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.     

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.     

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.     

CYTOGENETICS OF AGROPYRON FERGANENSE AND ITS HYBRIDS WITH SIX SPECIES OF AGROPYRON,ELYMUS, AND SITANION

Meiosis and mode of reproduction are described in Agropyron ferganense Drob., a perennial forage grass from Central Asia. This species is diploid (2n = 14); it exhibits normal meiosis and reproduces by cross-pollination. Hybrids were produced between A. ferganense and six species with known genome formulas: 1) North American A. spicatum (Pursh) Scribn. & Smith, an SS diploid (2n = 14), 2) Middle Eastern A. libanoticum Hack., an SS diploid (2n = 14), 3) North American A. dasystachyum (Hook.) Scribn., an SSHH tetraploid (2n = 28), 4) Eurasian A. caninum (L.) Beauv., an SSHH tetraploid (2n = 28), 5) North American Sitation hystrix (Nutt.) J. G. Smith, an SSHH tetraploid (2n = 28), and 6) South American Elymus patagonicus Speg., an SSHHHH hexaploid (2n = 42). Almost complete chromosome pairing in the A. ferganense x A. spicatum and A. libanoticum hybrids demonstrated that A. fergenanse is an SS diploid, but it is genetically isolated from the other SS diploids because of high sterility in the F₁ hybrids. S-genome diploids form a network of species that extend from the Middle East through Central Asia to western North America. Frequent occurrence of seven univalents and seven bivalents at metaphase I in the triploid hybrids of A. ferganense x A. dasystachyum, A. caninum and S. hystrix was consistent with the proposed genome formulas of SS for A. ferganense, SSHH for the three tetraploid species, and SSH for the hybrids. Chromosome pairing was highly variable in the A. ferganense x E. patagonicus hybrids; however, some cells had almost complete bivalent pairing, an expected observation in an SSHH hybrid from a cross between an SS diploid (A. ferganense) and an SSHHHH hexaploid (E. patagonicus). Various options were considered concerning the appropriate generic classification of the S-genome diploids, which are now commonly placed in Agropyron. The inclusion of these species in the genus Eiytrigia, as advocated by some Soviet taxonomists, appears to be a reasonable decision.     

Were the main mountain ranges in the Korean Peninsula a glacial refugium for plants? Insights from the congeneric pair Lilium cernuum – Lilium amabile

The main Korean mountain range (the so-called “Baekdudaegan”), which stretches from north to south across most of the country, has been thought to harbor glacial refugia for boreal plant species, where they likely found relatively stable habitats and maintained large population sizes. Under this scenario, high levels of genetic variation and low or moderate degree of differentiation among populations within these species were expected. To test this hypothesis, we examined levels of allozyme diversity (14 loci) in eight populations of the boreal herb Lilium cernuum, which in Korea occurs largely along the Baekdudaegan and, as a reference, in eight populations of its congener Lilium amabile, a temperate species that is distributed on lower hillsides in peripheral regions of the Baekdudaegan. L. cernuum harbored higher levels of genetic variation within populations than L. amabile (%P = 49.1 vs. 25.0, A = 1.71 vs. 1.34, and H_e = 0.159 vs. 0.048). Genetic differentiation among populations was low for both species (F_ST = 0.119 and 0.014 for L. cernuum and L. amabile, respectively). A series of historical and ecological factors may explain the contrasting levels of genetic diversity between L. cernuum and L. amabile: occurrence within the main ranges of the Baekdudaegan (enduring the glacial periods in macrorefugia) vs. low elevation peripheral areas (in microrefugia) and shade-tolerant vs. shade-intolerant. This study, as well as previous population genetics studies, strongly suggests that the Baekdudaegan merits high priority for conservation given its proposed role as glacial refugia for montane species.     

CHROMOSOME NUMBERS IN CENCHRUS (GRAMINEAE)

Gametic chromosome numbers are reported for 22 populations representing 6 taxa in the genus Cenchrus. Numbers of n = 17 were obtained for C. incertus M. A. Curtis, C. longispinus (Hack.) Fern., and for the previously unreported C. mitis Anderss. Populations of C. echinatus L. have the number n = 34, and C. myosuroides H.B.K. n = 35. Irregular meiosis was observed in 2 chromosomal races of C. ciliaris L. having numbers of n = 18 and n = ca. 16, respectively.     

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.     

