Genetic relationship between tetraploids and pentaploids in the agamospermous species Taraxacum albidum Dahlst., clarified by enzyme electrophoresis

In order to reveal the genetic relationship of tetraploids and pentaploids in the agamospermous species Taraxacum albidum Dahlst., an allozyme study was carried out. Approximately 200 plants putatively identified as T. albidum were collected mainly from the Kyushu Island of Japan, and analyzed by enzyme electrophoresis. Two multilocus genotypes at 14 presumptive loci of nine enzymes, Type A and Type B, were detected. Most of the sample plants showed uniclonal Type A, which corresponds to “T. albidum” as reported in our previous paper. Type B, which is also uniclonal, was found at fewer localities and was clearly different from Type A in the allele composition of pgi-2 and pgm-1, as well as in the allele dosage at mdh and sod-1. By means of flow cytometry and chromosome count, the ploidy levels of Type A and Type B were shown to be pentaploid and tetraploid, respectively. A comparison of the allele composition suggests a hybrid origin of pentaploid T. albidum (Type A) from an unreduced gamete of Type B and a reduced gamete of any diploid Taraxacum species.     

Distribution of Sexual and Agamospermous Populations of Eupatorium (Compositae) in Asia

Abstract Examinations of chromosome number voucher specimens show that sexual diploid and agamospermous polyploid plants of Eupatorium in Asia can be distinguished by morphology, fertility, and stainability of pollen grains. Using these criteria, reproductive systems (sexual vs. agamospermous) were estimated for 558 herbarium specimens of Eupatorium in East Asia. Of 22 taxa examined, six included both sexual and agamospermous specimens; those of one taxon were all agamospermous; and those of 15 taxa were all sexual. This result shows that 21 taxa are not agamospermous microspecies but are differentiated at the diploid level. Sexual populations of most taxa had restricted geographical distributions. Eupatorium chinense var. chinense and var. oppositifolium consisted of both sexual and agamospermous populations. Sexual populations of these two varieties were allopatric and distinct in external morphology, suggesting differentiation at the species level. The specimens of E. heterophyllum s. str. were all agamospermous, while those of E. mairel , often treated as synonymous with E. heterophyllum , were sexual.
In comparing East Asian and North American Eupatorium for the distributional patterns of sexual and agamospermous populations, three differences can be pointed out: (1) Agamospermous plants of autopolyploid origin have evolved in eight species and are widespread in North America; while most agamospermous plants in East Asia may be of allopolyploid origin, have relatively restricted ranges, and are less frequent than the diploid plants with the exception of in E. chinense var. oppositifolium , (2) The number of sexual species with wide range is greater in North America than in East Asia. (3) The number of sexual species with restricted ranges is greater in East Asia than in North America. The results obtained suggest that speciation among the plants of Eupatorium has occurred more recently in East Asia than in North America.     

斑叶蒲公英的核型分析和花粉母细胞的减数分裂观察

采用根尖压片法确定斑叶蒲公英的染色体数目,通过分析斑叶蒲公英核型及花粉母细胞减数分裂过程,以确定其倍性水平。结果表明:(1)斑叶蒲公英根尖细胞染色体数目为32条,核型公式为2n=3x+x′=32=(18m+6sm)+(3m+4sm+1T),属于2A型。(2)斑叶蒲公英花粉母细胞减数分裂为同时型胞质分裂,四分体的排列方式以正四面体型居多,十字交叉型偏少,偶见左右对称型。(3)前期Ι染色体的构型复杂,中期Ι和中期Ⅱ有赤道板外染色体;后期Ι和后期Ⅱ出现落后染色体、染色体桥及断片;后期Ⅱ和末期Ⅱ还出现染色体分离不同步及不均等分裂的现象;四分体时期出现二分体、三分体、含微核的异常四分体及多分体等异常现象。(4)对其花粉进行离体萌发试验,花粉萌发率只有26.3%,说明斑叶蒲公英是异源四倍体,32条染色体不均等的减数分裂异常,造成花粉活性较低。     

Responses of Sexual and Apomictic Genotypes of Taraxacum officinale to Variation in Light

