COMPOSITION OF VOLATILES IN RELATION TO TAXONOMY OF AMERICAN ALLIUMS

The North American species of Allium exclusive of A. schoenoprasum and A. tricoccum of Old World affinity are grouped on the basis of morphological similarity into eight discontinuous species alliances typified by A. acuminatum, A. campanulatum, A. canadense, A. cernuum, A. falcifolium, A. kunthii, A. sanbornii, and A. validum, respectively. Representatives of each of these alliances were compared with respect to volatile constituents responsible for characteristic odors by means of gas chromatography. Results indicate that these volatiles provide evidence of relationship useful in the classification of alliums. Uniformity was found in composition of volatiles in the representatives of the A. canadense, A. cernuum, A. kunthii, and A. sanbornii alliances. Variation was observed in the A. acuminatum, A. campanulatum, and A. falcifolium alliances. A. validum was the only species of its alliance studied. Vapors of A. validum contain mostly n-propyl sulfides (onion-like odor) as does the cultivated A. cepa. Methyl sulfides (cabbage-like odor) predominate in the A. sanbornii alliance. A few species of the A. acuminatum and A. falcifolium alliances contain mainly allyl sulfides (garlic-like odor).     

Phylogeny of Allium L. subg. Melanocrommyum (Webb et Berth.) Rouy based on DNA sequence analysis of the internal transcribed spacer region of nrDNA

 Sequence analysis of the ITS region of nuclear ribosomal DNA from subgeneric representatives of Allium L. produced phylogenetic trees which concurred with previous conclusions based on classical taxonomy. Phylogenetic analysis revealed a closer relationship between Nectaroscordum siculum and Allium cernuum (representing Amerallium) than between A. cernuum and the rest of the Allium species employed in this study. The phylogeny of subg. Melanocrommyum based on ITS sequences largely agreed with inferences made by previous researchers based on morphology or a restriction analysis of chloroplast DNA. However, the phylogenetic positions of Allium protensum and Allium macleanii based on ITS sequences did not correspond to their morphological similarity with Allium schubertii and Allium giganteum, respectively. Received: 15 February 1998 / Accepted: 12 March 1998     

A new species of Allium (Liliaceae)

Allium stoloniferum, a new species from southern Mexico, belongs to theA. kunthii alliance on the basis of the appearance of the perianth segments and the presence of long slender rhizomes, but differs by the presence of bulbils.     

CYTOLOGY OF SOME WESTERN CANADIAN ALLIUM SPECIES

Cytology of four species of Allium from western Canada was studied. Three species viz: A. acuminatum 2n = 14, A. cernuum 2n = 14, and A. schoenoprasum 2n = 16 were found to be diploids with normal meiosis. Some populations of A. cernuum and A. schoenoprasum contained a high number of B-chromosomes. Diploid (2n = 14) and tetraploid (2n = 28) populations were encountered in A. textile. While the diploid meiosis was regular, the tetraploids showed 1–5 quadrivalents at metaphase I, suggesting their possible autoploid origin.     

GIEMSA C-BANDED KARYOTYPES OF SEVEN NORTH AMERICAN SPECIES OF ALLIUM

The karyotypes of seven North American Allium species were studied by Giemsa C-banding technique. Two species (A. shoenoprasum and A. tricoccum) were diploids with 2n = 16 chromosomes. Three species (A. cernuum, A. douglasii and A. geyeri) were also diploids but with 2n = 14 chromsomes. Diploid and tetraploid populations of A. textile (2n = 14, 28) were studied. The population of A. canadense studied here was a tetraploid (2n = 28). All these North American species, except A. geyeri, possessed centromeric bands in all their chromosomes and nucleolar constriction bands in their satellited chromosomes. Allium shoenoprasum contained telomeric bands in most of its chromosomes but the other species had them only in a small number of chromsomes. Only three species (A. shoenoprasum, A. textile and A. tricoccum) were found to have intercalary bands in some chromosomes. The heterochromatin distribution in B chromosomes of three species was also observed. In A. cernuum, the heterochromatin occupied most of the length of all its Bs, but in A. shoenoprasum, heterochromatin was concentrated in the centromeric region. One population of A. textile (CC1179) was found to have a B chromosome in which very little heterochromatin existed.     

