Physical localization of rRNA genes by fluorescence in situ hybridization (FISH) and analysis of spacer length variants of 45S rRNA (slvs) genes in some species of genus Sesbania

The somatic chromosome numbers 2n = 12 in S. macrantha, S. coerulescens and 2n = 24 in S. simplicuscula were determined, additionally the contradictory chromosome numbers of S. bispinosa (2n = 12, 13, 14, 24) and S. pachycarpa (2n 12, 14) were determined as 2n = 24 and 2n = 14, respectively. The number of 5S rDNA sites in chromosome pair 1 was highly conserved in all the diploid and tetraploid species studied irrespective of their geographic distribution, suggesting that all diploid and tetraploid species/cytotypes of Sesbania analyzed in the present study are in close proximity. Cytogenetic mapping of the 45S multi-gene family was also carried out using fluorescence in situ hybridization. 45S rDNA was consistently located on short or long arms of two sub-metacentric chromosome pairs except on one chromosome pair in S. macrantha and on three chromosome pairs in S. bispinosa and S. cannabina. Out of these nine species, we observed the homogenization of intergenic spacer in six species and find only one spacer length variant (slv) located on one to three chromosome loci. However, three of the species were observed to have two slvs located on two different chromosomes. The species were grouped as per their evolutionary relationship on the basis of the results of the present study.     

Cytotaxonomy ofCalliphoridae (Diptera)

A modification of the general system of classification ofCalliphoridae is proposed in this report. Information about the chromosome complements of about 90 species is provided including references to the earlier literature on chromosomes of this family. With one exception all species studied by us or by earlier investigators have 2n=12. The total complement length of 556 complements from 83 species averaged 66.4 μ. Most species have a short heteromorphic sex pair but the size and morphology vary considerably and one species,Hemipyrellia fernandica, seems to have a quadrivalent sex-chromosome complex in a 2n=14 complement. The autosomal pairs vary in both length and arm ratios between the species but seem to be more stable than the sex chromosomes. Only minor variations were found between different collections of the same species except for two collections ofCalliphora croceipalpis. Although presently available data on the chromosomes of Diptera species suggest that increases in total complement length accompany evolutionary progress, no such general trends were obvious in either the total complement lengths or chromosome morphology, either within or between the tribes ofCalliphoridae. Thus the karyotypical reorganizations in the family have apparently not been directly associated with changes in the general morphological features of the adults which may have responded in these respects more extensively to genetic mutations.     

Chromosome numbers in some North American species of the genus Cirsium. III. Western United States,Mexico, and Guatemala

New data are presented on chromosome numbers for 36 species, two varieties, and two hybrids ofCirsium (Compositae). These include first reports forC. rhothophilum (2n = 34),C. andrewsii (2n = 32),C. crassicaule (2n = 32),C. quercetorum (2n= 32, 112),C. pascuarense (2n= 32),C. douglasii var.canescens (2n = 30, 34),C. hydrophilum (2n = 32),C. neomexicanum (2n = 30),C. cymosum (2n = 30, 34),C. acantholepis (2n= 34),C. radians (2n = 34), C.grahami (2n = 32),C. nigriceps (2n = 36),C. andersonii (2n= 32, 64),C. anartiolepis (2n = 34), andC. subcoriaceum (2n= 34). The published data on chromosome numbers of Eurasian and AmericanCirsium are summarized. In Eurasia, speciation has taken place primarily at the diploid level but is occasionally reinforced by polyploidy. The ancestral base number of 17 has been preserved in almost all species, and there is little evidence that reduction in chromosome number has played a significant role in speciation. In America speciation has proceeded exclusively at the diploid level, but the ancestral genome of 17 chromosomes has been retained in only about half of the species examined. In the remaining species, restructuring of the genome has occurred resulting in a reduction in number from 17 to 9 in extreme cases. Polyploidy, when seen, is of no significance. It is suggested that all species with greatly reduced numbers may represent products of a single reduction series.     