Abstract: The mode of reproduction, sexual or asexual, will influence the way populations respond to selective pressures. This can cause genetic and ecological divergence between sexual and asexual forms of the same species. Here we examine differences in morphology and phenology between sexual and apomictic types of dandelion, Taraxacum officinale. Sexual and apomictic dandelions were collected from a mixed population on the banks of the river Rhine, The Netherlands. Clonal copies of both sexual and apomictic genotypes were planted in an experimental garden under two light levels. Sexual plants flowered four days later on average than apomicts, but the number of capitula was the same. Apomicts had longer leaves and were heavier than sexual plants, especially under shaded conditions. In apomicts plasticity for leaf length and height was larger than in sexuals, but for most other measured traits no differences in plasticity were observed. Trait values of apomicts were within the same range as those of sexual plants.     

Pollen and the Evolution of Arctotideae (Compositae)

Recent molecular studies have elucidated the phylogeny of Compositae tribe Arctotideae, and found it to contain two, well supported, monophyletic subtribes, Arctotidineae and Gorteriinae, as well as some polyphyletic and problematic genera. On the basis of this new information, it may now be possible to identify diagnostic characters and synapomorphies to support the groupings defined within Arctotideae. Pollen characters have been shown to be particularly variable in Compositae. This paper aims to investigate the utility of those characters in the context of recent molecular phylogenies, in order to determine synapomorphic and diagnostic characters in Arctotideae. The pollen of each genus is described, illustrated with scanning electron micrographs, and optimised on a phylogeny of the tribe. Many pollen characters were found to be very informative when considered in the context of the current best estimate of phylogenetic relationships. Pollen morphology provides synapomorphies for clades at a number of hierarchical levels within Arctotideae, including the two subtribes, Arctotidinae and Gorteriinae, the grouping of Eremothamnus and Hoplophyllum, and smaller clades. It also supports the exclusion of Platycarpha from the tribe. The plesiomorphic palynological state for the tribe is discussed. Particular attention is paid to the evolution of different patterns of lophae (surface ridges). A single origin for the lophate condition is proposed as the most parsimonious mode of evolution in Arctotideae.     

Development and characterization of nine new microsatellite markers in Taraxacum (Asteraceae)

This study aims at developing and characterizing new microsatellite primer pairs in Taraxacum officinale auct. to produce polymorphic markers for genetical and evolutionary studies on apomixis in this sexual‐apomictic complex. A total of 24 diploid plants were tested for allelic polymorphism and heterozygosity. Out of nine loci three deviated significantly from the Hardy–Weinberg equilibrium expectations, probably due to the presence of null‐alleles. Successful cross‐species amplification was obtained for all markers in 29 Taraxacum microspecies from five sections.     

Hybridization between European and Asian dandelions ( Taraxacum section Ruderalia and section Mongolica)2. Natural hybrids in Japan detected by chloroplast DNA marker

Natural hybridization in Taraxacum between native sexual diploids and introduced agamospermous triploids occurring in Japan was studied by means of chloroplast DNA (cpDNA) marker. We first determined the nucleotide sequences between trnT (UGU) and trnF (GAA) of cpDNA for 22 plants obtained from Japan and Europe. The sequences analyzed were about 1,574 base pairs long. Among all accessions, the total numbers of polymorphic characters were 56 nucleotide substitutions, three insertions/deletions (ins/dels), and one repeat number polymorphism of mononucleotide motif. Of these polymorphic characters, four nucleotides and one ins/del were applicable in the discrimination between Japanese and European taxa of dandelions. We selected the ins/del in an intergenic region between trnL (UAA) 3′ exon and trnF (GAA) as a cpDNA marker. Using a newly developed cpDNA marker, 225 plants of putative Taraxacum officinale collected from 11 populations in Niigata City were investigated. Eighty-two percent of them showed a Japanese haplotype of cpDNA, and they were regarded as hybrids. Compared with the previous studies, it is likely that the prevalence of the hybrid plants is a general phenomena at least in urban areas in Japan. The validity of the cpDNA marker for screening Taraxacum hybrids is discussed. Electronic Publication     