Evolution of genome size inAllium (Alliaceae)

The 4C DNA amounts of 86 species fromAllium subgg.Allium, Rhizirideum, Bromatorrhiza, Melanocrommyum, Caloscordum andAmerallium show a 8.35-fold difference ranging from 35.60 pg (A. ledebourianum, 2n = 16) to 297.13 pg (A. validum 2n = 56). At diploid level the difference is 3.57-fold betweenA. ledebourianum (35.60 pg) andA. ursinum (127.14 pg). This shows that a significant loss and/or gain of DNA has occurred during evolution. On average subgg.Rhizirideum andAllium have less DNA amount than subgg.Melanocrommyum andAmerallium. The distribution of nuclear DNA amounts does not show discontinuous pattern and regular groups. The evolution of genome size has been discussed in relation to polyploidy and genomes, heterochromatin, adaptive changes in morphological characteristics, phenology and ecological factors, and infrageneric classification.     

VARIABILITY OF ACCESSORY CHROMOSOMES IN NATIVE POPULATIONS OF ALLIUM CERNUUM

Grun , Paul . (Penn. State U., University Park.) Variability of accessory chromosomes in native populations of Allium cernuum. Amer. Jour. Bot. 46(3) : 218-224. Illus. 1959.—Small euchromatic accessory chromosomes, which lack visible constrictions, have become established in native populations of nodding onion, Allium cernuum Roth. Variant types, including large accessories, and a form having a visible metacentric constriction, also occur, although more locally restricted in distribution. The accessories show a strong tendency towards non-disjunction in mitotic divisions, resulting in a variability of number in different cells within and between root tips and in different microsporocytes of each plant. The metacentric chromosome undergoes a normal disjunction. Accessories are not paired at first metaphase of meiosis, and drift to poles at random during first anaphase, a few being lost as micronuclei. During second anaphase they go through the normal equational division. In spite of this mitotic and meiotic irregularity, plants of 11 of 14 separate populations collected in Pennsylvania and West Virginia contained accessories in up to a maximum of 50% of the individuals in the population.     

Interspecific hybridization of Allium giganteum Regel: production and early verification of putative hybrids

 Cut flowers of Allium giganteum Regel were emasculated and maintained in half-strength Murashige and Skoog liquid medium supplemented with 3% sucrose and 1000 ppm each of Agrimycin^R and Benlate^R. Wide hybridization was attempted and, through embryo rescue, putative hybrids were obtained from crosses involving A. cernuum Roth, A. oreophilum C.A. Mey. and A. schubertii Zucc. PCR amplification of the internal transcribed spacer of ribosomal DNA followed by digestion with NdeII generated restriction profiles that confirmed the hybrid nature of the A. giganteum×A. schubertii progenies. The other putative hybrids were found to be products of self pollination. Received: 15 August 1997 / Accepted: 2 September 1997     

GAMETOPHYTES AND SUBGENERIC CONCEPTS IN LYCOPODIUM

A critique of the Freeberg and Wetmore work on cultured Lycopodium gametophytes of L. selago, L. flabelliforme, and L. cernuum is presented. All three gametophytes are shown actually to be L. cernuum based on morphological and anatomical features of their sporophytes. A reassessment of characters in the genus demonstrates the taxonomic validity of the three groups proposed as subgenera within Lycopodium.     

