the subalpine conifer forest belt and the conifer forest-alpine ecotone in the mountains of central Honshu; 2) tetraploid, amphimictic, having hard leaf blades 2–6 mm broad and growing on the stony, arid and exposed alpine belt on Mt. Apoi in Hokkaido; 3) hexaploid, mainly apomictic, the most variable ecologically, widely distributed; 4) octoploid, mainly apomictic, frequent in the upper montane to alpine belts, probably widely distributed.     

A cytotaxonomic study of theCalamagrostis purpurea —langsdorffii—canadensis complex in the lowlands of hokkaido

A chromosome survey of 278 individuals from 52 localities confirmed, that the principal components of theCalamagrostis purpurea—langsdorffi—canadensis complex in the lowlands of Hokkaido are tetraploid (2n=28) and octoploid (2n=56). A few hexploids (2n=42), were also found, but they may be either a triploid of the tetraploid plants or a hybrid between the tetraploid and octoploid plants. These hexaploids clearly differ in origin from the North American plants with 2n=42 which are generally placed underC. canadensis. The tetraploids and the octoploids are significantly different in pollen size but resemble each other in other morphological features and ecological requirements. These two races are also not disparate in distribution within Hokkaido. The tetraploids in Hokkaido are closely related to the tetraploids known in Alaska, and these tetraploid plants may be continuously distributed from Hokkaido to Alaska. The octoploids in Hokkaido have shown good pollen. They seem to have had a somewhat different course of evolution fromC. purpurea s. str. which principally reproduces in an apomictic manner.     

Calamagrostis hakonensis (Poaceae): Distribution and differentiation of cytotypes

Chromosome counts were made for a total of 540 collections ofCalamagrostis hakonensis from 66 localities ranging from Kyushu to Hokkaido. Distribution and habitat preferences of the cytotypes involved are described. Sympatric occurrence of tetraploids (=semidiploids, 2n=28) and higher polyploids, as well as that of septaploids and plants at hexaploid and/or octoploid levels, was confirmed in several localities, and mixtures of hexaploids and octoploids within a population were frequently observed. Plants at hexaploid and octoploid levels were the most abundant and widespread. An examination of pollen of the voucher specimens showed that tetraploids (amphimictic) had good pollen, while higher polyploids (apomictic) were generally devoid of pollen and very rarely produced moderately good pollen, the grains of higher polyploids being larger than those of tetraploids. Distributions of tetraploids and higher polyploids were more precisely delineated through an examination of pollen of many herbarium specimens. In relation to the processes by which the complicated internal structure ofC. hakonensis has been established, the following subjects are discussed: infraspecific hybridization between ecotypically differentiated populations, enrichment of variability through occasional sexual reproduction expected in plants with more than 2n=42, persistence of the variants by apomictic reproduction, and probable roles of some extinct taxa.     

Karyotype analysis and polyploidy in Palaua and a comparison with its sister group Fuertesimalva(Malvaceae)

Palaua(Malveae,Malvaceae)comprises 15 species endemic to the hyperarid coastal desert of Chile and Peru.So far,chromosome counts have been known for two diploid species(2n=2x=10)only.Here we report new chromosome numbers for 12 species of Palaua and four of its sister group Fuertesimalva.Karyotypes including 4,6-diamidino-2-phenylindole dihydrochloride(DAPI)/chromomycin(CMA3)fluorescent banding are presented for selected species representative of each of the main clades of Palaua.An important finding is the discovery of polyploids in one exclusively tetraploid species(P.trisepala)and four species with mixed diploid and tetraploid cytotypes(P.dissecta,P.mollendoensis,P.moschata,and P.tomentosa).The diploid and tetraploid karyotypes are all unimodal,symmetrical and show one or two pairs of satellite chromosomes with their associated CMA+/DAPI- band depending on the cytotype.For some of the tetraploids an autopolyploid origin is suggested.     