Development and characterization of microsatellite markers in the sexual-apomictic complex Taraxacum officinale (dandelion)

 Microsatellite markers were developed in Taraxacum officinale to study gene flow between sexual and apomictic plants and to identify clones. Twenty five thousand genomic DNA clones were hybridized with a (CT)₁₂D probe. The density of (GA/CT) _n repeats was estimated at one every 61 kb in the T. officinale genome, which translates to 13 500 repeats per haploid genome. Ninety two percent of 110 positive clones sequenced contained at least one (GA/CT) _n≥5 repeat. Sixteen (CA/GT) _n≥5 and 11 (AT) _n≥5 arrays were also found in these sequences, suggesting some clustering of dinucleotide repeats. Among 50 PCR primer pairs tested, 32 produced bands and 28 of them were polymorphic. Of these polymorphic markers, 15 were putatively single-locus and the other 13 produced only polymorphic fingerprints. Six loci were further characterized for polymorphism and showed between 6 and 32 alleles per locus. Among eight primer pairs used to analyze the progeny of a sexual cross, seven were co-dominant single-locus Mendelian markers, but one (MSTA10) gave a dominant pattern in accordance with the hypothesis of a null allele segregating in a Mendelian fashion. Three pairs of loci among 28 showed significant linkages of 10, 21, and 39 cM. Observed and expected heterozygosities in two sexual populations indicate that null alleles may be present at two loci, including MSTA10. Received: 4 November 1997 / Accepted: 12 February 1998     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树( Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg)是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草( Taraxacum kok-saghyz Rodin)根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年(1931 - 2018)来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

蒲公英提取液调整小鼠肠道菌群并延长荷瘤生存时间的研究

目的研究蒲公英在调节肠道菌群和改善荷瘤小鼠生存质量提高生存率方面的作用。方法用肝癌腹水瘤H22细胞株注射小鼠造荷瘤小鼠模型,然后口服蒲公英提取液治疗。观察治疗前后菌群变化、腹水量和荷瘤生存时间等。结果蒲公英治疗组与阴性对照组比较,肠道菌群趋于平衡、腹水出现时间延迟、腹水量降低和荷瘤生存时间延长。结论蒲公英提取液能调节小鼠肠道菌群,改善荷瘤小鼠生存质量、提高生存率。     

Peroxidase Phenotypes of Eupatorium mohrii and E. scabridum (Compositae), Widespread All-agamospermous "Species" in the Southeastern United States

Abstract Peroxidase phenotypes of two all-agamospermous "species" of Eupatorium in the southeastern United States were examined. The result supported a hybrid origin ( E. recurvans × E. rotundifolium ) for E. scabidum and an autopolyploid origin from E. recurvans for E. mohrii. Notable variations of E. scabridum in its leaf morphology and peroxidase phenotype were suggestive of occasional sexuality in this agamospermous "species".     

Reproductive success and clonal genetic structure of the rareArnica montana (Compositae) in The Netherlands

In a medium-sized population ofArnica montana, a threatened species in The Netherlands, the breeding system, reproductive success and genetic clonal structure were studied. Pollination experiments suggested thatA. montana is largely self-incompatible. Inbreeding depression was observed for seedling weight but not for fruit weight and germination rate. Although genetic variation is rather low in this population, the data suggest an outcrossing mating system. Analysis of the genotype of all mapped rosettes in a plot of 100 m² indicated that dense clusters often consist of identical genotypes, suggesting a clonal structure. Open clusters frequently contained several different genotypes. This may be caused by limited fruit dispersal, since seedlings were found mainly within or in the near surroundings of the clusters.     