Phylogeny reconstruction and hybrid analysis in Allium subgenus Rhizirideum

Amplified fragment length polymorphisms (AFLPs) for assessing nuclear DNA diversity have been used for the reconstruction of the phylogeny and evolution of several sections of Allium subgenus Rhizirideum. A dataset of 355 characters for 33 accessions belonging to 20 species has been compiled. The band-sharing of five interspecific hybrids and of an F₂ population between Allium cepa and Allium roylei with their parents indicated a heterozygosity level between 6 and 14%, which allows the use of dominant markers such as AFLPs for phylogeny reconstruction. A majority rule consensus tree based on 56 most-parsimonius trees (CI = 0.528) revealed a separate clade for each of the sections, Cepa, Rhizirideum and Schoenoprasum, and one clade combining the sections Oreiprason and Petroprason. An unweighted pair group mean average (UPGMA)-based dendrogram showed the same subdivision. The trees and the ’Hybrid Distance’ approach both supported the assumption of a hybrid origin for A. roylei with considerable subsequent secondary evolution. The establishment of three alliances in the section Cepa and the close relationship of sections Oreiprason and Petroprason are now confirmed. The predictions of the Soybean domestication scenario, i.e. selection of a crop from one progenitor with subsequent narrowing of the genetic diversity of the crop, which applies to the cultigens A. cepa and Allium fistulosum, is supported by the Hybrid Distance approach. Received: 23 August 1999 / Accepted: 14 September 1999     

Autopolyploid induction via somatic embryogenesis in Lilium distichum Nakai and Lilium cernuum Komar

New ornamental varieties of high quality can be created via artificial polyploid induction. In the present study, the first system of polyploid induction with somatic embryogenesis of Lilium distichum Nakai and Lilium cernuum Komar. was developed. Somatic embryos were cultured on MS with 0.41 μmol L^?1 picloram and 1.07 μmol L^?1 NAA by scales (5 mm²). After 40 days, somatic embryos were transferred to MS with 2.21 μmol L^?1 BA for somatic embryogenesis. As determined from observations of paraffin sections, embryonic cells of L. distichum originated from outer cells at first, and somatic embryogenesis occurred through an indirect pathway. In L. cernuum, embryonic cells originated from inner cells at first, and somatic embryogenesis occurred through a direct pathway. Polyploids were successfully formed from somatic embryos and scales by the soaking and mixed culture methods with different colchicine concentrations (0.01%, 0.05%, and 0.1%; v/v) and durations (24, 48, and 72 h). The polyploid induction rate reached 57.14% and 46.15% with 0.05% colchicine treatment in L. distichum (48 h) and L. cernuum (24 h), respectively. Tetraploids (28.57% and 23.08%) and aneuploids without chimeras among the obtained polyploid plantlets were identified by chromosome counts of root-tip tissue squashes in L. distichum and L. cernuum. Tetraploid plantlets of L. distichum exhibited broader leaves, longer guard cells, larger stomata and higher stomatal conductance than diploid plantlets. Tetraploid plantlets of L. cernuum showed 1.76?×?higher chlorophyll content, significantly more leaves, longer guard cells, larger stomata and lower stomatal conductance than diploid plantlets.

     

Giemsa C-banded karyotypes and taxonomic relationships of some North AmericanAllium species and their relationship to Old World species (Liliaceae)

The somatic karyotypes of six North AmericanAllium species and the EuropeanA. scorzonerifolium have been investigated using a Giemsa C-banding technique. All species have a chromosome number of 2n = 14. InA. scorzonerifolium and the three North American speciesA. dichlamydeum, A. fibrillum andA. unifolium C-bands are restricted to two pairs of nucleolar chromosomes. Each chromosome has a band proximal to the nucleolar constriction and a positively banded satellite. InA. acuminatum, in addition to the bands associated with the nucleolar constrictions, all chromosomes also have pericentromeric bands.A. cernuum exhibits a distinctive banding style: two chromosome pairs with bands adjacent to the nucleolar constrictions and four pairs with telomeric bands on their short arms. In the karyotype ofA. geyeri neither C-bands nor nucleolar chromosomes were found.—A comparison of the banding styles together with other cytological and morphological characters of these species with old world members ofAllium reveals:A. cernuum closely resembles species within subgenusRhizirideum, whereas the other species studies exhibit many similarities with subgenusMolium. Their sectional grouping and their relationships with Old World species are discussed.     