Variation and differentiation in Hordeum marinum (Poaceae)

In Hordeum marinum two subspecies are recognized, viz. ssp. marinum , 2x and ssp. gussoneanum , 2x and 4x. The tetraploid cytotype has a more eastern distribution in the Mediterranean area than the two diploids. Crosses and meiotic data in hybrids revealed that the three cytotypes are closely related. The tetraploid ssp. gussoneanum behaves like a true alloploid but evidently has a very strong diploidizing mechanism, which prevents recombination between the genomes. The isoenzyme pattern shows differences between the cytotypes and a clinal differentiation in ssp. marinum.     

Ecological differentiation,lack of hybrids involving diploids,and asymmetric gene flow between polyploids in narrow contact zones of Senecio carniolicus (syn. Jacobaea carniolica,Asteraceae)

Areas of immediate contact of different cytotypes offer a unique opportunity to study evolutionary dynamics within heteroploid species and to assess isolation mechanisms governing coexistence of cytotypes of different ploidy. The degree of reproductive isolation of cytotypes, that is, the frequency of heteroploid crosses and subsequent formation of viable and (partly) fertile hybrids, plays a crucial role for the long‐term integrity of lineages in contact zones. Here, we assessed fine‐scale distribution, spatial clustering, and ecological niches as well as patterns of gene flow in parental and hybrid cytotypes in zones of immediate contact of di‐, tetra‐, and hexaploid Senecio carniolicus (Asteraceae) in the Eastern Alps. Cytotypes were spatially separated also at the investigated microscale; the strongest spatial separation was observed for the fully interfertile tetra‐ and hexaploids. The three main cytotypes showed highly significant niche differences, which were, however, weaker than across their entire distribution ranges in the Eastern Alps. Individuals with intermediate ploidy levels were found neither in the diploid/tetraploid nor in the diploid/hexaploid contact zones indicating strong reproductive barriers. In contrast, pentaploid individuals were frequent in the tetraploid/hexaploid contact zone, albeit limited to a narrow strip in the immediate contact zone of their parental cytotypes. AFLP fingerprinting data revealed introgressive gene flow mediated by pentaploid hybrids from tetra‐ to hexaploid individuals, but not vice versa. The ecological niche of pentaploids differed significantly from that of tetraploids but not from hexaploids.     

Meiotic pairing as an indicator of genome composition in polyploid prairie cordgrass (<Emphasis Type="Italic">Spartina pectinata</Emphasis> Link)

The existence of neopolyploidy in prairie cordgrass (Spartina pectinata Link) has been documented. The neohexaploid was discovered coexisting with tetraploids in central Illinois, and has been reported to exhibit competitiveness in the natural environment. It is hypothesized that the natural tetraploid cytotype produced the hexaploid cytotype via production of unreduced gametes. Meiosis I chromosome pairing was observed in tetraploid (2n?=?4x?=?40), hexaploid (2n?=?6x?=?60), and octoploid (2n?=?8x?=?80) accessions and the percentage of meiotic abnormality was determined. Significant differences in meiotic abnormality exist between tetraploid, hexaploid, and octoploid cytotypes. An elevated incidence of abnormal, predominantly trivalent pairing in the neohexaploid suggests that it may possess homologous chromosomes in sets of three, in contrast to the tetraploid and octoploid cytotypes, which likely possess homologous chromosomes in sets of two. Abnormal chromosome pairing in the hexaploid may result in unequal allocation of chromosomes to daughter cells during later stages of meiosis. Chromosome pairing patterns in tetraploid, hexaploid, and octoploid cytotypes indicate genome compositions of AABB, AAABBB, and AABBA′A′B′B′, respectively.     

Occurrence of tetraploid and octoploid cytotypes in Senecio jacobaea ssp. jacobaea (Asteraceae) in Pannonia and the Carpathians

Four different cytotypes have been reported for Senecio jacobaea L. ssp. jacobaea throughout Europe, with the most common occurrence of tetraploids (2 n  = 40). Here we present a survey of previously published chromosome number data on this subspecies and its geographical distribution, and focus on populations from Pannonia and the Carpathians. Two ploidy levels have been determined in the study area, using chromosome counting and flow cytometry: tetraploid (2 n  = 40) and octoploid (2 n  = 80). Fifty-one populations originating from Slovakia, Austria, the Czech Republic, Hungary, Ukraine and Romania have been analysed. Multivariate morphometric analyses have been performed on 39 populations to study morphological differentiation between these two cytotypes. Despite slight morphological tendencies expressed on the level of populations, tetraploid and octoploids cannot be reliably distinguished morphologically and they are not taxonomically classified formally here.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153 , 231–242.     