GENETIC DIFFERENTIATION AND HYBRIDIZATION BETWEEN CAREX GYNODYNAMA AND C. MENDOCINENSIS (CYPERACEAE) IN CALIFORNIA

Patterns of variation within and between Carex gynodynama and C. mendocinensis were investigated by studying allozyme and chromosome variation in natural populations and structural variation using herbarium specimens. Multivariate analyses of structural data demonstrated that C. gynodynama is clearly distinct from C. mendocinensis, and that sterile specimens similar to C. mendocinensis are intermediate between that species and C. gynodynama. The mean genetic distance between the two species, based on allozyme phenotypes at 17 enzyme-coding loci, was 0.22 ± 0.12. The sterile putative hybrids had the expected heterozygous pattern at three enzyme-coding loci at which the parental species were fixed for different alleles. Chromosome numbers are reported for the first time for both species and their putative hybrid. Carex mendocinensis had a different number in each of the three populations examined with n = 28, n = 29, or n = 30. Chromosome counts from one population of C. gynodynama revealed five plants with n = 25 and one with n = 26. Putative hybrids from this population exhibited irregular pairing at meiosis with 2n = ca. 55–57. Patterns of allozyme variation also suggest that C. mendocinensis has an outcrossing or mixed mating system but that C. gynodynama is an inbreeding species. Carex gynodynama exhibited very little variation in structure, habitat, or at the enzyme-coding loci examined, suggesting that it may have experienced a genetic bottleneck relatively recently. Carex mendocinensis had higher levels of variation both within and between populations at enzyme-coding loci and in structural features. This pattern of variation and a geographic distribution centered in serpentine areas of the Klamath–Siskiyou region, with disjunct smaller populations in serpentine areas farther south, suggest that C. mendocinensis once may have been a more widespread species.     

Allotetraploid origin ofAllium altyncolicum (Alliaceae, Allium sect.Schoenoprasum) as investigated by karyological and molecular markers

The tetraploidAllium altyncolicum (2n = 4x = 32) is considered to be of hybrid origin, because most of its morphological characters are intermediate between those of its putative parents,A. schoenoprasum andA. ledebourianum. In the present work an attempt has been made to ascertain its parentage by several methods: Giemsa C-banding, genomic in situ hybridization (GISH), PCR-RFLP of cpDNA, restriction enzyme mapping of the rDNA, and RAPDs. C-banding and GISH indicates clearly thatA. altyncolicum is a segmental allopolyploid.Allium schoenoprasum andA. ledebourianum are the most likely the parental species and the larger part of the genome ofA. altyncolicum (26 chromosomes) is derived fromA. schoenoprasum. The low genetic divergence between these three species was confirmed by the lack of sequence variation in the ITS sequences of nuclear rRNA genes and of the plastid rbcL-atpB intergenic spacer. Both parental species andA. altyncolicum could be distinguished by RFLP of the rDNA repeats. The geographic origin of the putative parental species was investigated using RAPDs.Dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer on the occasion of his 70th birthday     

Meiotic restriction in emmer wheat is controlled by one or more nuclear genes that continue to function in derived lines

Highly fertile F₁ hybrids were made between Triticum turgidum L. ssp. turgidum (2n = 28, AABB) and Aegilops tauschii Coss. (2n = 14, DD) without embryo rescue and hormone treatment. The F₁ plants had an average seed set of 25%. Approximately 96% of the F₂ seeds were able to germinate normally and about 67% of the F₂ plants were spontaneous amphidiploid (2n = 42, AABBDD). Cytological analysis of male gametogenesis of the F₁ plants showed that meiotic restitution is responsible for the high fertility. A mitosis-like meiosis led to meiotic restitution at either of the two meiotic divisions resulting in unreduced gametes. Test crosses of the T. t. turgidum–Ae. tauschii amphidiploid with Ae. variabilis and rye suggested that the mitosis-like meiosis is controlled by one or more nuclear genes that continue to function in derived lines. This discovery indicates a potential application of such genes in producing double haploids.     

CYTOTAXONOMIC STUDIES IN ELEOCHARIS SUBSER. PALUSTRES: CENTRAL UNITED STATES TAXA

Comparative chromosomal and morphological studies indicate that four species are present in the area surveyed. Eleocharis smallii Britt. is primarily diploid with 2n = 16, although sporadic polyploids with 2n = 36 also occur. E. macrostachya Britt. is morphologically similar with unstable polyploid numbers ranging around 2n = 38 and multivalents and univalents present in meiosis. E. xyridiformis Fern. & Brack., a species generally synonymized with E. macrostachya, is shown to be a morphologically distinct species with 2n = 18, 19, and 20. The 19-chromosome types are trisomic for one of the long chromosomes, the three homologs pairing in meiosis as a large chain trivalent. The trivalent separates equationally in the first division and preferentially in the second so that only 9- or 10-chromosome pollen grains containing an extra chromosome are formed. Trisomic cytotypes may potentially produce normal (18), reconstituted trisomies (19), or tetrasomic (20) plants, although tetrasomics have not been found. The 20-chromosome cytotype is not the expected tetrasomic, as it is karyotypically distinct from either the 18 or 19 cytotypes. In all species somatic mutations including translocations, translocation-retranslocations, and chromosome fragmentation (agmatoploidy) have been observed of which the significance, if any, has not been determined.     