Sequence analysis of a chloroplast intergenic spacer for phylogenetic estimates in Allium section Cepa and a PCR-based polymorphism detecting mixtures of male-fertile and male-sterile cytoplasmic onion

Restriction-enzyme analysis of the chloroplast (cp) DNA yielded maternal phylogenies supporting a close phylogenetic relationship among normal (N) male-fertile and male-sterile (S) cytoplasmic bulb onion (Allium cepa), Allium altaicum, Allium fistulosum, Allium galanthum, Allium roylei, and Allium vavilovii. The S cytoplasm of onion is most likely an alien cytoplasm introduced in antiquity into onion populations. We previously showed that size differences in an intergenic spacer in the cp DNA distinguish N and S cytoplasms of onion. We cloned and sequenced this intergenic spacer from the N and S cytoplasms of onion, A. altaicum, A. fistulosum, A. galanthum, Allium pskemense, Allium oschaninii, A. roylei, and Allium ampeloprasm (outgroup) to identify the nature of previously described RFLPs and to develop a PCR-based marker revealing N-cytoplasmic contamination of S-cytoplasmic hybrid seed lots. Phylogenies based on restriction-enzyme analysis of the entire cp DNA were similar, but not identical, to those based on sequence divergence in this intergenic region. Received: 29 November 1999 / Accepted: 28 April 2000     

Variation in overall fitness due to seed source: projections for predictive provenancing

Seed sourcing decisions affect short- and long-term restoration outcomes. Seeds sourced closer to restoration sites are likely to be better adapted to local conditions and therefore may perform better than those sourced farther away, following assumptions of local adaptation. However, plants may not be adapted to future conditions under climate change; hence, managers are considering a predictive provenancing approach, where plant materials adapted to predicted conditions are used at a site. Currently, there is little empirical evidence available to inform this approach. To address this, we evaluate predictive provenancing using three species of forbs used in tallgrass prairie restorations (Allium cernuum, Chamaecrista fasciculata, and Rudbeckia hirta) in a common garden experiment in northeastern Illinois, U.S.A. We compared the fitness in plants sourced from three regional zones across a latitudinal gradient that represents different climate projections, relative to the planting site. Data were analyzed using Aster life-history models and generalized linear models. We found that source affected overall fitness in all three species, but no climate proxy had the highest fitness across all species. The performance at each life stage had different effects on overall fitness, which varied by source. We observed later reproductive phenology in southern-sourced plants for all three species, possibly due to adaptation to longer growing seasons. The mixed results of this study suggest that climate proxy alone would not be sufficient to determine an effective and accurate predictive provenancing strategy. Long-term tests are needed to pursue such a strategy for high-priority species.     

Floral anatomy of Neotropical species of Mayacaceae

The Mayacaceae are a monogeneric monocot family of herbs that grow on swampy areas in the Americas and in Africa. Both the number of species constituting the family and its inter-familial relationships are unclear. By describing and comparing the floral anatomy of Mayaca fluviatilis, M. fluviatilis f. kunthii, M. longipes and M. sellowiana we have identified some features that delimit the species. These include: arrangement of flowers on the stem, shape of stamens, size of apical pores, disposition of microsporangia, number of ovules and shape of the stylar canal. We concluded that M. fluviatilis f. kunthii should be considered as a species (M. kunthii) rather than a forma. Other characters such as number of stamens and microsporangia, placentation, ovule type and cell numbers in the pollen grain support the placement of the Mayacaceae within Poales.     

Chromosome association in one induced and five natural tetraploids of sorghum

A cytological analysis of chromosome association was made inS. miliaceum, S. panicoides, S. almum, S. macrochacta, S. halepense, and an induced autotetraploid ofS. cernuum all with2n=40 chromosomes. The study of pachytene chromosome associations in the first two species revealed their differentiated structure, while in the other species pachytene has not been analysed in detail. Also in their basic morphology they resembled diploid Eu-sorghums. The frequency of partner exchanges among the observed associations of four chromosomes varied from 0 to 2 and they appeared to be distributed all along the length of the chromosomes. Evidence for chromosomal differentiation was recorded and it was suggested that it might bring about increased bivalent synapsis when compared to the situation in the induced autotetraploid ofS. cernuum.Data also indicate thatS. miliaceum has essentially autoploid behaviour and thatS. panicoides is not closely related to any diploid Eu-sorghum. Comparison of the ehromosome behaviour in induced autotetraploidS. cernuum at post-pachytene stages of meiosis with that obtaining inS. almum andS. halepense suggests that the latter specios might have undergone considerable chromosomal differentiation at the same time retaining autoploid behaviour.S. macrochaeta on the other hand, has been classified segmental alloploid.Meiotic irregularities were present to a varying extent and it is considered that genetic factors are also important in determining the ultimate fertility of the tetraploids studied.     