Electrophoretic Study of Taxonomic Relationships in the Saussurea nipponica Complex (Compositae)

Abstract The Saussurea nipponica complex was examined with enzyme electrophoresis. Earlier morphological evidence suggested that the complex comprises S. sugimurai and seven subspecies of S. nipponica . Electrophoretic evidence supports the separation of the two species and the subspecies classification of S. nipponica . Nei's genetic distance ( D = 0.19) between S. sugimurai and S. nipponica exceeds the estimated infraspecific level. Saussurea nipponica is newly defined as a species composed of seven infraspecific taxa which have their own distribution ranges and habitats. They are in a very early stage of differentiation. The extensive morphological diversity in S. nipponica is presumed to be a result of geographical isolation under strong environmental selection.     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树（Hevea brasiliensis（Willd.ex A.Juss.） Muell.Arg）是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草（Taraxacum kok-saghyz Rodin）根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年（1931-2018）来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

Pollen morphology and its taxonomic significance in the tribe Gochnatieae (Compositae, Gochnatioideae)

In the context of recent molecular phylogenies of the basal grades of Compositae, we investigated the utility of pollen morphology within the tribe Gochnatieae. The pollen of 64 species of Anastraphia, Cnicothamnus, Cyclolepis, Gochnatia, Pentaphorus, and Richterago was studied using light microscopy and scanning electron microscopy. In addition, three extra-Gochnatieae genera (Ianthopappus, Leucomeris, and Nouelia) were examined as they were traditionally morphologically related to members of the tribe Gochnatieae. Three of the species of Gochnatieae were examined using transmission electron microscopy. Two pollen types, and two new subtypes, have been recognized on the basis of the pollen shape, size, and exine sculpture. The pollen features of Gochnatia sect. Moquiniastrum and G. cordata are similar and distinctive within the genus and support the recently re-circumscribed section Hedraiophyllum. Within the species with echinate pollen surface, the distinctive spine length of Anastraphia supports its recent resurrection as a genus. The identity of Pentaphorus could not be supported by pollen features as was for other morphological characteristics. The pollen features shared across Cyclolepis, Ianthopappus, Leucomeris, Nouelia and Gochnatia sect. Moquiniastrum, as well as those shared by Richterago and Anastraphia could be a result of parallel evolution.     

Sexual expression and genetic diversity in populations of Cryptogramma crispa (Pteridaceae)

The reproductive biology of Cryptogramma crispa, a tetraploid species with a broad circumboreal and alpine distribution, growing mainly in siliceous boulder fields and crevices, was studied in the laboratory by growing gametophytes in plates with both solidified agar media and sterilized soil. In addition, an electrophoretic study of isozymes was carried out on frond samples from five natural populations, as an additional source of evidence concerning the breeding system and the genetic structure of sporophyte populations. Populations throughout the Iberian range of the species were selected for this study, and a Scottish population was included to represent plants from outside our local area and ecology. The morphological development of gametophytes is of the Adiantum type. All multispore cultures developed into a bigametophytic system, consisting in most cases of male and female prothalli. This pattern of sexual expression provides evidence for outcrossing as the main breeding system in this species. Moreover, there is good evidence that the species possesses an antheridiogen system to promote outcrossing. The long time needed by gametophytes to produce gametangia, and afterwards to fertilize and produce sporophytes, might be the primary reason why so few young sporophytes are found in the wild. The values of the percentage of polymorphic loci and the similarity levels obtained from the isozyme analyses indicate a level of genetic variability that would be expected in an outcrossing species. All these characteristics are usually associated with diploid fern species rather than polyploid species.     

Pollen Morphology and Generic Phylogenetic Relationships in Ophiopogonoideae (Liliaceae)

In the present work, pollen grains of 3 species of Liriope, 24 species of Ophiopogon and 2 species of Peliosanthes were examined under scanning electron microscope, Among them 4 species were also observed under transmission electron microscope. The observation (Table 3)shows that Liriope and Ophiopogon distinctly differ from Peliosanthes in the exine ornamentation and structure, They may be divided into two types: 1. Rugulate-perforate, ektexine with perforate tectum in Liriope and Ophiopogon. 2. Verrucate, Verracae unequal in size, ektexine intectate in Peliosanthes. Pollen morphology shows the close affinity between Liriope and Ophiopogon, but they are very far from Peliosanthes. The correlation between pollen and gross morphology in Liriope, Ophiopogon and Peliosanthes are stated and their evolutionaly trends are discussed in this paper. The pollen characters support the placement of Liriope and Ophiopogon in one tribe—Ophiopogoneae, and Peliosanthes in another tribe—Peliosantheae. Peliosanthes is more advancedthan Liriope and Ophiopogon.