Cytomorphological studies in some members of tribe Paniceae (Poaceae) from district Kangra of Himachal Pradesh (Western Himalayas)

The present paper deals with cytological studies on the population basis of 21 species belonging to 9 genera of tribe Paniceae of family Poaceae from cytologically unexplored area of Western Himalayas i.e. district Kangra of Himachal Pradesh for the assessment of genetic diversity of grass flora. On world-wide basis, the chromosome counts have been made for the first time for three species such as Brachiaria remota (n = 16), Digitaria granularis (n = 36) and Isachne albens (n = 5). Similarly, on India basis, altogether new records are made for two species such as Echinochloa cruspavonis (n = 27) and Paspalum distichum (2n = 50). A comparison of the different euploid cytotypes studied at present for Digitaria adscendens, D. setigera and Oplismenus compositus revealed significant variations in their morphology, depicting increase in some of the characters of polyploid cytotypes. The course of meiosis has been observed to be normal in all the studied populations with high pollen fertility except for two species such as Paspalum dilatatum and P. distichum marked with abnormal meiosis and reduced pollen fertility.     

BIOSYSTEMATIC INVESTIGATIONS IN THE GENUS AGROPYRON. I. CYTOLOGICAL STUDIES OF SPECIES KARYOTYPES

Schulz -Schaeffer , Jurgen (Montana State Coll., Bozeman), and Peter Jurasits . Biosystematic investigations in the genus Agropyron. I. Cytological studies of species karyotypes. Amer. Jour. Bot. 49(9): 940–953. Illus. 1962.—Twenty-five species of the genus Agropyron are analyzed cytologically in this presentation. Accession numbers, names of collectors, locations where seed was collected, and observed chromosome numbers are listed. Chromosome numbers of A. panormitanum (2n = 28), A. lolioides (2n = 58), A. brachyphyllum (2n = 42), A. ciliatiflorum (2n = 28), A. kosanini (2n = 56), A. pseudorepens (2n = 28), A. squamosum (2n = 42), and A. subulatum (2n = 56) are reported. No previous counts in these species are known to the authors. Chromosome counts of A. caespitosum (2n = 42) and A. elongatiforme (2n = 58), deviate from previous reports. Idiograms of all species and photomicrographs of mitotic metaphase root tip cells of 14 species are presented. The distribution of 11 satellite-chromosome types in 25 Agropyron species is shown in Table 2. The proportions of these 11 satellite-chromosome types are recorded in Table 3. The significance of these satellite chromosomes as indicator chromosomes for genome relationships is discussed together with the pertinent literature.     

Cytogenetics of tropical bulbous ornamentals VIII: Pollen grain mitosis in Zephyranthes puertoricensis

The immediate result of recombination during male meiosis within the complex interchange heterozygote polyploids in Zephyranthes could be assessed from the chromosomal constitution of pollen grains in one species with 2n=25. The numbers found in the pollen grains were n=1–16, 20 and 24. Considering n=12 (22.3%) as the haploid number, nearly 57.2% were subhaploid, out of which 19.6% had n=11. Occurrence of such a high proportion of subhaploid grains may be explained on the basis of the polyploid constitution (4x+1) of the species (x=6). In this sense, grains with a basic set of 6 chromosomes may be able to function. Therefore, in the real sense only grains with numbers less than 6 are submonoploid which constitute only 10.7%. In the subhaploid grains there was a preference for large and medium sized chromosomes, while in grains with higher numbers there was noted a tendency for smaller chromosomes to be represented more than once, indicating their non-disjunction during meiosis. Totally new types of nucleolar chromosomes emanating after recombination were also seen.This investigation has shown the extent of potential cytological polymorphism possible in heterozygotes like Zephyranthes puertoricensis. How much of this polymorphism is meaningful in creating the aneuploid pattern found in the genus, depends on the competitive advantage different numbers have during fertilisation vis-a-vis possibly similar polymorphism created during the female meiosis.     

NUMBERS AND DISTRIBUTIONS OF VASCULAR BUNDLES IN SCAPES OF THREE ALLIANCES OF THE GENUS ALLIUM L. (LILIACEAE)

The arrangement and numbers of vascular bundles were documented for the species of the Allium cernuum Roth, Allium validum Wats., and Allium kunthii G. Don alliances. These characters proved consistent and diagnostically useful in the A. cernuum and A. validum alliances, but inconsistent in the A. kunthii alliance.     