华南地区3种兔儿风属植物(菊科-帚菊木族)的细胞学研究

首次报道了华南地区兔儿风属(Ainsliaea DC.)(菊科-帚菊木族Asteraceae-Pertyeae)3种植物共4个居群的染色体数目和核型。其中长穗兔儿风(A.henryi Diels)的染色体数目为2n=24,核型公式为2n=16m+8sm;三脉兔儿风(A.trinervis Y.C.Tseng)的染色体数目为2n=26,核型公式为2n=16m+10sm;莲沱兔儿风(A.ramosa Hemsl.)2个居群的染色体数目均为2n=26,核型公式为2n=26=22m+4sm。所有居群的染色体由大到小逐渐变化,核型没有明显的二型性。这些结果表明兔儿风属植物确有x=12和x=13两个基数,其中x=13可能是该属的原始基数。     

Characterization of B chromosomes in Lilium hybrids through GISH and FISH

Supernumerary (B) chromosomes and small aberrant chromosomes were detected in Lilium hybrids and characterized through genomic in situ hybridization (GISH) and florescence in situ hybridization (FISH). Two small, supernumerary or B chromosomes were detected as extra chromosomes in a tetraploid plant derived from chromosome doubling of a hybrid (2n = 2x = 24) between a cultivar of the Longiflorum (L) and the Trumpet (T) group. When this tetraploid LLTT hybrid was crossed with a triploid LLO hybrid (O = Oriental), the B chromosome was transmitted to 73.4 % of the progenies. Based on GISH and FISH characterization, it was shown that the B chromosome consisted of two identical arms, with 5S rDNA hybridizing to the majority of it, which were flanked by normal telomeres, suggesting that this is an isochromosome. In another population, which is a backcross progeny between a F1 hybrid of Longiflorum × Asiatic (LA) and its Asiatic parent, the former produced functional 2n gametes which resulted in a triploid LAA progeny (2n = 3x = 36), in which three exceptional plants possessed 35 normal chromosomes and a small aberrant chromosome instead of the expected normal number of 36. In all three cases, the small aberrant chromosomes were isochromosomes which had obviously originated during the first backcross generation. These three chromosomes showed normal telomeres and mitosis. In addition, one of the new generated chromosomes possessed two 45S rDNA sites in the proximal positions. These new arisen isochromosomes were proposed to originate from centric breakage and fusion of two short arms of the missing chromosome in three genotypes, respectively, based on the comparison of arm lengths as well as rDNA loci. Their relevance to the origin of Bs is discussed.     

Combining FISH and model-based predictions to understand chromosome evolution in Typhonium (Araceae)

Background and Aims

Since the advent of molecular phylogenetics, numerous attempts have been made to infer the evolutionary trajectories of chromosome numbers on DNA phylogenies. Ideally, such inferences should be evaluated against cytogenetic data. Towards this goal, we carried out phylogenetic modelling of chromosome number change and fluorescence in situ hybridization (FISH) in a medium sized genus of Araceae to elucidate if data from chromosomal markers would support maximum likelihood-inferred changes in chromosome numbers among close relatives. Typhonium, the focal genus, includes species with 2n = 65 and 2n = 8, the lowest known count in the family.

Methods

A phylogeny from nuclear and plastid sequences (96 taxa, 4252 nucleotides) and counts for all included species (15 of them first reported here) were used to model chromosome number evolution, assuming discrete events, such as polyploidization and descending or ascending dysploidy, occurring at different rates. FISH with three probes (5S rDNA, 45S rDNA and Arabidopsis-like telomeres) was performed on ten species with 2n = 8 to 2n = 24.

Key Results

The best-fitting models assume numerous past chromosome number reductions. Of the species analysed with FISH, the two with the lowest chromosome numbers contained interstitial telomeric signals (Its), which together with the phylogeny and modelling indicates decreasing dysploidy as an explanation for the low numbers. A model-inferred polyploidization in another species is matched by an increase in rDNA sites.

Conclusions

The combination of a densely sampled phylogeny, ancestral state modelling and FISH revealed that the species with n = 4 is highly derived, with the FISH data pointing to a Robertsonian fusion-like chromosome rearrangement in the ancestor of this species.     

Cytotaxonomic study of theVicia cracca complex 1. Czechoslovak taxa

Three races ofVicia cracca L. have been found on the territory of Czechoslovakia, two with the chromosome number 2n=14 and one with 2n=28. Diploid races seem to be more primitive and are less widely distributed. They occur mostly in the primary communities while the tetraploid race is very plastic in the ecological respect and is common both in primary and secondary communities. These races are characterized by some morphological and ecological features. As far as the vertical distribution is concerned, one of the diploid races and the tetraploid occur mostly in the lowland and in the colline zone, the second diploid race has a mountain character. The related tetraploid speciesVicia oreophila ?ertová, with the chromosome number 2n=28 is distributed at similar altitudes.     