中国西南六种广义拂子茅属(禾本科)植物的染色体数目

广义拂子茅属（Calamagrostis）是一个世界温带广布的大属,有些作者又分为拂子茅属和野青茅属,但近期的研究表明处理为一个属较为合适。中国共有37种广义拂子茅属植物,但至今没有任何染色体的研究。本文报道了其中产于中国西南6种野青茅的染色体数目,其中Deyeuxia petelotii 4个居群,D．diffusa,D．moupinemis,D．nivicola和D．flvens各一个居群都是四倍体（2n=4x=28）,D．neglecta为六倍体（2n=6x=42）。根据广义拂子茅属植物染色体倍性特征,该属植物中至今未发现二倍体,四倍体是该属中倍性最低和最普遍的,广义拂子茅属的演化很可能是在四倍体的水平上进行的。由于以上几个四倍体种均是狭域分布的类群,所以可能是由四倍体的祖先隔离分化形成的。     

拟鹅观草属3种植物的核型研究

对禾本科小麦族拟鹅观草属物种Pseudoroegneria geniculata、P.geniculata ssp.scythica和P.geniculata ssp.pruinifera的核型进行了研究.结果显示:P.geniculata和P.geniculata ssp.scythica为四倍体物种,P.geniculata ssp.pruinifera为六倍体物种;P.geniculata、P.geniculata ssp.scythica和P.geniculata ssp.pruinifera的核型公式分别为2n=4x=28=18m(2sat)+10sm(2sat)、2n=4x=28=28m(2sat)和2n=6x=42=36m(6sat)+6sm(2sat);P.geniculata和P.geniculata ssp.pruinifera为2A核型,而P.geniculata ssp.scythica为1A核型.研究表明:3种植物的核型存在差异;P.geniculata ssp.pruinifera的核型为首次报道,其核型明显不同于P.geniculata和P.geniculata ssp.scythica.     

中国西南六种广义拂子茅属( 禾本科) 植物的染色体数目

广义拂子茅属( Calamagrostis) 是一个世界温带广布的大属, 有些作者又分为拂子茅属和野青茅属, 但近期的研究表明处理为一个属较为合适。中国共有37 种广义拂子茅属植物, 但至今没有任何染色体的研究。本文报道了其中产于中国西南6 种野青茅的染色体数目, 其中Deyeuxia petelotii 4 个居群, D1 diffusa, D1 moupinensis, D1 nivicola 和D1f lavens 各一个居群都是四倍体( 2n= 4x= 28) , D1 neglecta 为六倍体( 2n= 6x= 42) 。根据广义拂子茅属植物染色体倍性特征, 该属植物中至今未发现二倍体, 四倍体是该属中倍性最低和最普遍的, 广义拂子茅属的演化很可能是在四倍体的水平上进行的。由于以上几个四倍体种均是狭域分布的类群, 所以可能是由四倍体的祖先隔离分化形成的。     

Sympatric occurrences of various cytotypes of Vaccinium sect. Oxycoccus (Ericaceae)

Flow cytometry was employed to estimate ploidy levels in Vaccinium sect. Oxycoccus. Twelve localities in the Czech Republic, Sweden and Denmark were studied in detail in order to investigate the potential sympatric growth of various cytotypes. Diploid V. microcarpum and tetraploid, pentaploid and hexaploid individuals of V. oxycoccos were found among the 296 accessions analyzed. Both species as well as various (up to all three) ploidy levels of V. oxycoccos co-occurred at the same locality. Mixed accessions (containing various cytotypes) were even ascertained on a very fine spatial scale (20 × 20 cm). Pentaploid plants of probable hybrid origin have been found in Sweden for the first time. The population growing on peat bog near Lyngby, Copenhagen (Denmark) consisted of both hexaploids and tetraploids. This site refers to the discovery of hexaploid cranberries in the late twentieths of the last century. The results represent further support for merging of all polyploid cytotypes (4x—6x) into a single taxon.     