Inter and intra-specific hybridization in tuco-tucos (Ctenomys) from Brazilian coastal plains (Rodentia: Ctenomyidae)

The present work describes chromosomal polymorphisms in zones of contact between divergent populations of Ctenomys minutus parapatrically distributed in the coastal plain of southern Brazil, and inter-specific hybridization with C. lami a closely related species. A sample of 171 specimens from 32 sample sites distributed along 161 km of the coastal plain was cytogenetically analyzed. Nine polymorphic populations were found: four with specimens with 2n = 46–48 (autosomal arm number (AN) = 76); three only have specimens with 2n = 47 and 48; one population sampled presented specimens with 2n = 43–46 (AN = 74–76) and one population with 2n = 50–52 (AN = 76–80). The remainder populations were fixed for 2n = 42, 46 or 48. The variation is the result of Robertsonian mechanisms of chromosomal evolution and a fusion in tandem rearrangement. The polymorphisms have been considered the result of secondary contact of populations after divergence in allopatry. The geomorphological evolution of the coastal plain provides clues to the possible existence of past geographic barriers acting over populations of Ctenomys, during the Holocene.     

Chromosome numbers of Turkish Crocus (Liliiflorae,Iridaceae) and their geographical distribution

The genus Crocus is known for its widely varying chromosome numbers (from 2n = 6 to 2n = 70) with varying numbers occurring even within species, as it is the case for Crocus biflorus Miller (2n = 8, 10, 12, 14, 16, 18, 20, 22, 24). After we found morphological diverse C. biflorus populations in Turkey doubts arose about their rank of being subspecies of the Italian C. biflorus (2n = 8). Here we publish the chromosome numbers for 76 populations of C. biflorus sensu lato distributed all over Turkey. The chromosome numbers ranged from 2n = 8 to 2n = 36, with the higher numbers occurring in the mountain ranges of the Anatolian Diagonal and east of it, while lower numbers were found only southwest of these mountains. Closely related taxa with similar distribution mostly differ in their chromosome numbers. This led us to assume that chromosomal changes influence speciation processes in the genus. Therefore, chromosome numbers may represent an important character for the establishment of a new taxonomic treatment of the Crocus species, especially within section Nudiscapus. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

CHROMOSOME ANALYSIS OF HYBRIDS BETWEEN 4N GRINDELIA CAMPORUM AND 2N G. GRANDIFLORA (COMPOSITAE)

Morphology and meiosis are described in four progeny plants resulting from tetraploid Grindelia camporum Greene (2n = 24) from California pollinated by diploid G. grandiflora Hook. (2n = 12) from Coahuila, Mexico. Three of the four progeny were tetraploid, morphologically like the pistillate parent, and had metaphase I chromosome configurations which included quadrivalents and a complementary number of bivalents. They are considered to have resulted from selfing. The fourth plant was triploid (2n = 18) andmorphologically intermediate between the parents. Chromosome configurations in the triploid were variable with univalents, ring and rod bivalents, trivalents and pentavalents. These two species are considered related through an ancestor with a basic genome, but are separated cytologically by polyploidy and by two distinct chromosomal interchanges that explain the configurations observed in the triploid hybrid.     

Contribution to the cytotaxonomy of Oryzopsis (Poaceae)

Meiotic studies were performed in twelve populations of four Oryzopsis species (O. pubiflora, O. lateralis, O. holciformis var. longiglomis and O. barbellata) to obtain data on the ploidy level and cytological evolution of the genus. The chromosome number 2n=2x=24 was revealed in all the species and populations studied. The present and other studies show the occurrence of two basic chromosome numbers in the genus, i.e. x=11 and x=12. Although Oryzopsis species and populations studied are diploid and are expected to form only bivalents in metaphase of meiosis‐I, quadrivalents were observed in O. pubiflora and O. lateralis, possibly due to the occurrence of heterozygote translocations. B‐chromosomes of 0–2 were observed in all species and populations studied. This is the first report of the occurrence of B‐chromosomes in the genus Oryzopsis. Several meiocytes showed the presence of double chromosome number in O. lateralis, and multipolar cells were observed in populations of O. barbellata, O. lateralis and O. holciformis var. longiglomis. The occurrence of large pollen grains (possibly unreduced) was observed along with smaller (normal) pollen grains in these species. Significant differences observed in chiasma frequency and distribution among studied species may be of use in species delimitation. The Kakan population differed significantly from the other populations of O. lateralis in meiotic characteristics. If such cytological differences are accompanied by morphological variation (under investigation), we may consider this population as a new variety or subspecies.