Chromosomal location of rDNA in Allium: in situ hybridization using biotin- and fluorescein-labelled probe

Summary A biotin- and fluorescein-labelled probe of Helianthus argophyllus has been used to map specific repeated rDNA sequences by in situ hybridization on mitotic chromosomes of Alliwn cepa, Allium fistulosum, a diploid interspecific (Allium fistulosum x Allium cepa) F₁ hybrid, and a triploid interspecific (2 x = A. cepa, 1 x = A. fistulosum) shallot. Hybridization sites were restricted to satellited and smallest pairs of chromosomes in both A. cepa and A. fistulosum. The number, size, and position of the hybridization sites distinguish homologous chromosomes and identify the individual chromosomes carrying the nucleolus organizing region (NOR) at the secondary constriction, as well as the individual chromosomes carrying an additional NOR. This in situ hybridization technique is the first reported in a plant species and offers new cytogenetic markers in Allium.     

CYTOEMBRYOLOGY OF ALLIUM TEXTILE NELS. & MACBR.

Root tip mitosis, meiosis, sporogeneses, and the development of gametophytes are described for eight populations of Allium textile Nels. & Macbr., native to Montana. The basic chromosome number is n = 7, with tetraploids being predominant. Of the eight populations studied, only one was composed entirely of diploids (2n = 14). Meiosis is generally normal with bivalents and tetravalents formed during the process. Laggard chromosomes leading to the formation of micronuclei are frequently observed during microsporogeny. The anther wall is five-layered and its development corresponds to the Monocotyledonous type. The tapetum is glandular and its cells remain uninucleate throughout microsporogeny. The adjacent anther locules coalesce before dehiscence. Pollen grains are shed at the three-celled stage. A stomium is organized. Ovules are anatropous, tenuinucellar and bitegminal. The archesporial cell develops directly into a megasporocyte. Development of the female gametophyte is bisporic and corresponds to the Allium type. These observations support Traub's classification (1975) on Allium.     

SELECTIVE INHIBITION OF CELL CYCLE STAGES IN THE ALLIUM ROOT MERISTEM BY COLCHICINE AND GROWTH REGULATORS

The treatment of root tips of Allium carinatum, Allium cepa, and Allium flavum with colchicine, abscisic acid, kinetin, and indole-3-acetic acid, applied in appropriate concentrations, combinations, and durations, makes possible the selective blockade of the cell cycle in G₁, G₂, any mitotic stage, and between karyokinesis and cytokinesis. Moreover, treatment with abscisic acid followed by a recovery period stimulates polyploid nuclei in mature tissues to divide. Colchicine, kinetin, and indole-3-acetic acid applied together cause end-to-end association of metaphase chromosomes. These results together with earlier findings suggest that any step of the cell cycle is independently controlled both by specific balance of the growth regulators and by specific synthesis of the nucleic acids.     

Analysis of the C-banded karyotype of Allium cepa L. Standard system of nomenclature and polymorphism

The C-banded karyotypes of three Allium cepa plants of different background are described. Identification of all chromosomes of Allium cepa is possible on the basis of complex telomeric and intercalary C-bands. A standard system of chromosome nomenclature is proposed. Infraspecific variation in heterochromatin amount per genome, number of intercalary bands per genome, relative area of telomeric bands, relative chromosome length, relative chromosome arm length and centromeric index are statistically analysed. Although extensive polymorphism in Allium cepa chromosomes is found especially with respect to the size of telomeric bands, the overall similarity of the karyotypes is obvious. The value of C-banding for biosystematics of cultivated plants related to Allium cepa and for their breeding is suggested.