Genetic system relationships inTrifolium

Examination of species of Trifolium in the Kentucky collection revealed that annual species generally have simple tap roots, low chromosome numbers (2n = 10?32), are usually self-pollinating and many were introduced from a Mediterranean type climate. Perennial species generally are tap-rooted, stoloniferous, or rhizomatous, possess higher chromosome numbers than annuals (2n = 12? 130), are mostly cross-pollinating and do not have specific climate-habitat relationships. Species introduced from Eurasia are more numerous and more diverse in base chromosome number (n = 5?8) than from other origins. Only species with diploid chromosome numbers of 16 or higher are stoloniferous or rhizomatous. Rhizomatous species, mostly cross-pollinated, were introduced from Eurasia, North and South America, but not from Africa, and not often from Mediterranean climates. Self- and cross-pollinated species occur in all origins. Different flower colors and leafmarks are not associated with origins, climates, and other morphological and physiological characteristics.     

The origin of the North Indian sugarcanes

The “North Indian sugarcanes”, cultivated by Indian peasants during many centuries, have been studied morphologically very exactly byC. A. Barber from 1910 to 1920. They were named “Saccharum Barberi” byJeswiet. Barber distinguished four groups. In 1931 the present author found the following chromosome numbers in these groups: 2n=116 and 2n=82 in the Sunnabile group; 2n=82 in the Mungo group; 2n=124 and 2n=107 in the Nargori group and about 91 in the Saretha group. The first three groups are sterile, the last is fertile. It is shown that the North Indian sugarcanes are hybrids between ancient indigenous sugar canes with a basic number of 17 chromosomes, and forms ofS. spontaneum withn=40,n=48 andn=56 respectively. Differences in the numbers of chromosomes contributed by the mother type may in part have their origin in endo-duplication, as commonly observed inSaccharum hybrids. Details are presented in Table 2. The differences found between different forms of IndianS. spontaneum in respect to chromosome number, sugar content and mosaic resistance may be attributed to intercrossing with canes of the fertile Saretha group.     

Studies of the morphology of chromosomes of some selected species

Karyotypes of twelve species from twenty-four localities in southern Moravia and one locality in Slovakia were investigated. Their counts or karyotypic formulae are as follows:Chenopodium foliosum (Moench) Ascherson: K (2n)=18=16 A^m+2 B^sm;Astragalus austriacus Jacq.: K (2n)=16=8 A^m+8 B^sm;Astragalus exscapus L.: K (2n)=16=10 A^m+4 B^sm+2 C^st;Astragalus cicer L.: K (2n)=64;Astragalus onobrychis L.: K (2n=64 and K (2n)=64+1;Vicia dumetorum L.: K (2n=14=10 A^m+4 B^sm;Vicia sylvatica L.: K (2n)=14=2 A^m+10 B^sm+2 C^st;Vicia pisiformis L.: K (2n)=12=8 A^m+4 B^sm;Vicia cassubica L.: K (2n)=12=4 A^m+6 B^sm+2 C^st;Vicia cracca L. (from five localities in southern Moravia): K (2n)=28=4 A^m+12 B^sm+12 C^st and K (2n)=28+1=5 A^m+12 B^sm+12 C^st;Vicia cracca L. (from one locality in Slovakia): K (2n)=14=2 A^m+6 B^sm+6 C^st;Vicia tenuifolia Roth: K (2n)=24=4 A^m+16 B^sm+4 C^st;Serratula lycopifolia (Vill.) Kern.: K (2n)=60.     

Comparative cytomolecular analyses reveal karyotype variability related to biogeographic and species richness patterns in Bombacoideae (Malvaceae)

Bombacoideae is one out of nine subfamilies of Malvaceae and encompasses 160 tree species. The subfamily is karyotypically characterized by small and numerous chromosomes and is traditionally known by a remarkable inter- and intraspecific chromosome number variation. We conducted a comparative cytogenetic analysis to investigate karyotype diversity and chromosome evolution within Bombacoideae. To achieve this, we performed new chromosome counts, CMA/DAPI double staining, genome size estimations, and localization of 5S and 45S rDNA by fluorescence in situ hybridization for 21 species distributed across the Bombacoideae phylogeny. We performed ancestral states reconstruction analyses to elucidate chromosome evolution and provide insights into the systematics and evolution of Bombacoideae in comparison with other Malvaceae species. Newly generated data on chromosome number on Bombacoideae revealed diploids (Ochroma (2n = 84), Cavanillesia, Pochota, Pseudobombax (2n = 88), and Pachira (2n = 92)) and polyploids (Adansonia digitata (2n = 160) and Eriotheca species (2n = ca. 194 and 2n = 276)). For most species, in situ hybridization revealed karyotype, with two pairs of 45S rDNA sites co-located with CMA⁺ bands, and 5S rDNA sites in only one chromosome pair. Taken together, our results provide support to the hypothesis of karyotypic stability in Bombacoideae. Only the Pachira s.l. clade displayed some variability in ploidy level, number of CMA⁺ bands and 45S rDNA sites, and genome size compared to other Bombacoideae clades. The Striated bark clade was characterized by comparatively small genomes and low cytomolecular variability. Karyotypic data were related to biogeographic and species richness patterns of Bombacoideae.     