Agrostis mertensii (Poaceae) in hokkaido

Populations of theAgrostis flaccida-mertensii complex in Hokkaido were examined as part of the taxonomic study of this complex, which has a wide range and comprises a polyploid series of 2x–8x (x=7). The principal aim was to clarify the taxonomic status of hexaploids growing in Hokkaido. Field explorations were made in the mountains and on the coasts in Hokkaido, and the materials were gathered from 19 localities. The occurrence of four cytotypes (2x, 4x, 6x, 8x), as well as some triploids and septaploids, of this complex in Hokkaido was confirmed, and the ranges of respective cytotypes were delineated. Morphological examinations showed that diploids, triploids and tetraploids are referable toAgrostis flaccida and octoploids toA. mertensii. The hexaploids of Hokkaido were morphologically different fromA. flaccida and also from the related hexaploid species,A. tateyamensis, distributed in Honshu. The hexaploids were quite similar to octoploidA. mertensii in all the morphological features examined and also in habitat preference. Septaploids were sterile hybrids between hexaploids and octoploids. A conclusion was drawn that the hexaploid plant of Hokkaido should be grouped with the octoploid in one and the same species,Agrostis mertensii Trin.Agrostis mertensii in this amended sense is discussed from a cytogeographical viewpoint.     

DNA ploidy-level variation in native and invasive populations of Lythrum salicaria at a large geographical scale

Aim  This study aimed to document precisely the patterns of DNA ploidy variation in the native and secondary ranges of Lythrum salicaria distribution. The hypothesis that species invasiveness had been induced by a switch in ploidy level was addressed.
Location  Europe, Middle East, North America.
Methods  DNA ploidy levels of 1884 progenies of 578+ plants collected at 124 localities were determined by DAPI flow cytometry.
Results  Large cytotype variation (2 x , 3 x , 4 x and 6 x ) was found across the native area of distribution (64 populations covering 12 European and two Middle Eastern countries). DNA hexaploids were detected for the first time, and rare DNA triploids were reliably confirmed. DNA tetraploids largely prevailed across the native range studied, while DNA diploids and DNA hexaploids were recorded only in Israel and Turkey, respectively. DNA triploid progenies occurred in one population from Hungary (together with DNA tetraploids). Sympatric growth of DNA tetraploids and DNA hexaploids was repeatedly encountered in Turkey. In contrast, cytotype uniformity was a typical feature of the invasive North American plants. Sixty populations, covering 13 states of the USA and provinces of Canada, were characterized by the presence of only DNA tetraploids.
Main conclusions  Several L. salicaria cytotypes (2 x , 3 x , 4 x , 6 x ) occur in the native range of distribution, with much variation concentrated in the Middle Eastern countries, whereas only DNA tetraploids appeared to occur in North America. Our data show that the invasive spread of North American populations was not triggered by differences in ploidy level. Alternative explanations should be sought.     

A cytogenetic study of Eriophyllum confertiflorum (Compositae,Helenieae)

Meiotic analyses of 176 plants from 130 populations of Eriophyllum confertiflorum var. confertiflorum showed that diploids (n = 8) and tetraploids were about equally frequent and that hexaploids and octoploids were rare. Supernumerary chromosomes were found in 14% of the individuals; other meiotic aberrations were uncommon. Eriophyllum confertiflorum var. tanacetiflorum is octoploid. Migration from southwest North America, tolerance of aridity, and spontaneous origin of polyploids may explain the nonrandom distribution of cytotypes in E. confertiflorum var. confertiflorum. Artificial intravarietal crosses of E. confertiflorum var. confertiflorum yielded vigorous, bivalent-forming progeny with mean pollen stainabilities of 41%-96% and 88%-90% at the diploid and tetraploid levels, respectively. Tetraploid x diploid crosses gave triploids in one case and tetraploids in another. The progenies of some artificial crosses between distant populations of E. confertiflorum var. confertiflorum had significantly lower rates of germination and pollen viability.