Chromosome numbers,polyploidy, and hybridization in castilleja (scrophulariaceae ) of the Great Basin and Rocky Mountains

Chromosome numbers are reported for 190 collections ofCastilleja of the Great Basin-Rocky Mountains and adjacent regions in western North America. Polyploidy has played a major role in evolu tion of this genus. Of the 35 taxa represented, 14 are exclusively diploid (n =12). The remaining 21 taxa exhibit polyploidy: eight are tetraploid only, two are octopIoid only, while 11 of the more wide-ranging species have two or more levels of polyploidy. BothC. rhexifolia andC. sulphured have diploid, tetraploid, and octoploid races while the widespreadC. miniata has four (2x, 4x, 8x, and 10x). Where appropriate, the role of polyploidy and hybridization inCastilleja evolution and their relevance to taxonomy are discussed for individual species.     

Chromosome numbers and their taxonomic implications for eight Brazilian andropogons (Poaceae: Andropogoneae)

Eleven chromosome counts are reported for Brazilian populations of eight species ofAndropogon. Counts for five of the species are first reports for the species. Four of these species,A. arenarius, A. glaziovii, A. lateralis, andA. lindmanii, are hexaploids (n=30) and belong to a group of about a dozen species informally referred to as theAndropogon lateralis complex. Two other species of this complex,A. bicornis andA. hypogynus, we also found to be hexaploids, in agreement with previous reports. Diploid counts (n=10) forA. macrothrix (a first report) andA. virgatus (the same as two previous reports) support the morphological affinities of these two species to other species complexes withinAndropogon.     

Cytological studies on three species of neotropical cassidines (Coleoptera,Chrysomelidae)

Chromosome numbers, meiosis and sex-determining mechanisms of three species of Chrysomelidae (Coleoptera) were studied. They belong to the tribe Stolaini of Neotropical Cassidinae. Stolas lacordairei and Botanochara sp. have high chromosome numbers (2n=30♂), the first with a primitive coleopteran sex chromosome system Xy _p and the other with a very complex one X _p ¹ X _p ² neo Xneo Y. Botanochara bonariensis shows an even higher chromosome number (2n=44♂) and multiple sex chromosomes as does B. sp. The possible tendencies in the karyological evolution of the Stolaine Cassidines are discussed.     

The chromosome morphology ofHesperis matronalis subsp.matronalis and related diploid taxa

Hesperis matronalis L. subsp.matronalis contains various genoms having the same chromosome number (2n=24), differing, however, by ther-index of some pairs of homologous chromosomes. Diploid sets of the taxaHesperis matronalis L. subsp.matronalis, Hesperis sylvestris Crantz subsp.sylvestris, Hesperis sylvestris Crantz subsp.velenovskyi (Fritsch) Borza andHesperis steveniana DC. are compared.     

Cytology of SW Asian Chenopodiaceae: new data from Iran and a review of previous records and correlations with life forms and C<Subscript>4</Subscript> photosynthesis

The mitotic chromosome numbers of 35 species belonging to 25 genera from East Azerbaijan Province of Iran and meiotic numbers of five species of Salicornia from different parts of Iran of family Chenopodiaceae are reported. Some of them are first reports and some are first counts from Iran. Based on a review of previously published reports, 145 species and 46 genera occurring in SW Asia have been cytologically studied either based on populations within or surrounding regions. The nomenclature and generic position of all these species are updated based on recent phylogenetic and taxonomic studies. The polyploidy percentage of 26.2 % is beyond the average known in flowering plants, which is surprising for dominant plants of saline and desert ecosystems. The polyploidy of annual plants is only 16 % and that of perennials 19 %, respectively. It was found that C₄ plants represent lower polyploidy levels than C₃ plants. This is correlated by the fact that large number of annuals in the area is C₄ and secondly, polyploidy may constrain niche advantageous in C₄ plants. However, presence of different cytotypes in the widespread species is advantageous as they can occupy different niches. The basic chromosome numbers in chenopods is x = 9 with few derived exceptions in Spinacia (x = 6), Camphorosma (x = 6) and some species of Petrosimonia (x = 8).